Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
PART
I
INTRODUCTION TO LIVING ANIMALS
1
2
3
4
Life: Biological Principles and the Science of Zoology ..... 1
The Origin and Chemistry of Life ...................................... 8
Cells as Units of Life .......................................................... 15
Cellular Metabolism ........................................................... 25
____________________________________________________________________________________________
CHAPTER
1
LIFE: BIOLOGICAL PRINCIPLES
AND THE SCIENCE OF ZOOLOGY
CHAPTER OUTLINE
1.1.
1.2.
The Uses of Principles (Figure 1.1)
A. Underlying Principles Central to Understanding Zoology
1. Laws of physics and chemistry underlie some zoology principles.
2. Principles of genetics and evolution guide much zoological study.
3. Principles learned from one animal group can be applied to others.
4. Some science methods specify how to conduct solid research.
B. Zoology, the Study of Animal Life
1. Zoologists studying many dimensions base research upon a long history of work.
2. Two central principles are evolution and the chromosomal theory of inheritance.
Fundamental Properties of Life
A. Defining Properties of Life
1. Properties exhibited by life today are different from those at its origin.
2. Change over time, or evolution, has generated many unique living properties.
3. Definitions based on complex replicative processes would exclude non-life, but also early forms
from which cellular life descended.
4. We do not force life into a simple definition, yet we can readily recognize life from a nonliving
world.
B. General Properties of Living Systems
1. Chemical Uniqueness (Figure 1.2)
a. Macromolecules in organisms are far more complex than molecules in nonliving matter.
b. They obey the same physical laws as nonliving molecules but are more complex.
c. Nucleic acids, proteins, carbohydrates and lipids are common molecules in life.
d. Their general structure evolved early; thus the common amino acid subunits of proteins are
found throughout life.
e. They provide both a unity based on living ancestry and a potential for diversity.
2. Complexity and Hierarchical Organization (Figures 1.3, 1.4; Table 1.1)
a. Life has an ascending order of complexity: macromolecules, cells, organisms, populations and
species.
b. Each of these levels has an internal structure: macromolecules form ribosomes and
membranes, etc. and cells form tissues.
c. However, each level has unique abilities and requirements; cells can replicate but are not
independent in an organism.
d. New characteristics that appear at the next level of organization are emergent properties.
e. Because of the interactions of the components, we must study all levels directly as well as
together.
f. Diversity of emergent properties at higher levels is a result of evolution (i.e. lower levels
without hearing cannot develop language).
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
3. Reproduction (Figure 1.5)
a. Life comes from previous life but had to arise from nonliving matter at least once.
b. Genes replicate genes, cells divide to produce new cells and organisms produce new
organisms sexually or asexually.
c. Reproduction is not necessary of individuals, but is necessary for a lineage to survive.
d. Reproduction is a combination of contradictory processes of copying traits, but with variation.
e. If heredity were perfect, life would never change; if it were wildly variable, life would lack
stability.
4. Possession of a Genetic Program (Figure 1.6)
a. Structures of protein molecules are encoded in nucleic acids.
b. Genetic information in animals is contained in DNA.
c. Sequences of nucleotide bases (A, C, G and T) code for the order of amino acids in a protein.
d. The genetic code is correspondence between bases in DNA and sequence of amino acids.
e. This genetic code was established early in evolution and has undergone little change.
f. The genetic code in animal mitochondrial DNA is slightly different from nuclear and bacterial
DNA.
g. Changes in mitochondria DNA (it contains fewer proteins) are less likely to disrupt cell
functions.
5. Metabolism (Figure 1.7)
a. Living organisms maintain themselves by obtaining nutrients from the environment.
b. Breakdown of nutrients provides both energy and molecular components for cells.
c. Metabolism is the range of essential chemical processes.
d. Metabolism involves constructive (anabolic) and destructive (catabolic) reactions.
e. Most metabolic pathways occur in specific cell organelles.
f. The study of the performance of complex metabolic functions is physiology.
6. Development (Figure 1.8)
a. Development describes characteristic changes an organism undergoes from origin to adult.
b. It involves changes in size and shape, and differentiation within the organism.
c. Some animals have uniquely different embryonic, juvenile and adult forms.
d. The transformation from stage to stage is metamorphosis.
e. Among animals, early stages of related organisms are more similar.
7. Environmental Interaction (Figure 1.9)
a. Ecology is the study of an organism's interaction with the environment.
b. Organisms respond to stimuli in the environment, a property called irritability.
c. We cannot separate life and its evolutionary lineage from its environment.
C. Life Obeys Physical Laws
1. Vitalism is the belief that life requires more than basic laws of physics; biological research has
found no basis for vitalism.
2. First Law of Thermodynamics (the law of conservation of energy)
a. Energy cannot be created or destroyed; it can be transformed from one form to another.
b. All aspects of life require energy.
c. In animals, chemical energy in food is converted to chemical energy in cells and then
converted to mechanical energy of muscle contraction.
3. Second Law of Thermodynamics
a. Physical systems tend to proceed toward a state of greater disorder, or entropy.
b. Energy obtained and stored by plants is released in many ways and eventually lost as heat.
c. It takes a constant input of usable energy from food to keep an animal organized.
d. The process of evolution does not violate the second law; complexity is achieved by constant
use and dissipation of energy flowing into the biosphere from the sun.
e. Physiologists study survival, growth, reproduction, etc. from an energetic perspective.
1.3.
Zoology as a Part of Biology (Figure 1.10)
A. Characteristics of Animals
1. Animals are a branch of the evolutionary tree of life.
2. Animals are part of a large limb of eukaryotes, organisms that include fungi and plants with nuclei
in cells.
3. Animals are unique in nutrition; they eat other organisms and therefore need to capture food.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
4. Animals lack photosynthesis, cell walls found in plants, and also lack absorptive hyphae of fungi.
5. Species of Euglena are examples of protists that combine properties of animals and plants.
1.4.
Principles of Science
A. Nature of Science
1. Science is a way of asking about the natural world to obtain precise answers.
2. Asking questions about nature is ancient; modern science is about 2000 years old.
3. Science is separate from activities such as art and religion.
4. The trial over creation science provided a definition of science.
a. Science is guided by natural law.
b. Science has to be explanatory by reference to natural law.
c. Science is testable against the observable world.
d. Science conclusions are tentative; they are not necessarily the final word.
e. Science is falsifiable.
5. Science is neutral regarding religion and does not favor one religious position over another.
B. Scientific Method (Figure 1.11)
1. Criteria for science form a hypothetico-deductive method.
2. Hypotheses are based on prior observations of nature or derived from theories based on nature.
3. Testable predictions are made based on hypotheses.
4. A hypothesis powerful in explaining a wide variety of related phenomena becomes a theory.
5. Falsification of a specific hypothesis does not necessarily lead to rejection of a theory as a whole.
6. The most useful theories explain the largest array of different natural phenomena.
7. Scientific meaning of “theory” is not the same as common usage of theory as “mere speculation.”
8. Powerful theories that guide extensive research are called paradigms.
9. Replacement of paradigms is a process known as a scientific revolution; the evolutionary
paradigm has guided biology research for over 130 years.
C. Experimental Versus Evolutionary Sciences
1. Questions can be divided into those that seek to understand proximate versus ultimate causes.
2. Studies that explore proximate causes are experimental sciences using experimental methods that:
a. Predict how a system being studied will respond to disturbance or treatment,
b. Make the disturbance, and then
c. Compare the observed results with predicted ones.
3. Controls are repetitions of an experiment that lack disturbance or treatment.
4. The sub-fields of molecular biology, cell biology, endocrinology, developmental biology and
community ecology rely heavily on experimental scientific methods.
5. Ultimate causes are addressed by questions involving long-term timespans.
a. Evolutionary sciences address ultimate causes.
b. Evolutionary questions are often explored using a comparative method.
c. Patterns of modern similarities are used to establish hypotheses on evolutionary origins.
d. Sub-fields include comparative biochemistry, molecular evolution, comparative cell biology,
comparative anatomy, comparative physiology and phylogenetic systematics.
1.5.
Theories of Evolution and Heredity (Figure 1.12-1.15)
A. Darwin’s Theory of Evolution
1. Ernst Mayr describes five central theories of “Darwinism.”
a. Perpetual change: changes across generations are a fact documented in the fossil record.
b. Common descent: branching lineages form a phylogeny that is confirmed by expanding
research on morphological and molecular similarities.
c. Multiplication of species: splitting and transforming species produces new species.
d. Gradualism: small incremental changes over long periods of time cause gradual evolution, but
current research is still studying if this explains all changes.
e. Natural selection: based on variability in a population, the inheritance of that variation, and
different survival of those variants, explains adaptation.
2. Darwin lacked a correct theory of heredity and assumed the current theory of blending inheritance
was correct; Mendel’s theory of particulate inheritance became well known only in the very early
1900s.
3. Darwin’s theory as modified by incorporation of genetics is called “neo-Darwinism.”
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
B. Mendelian Heredity and the Chromosomal Theory of Inheritance (Figure 1.16)
1. Chromosomal inheritance is the foundation for genetics and evolution, as laid down by Mendel.
2. Genetic Approach (Figure 1.17-1.19)
a. Mendel’s technique involved crossing true-breeding populations.
b. Production of F1 hybrids and F2 generations showed lack of blending, and masking of
recessive traits by dominant traits.
c. Traits assorted independently unless on the same chromosome.
d. Expanded research, especially with fruit flies, clarified genetic mechanisms.
3. Contributions of Cell Biology
a. Improvements in microscopes allowed observation of sperm and location of germ cell line.
b. Discovery of chromosome pairs in body cells and single sets in germ cells clarified mode of
heredity.
Lecture Enrichment
1.
2.
3.
4.
5.
6.
7.
8.
9.
From the Australian outback to interior New Guinea, all cultures regardless of science education level
distinguish living from nonliving substances. Although this is the first day of classes and students may not have
had an opportunity to read the assigned text, they can be led through a query of "what is life?" They will
usually offer: growth, reproduction, response to the environment, metabolism, etc. Ask whether any one of
these aspects alone distinguishes a living organism from nonliving organism. Note that it is not necessary for
an individual organism to reproduce, and indeed most animals hatched or born do not survive to reproduce.
Clay is an example of self-replicating molecular assemblages that do not have the potential variety or the
metabolism to be called living. Quartz is a molecule that can “grow,” “reproduce” and “respond” to light.
Tardigrades can completely suspend metabolism for a century and dehydrate to ten percent of their living water
content. These examples will appropriately muddle the definition of life. Nevertheless, it is critical in deciding
that if we find life on Mars–would we recognize it? We continue attempts to confirm whether life has ever
existed on Mars. What phenomena would we look for?
Levels of organization can seem rather abstract. Read job descriptions for biologists (e.g., histologist,
population geneticist, community ecologist, etc.). Ask students what level of organization the scientist studies.
Virtually continuously throughout this course, students can be asked to design an experiment to test a particular
hypothesis being discussed.
Ask students for examples of the scientific method in their everyday lives, such as fixing dinner, determining
how to dress for the day's weather and activities, or handling problems with a car that doesn’t work.
Students can search local newspapers for examples using the scientific method (e.g. testing consumer products,
recalls, reports on medical research, jury decisions based on forensic evidence, etc.). Bring in a tabloid
newspaper making fabulous claims and ask why it does not meet science standards.
Discuss the difference between scientific observations of the natural world and superstitions such as those
associated with Friday the thirteenth and black cats. Examples involving Bigfoot, the Loch Ness Monster,
spontaneous human combustion, living dinosaurs in remote areas, and other modern misbeliefs related to
animals are given in the Skeptic and Skeptical Inquirer magazines.
Discuss why it is possible to prove a hypothesis or theory false but not prove it true. Be careful not to fall into
the postmodernist or constructivist view of science knowledge being merely a mental construct, no better or
worse than tribal beliefs, etc. or being tentative to the point of merely awaiting falsification.
Most students believe the world is spherical. Only students who have flown in the Concorde jetliner have direct
observational evidence for this. Yet they believe the photos by astronauts, and phoning a person in China
awakes them in a time zone 12 hours different from us. Such indirect evidence fortifies the model of a spherical
earth. This illustrates science relies on reasoning to make sense of observational data.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Commentary/Lesson Plan
Background: Professors that are new to a college or university may consult with veteran professors about the state’s
high school biology and other science requirements. In addition, the proportion of students that come from farm or
urban backgrounds will provide a major indicator of student experiences. Most high school science texts discuss the
“scientific method” as a very cookbook or lock-step method. And most college undergraduates do not have genuine
experience with open-ended and purposeful science research, nor the breadth of experience to place limited research
experience in a full perspective.
Misconceptions: Many students see science as a body of encyclopedic knowledge and authority, and do not
recognize an underlying scientific attitude or process. Some students have been told that science is only process,
and have no appreciation for the role of the general public recognizing germ theory, for instance. Most citizens view
science practiced only by scientists and do not consider the trouble-shooting performed by a medical doctor or
mechanic to be in any way “scientific.” Most consider scientists always “open minded” and do not recognize that
experiments often close the door to hypotheses that don’t work out. In many states, physics classes are not
commonly taken in high school; this may be their first exposure to physics and many students will misunderstand
the laws of physics as preventing evolution. A large portion of college students believe that dinosaurs and humans
were on earth at the same time, and a similar proportion question the validity of the theory of evolution without
much depth of knowledge about it. A large proportion view evolution as “survival of the fittest” without
recognizing that survival is only useful if it promotes reproduction.
Schedule: Students may lack the book assignment the first day of class, but this is the point where an instructor
establishes the ground rules of quizzes, testing, whether notes will be given in outline form, etc. If you use in-class
questioning, beginning with “What is Life?” as in Lecture Enrichment #1 above, which can set the pace.
HOUR 1 1.1.
1.2.
1.3.
HOUR 2 1.4.
1.5.
The Uses of Principles
A. Underlying Principles Central to Understanding Zoology
B. Zoology, the Study of Animal Life
Fundamental Properties of Life
A. Defining Properties of Life
B. General Properties of Living Systems
C. Life Obeys Physical Laws
Zoology as a Part of Biology
A. Characteristics of Animals
Principles of Science
A. Nature of Science
B. Scientific Method
C. Experimental Versus Evolutionary Sciences
Theories of Evolution and Heredity
A. Darwin’s Theory of Evolution
B. Mendelian Heredity and the Chromosomal Theory of Inheritance
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
ADVANCED CLASS QUESTIONS:
1. Recent satellite probes as well as meteorite discoveries have been used to search for the possibility of life on
Mars. What properties would scientists look for in currently living life forms? If life once existed but became
extinct, what evidence would still exist that life once existed?
2. Scientists use the scientific method to gather information about the natural world. Can this include the past?
Does how a forensics expert reconstructs a crime scene differ in substance from how an evolutionary biologist
reconstructs ancient ecology from fossil evidence?
3. When utilizing the scientific method, hypotheses can be proven false, but not true. Does this mean all science is
conjecture until disproven? Can anyone explain the “uncertainty principle” and the ability of scientists to
calculate the tolerance limits of their knowledge?
4. What evidence exists that all living things evolved from a common ancestor? How does this concept explain
the unity of life forms?
5. Animal ecology experiments can be classified in two general categories: Ecologists can bring an animal into
the laboratory, isolate it in a chamber where they can determine all the environmental conditions affecting it and
then alter one variable. Or, they can study the animal in the wild and attempt to determine why it occurs in
certain natural habitats. Using terms given in the text for science methodology, explain the benefits of both
systems.
Twelfth Edition Changes:
Outside of minor editorial changes, there are no major additions or deletions
to this chapter. References and Zoology Links to the Internet have been updated.
1.
A new reference by F.M. Loew (1995) concerning the animal rights controversy has been added.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Source Materials
[Bold = recommended; for vendor abbreviations, see list of distributors in Appendix 1.]
All About Science II (Q), Mac, MS-DOS CD
The Best Mind Since Einstein (WGBH), 60-min. video
Biologists at Work (HH), 44-min. video
Biology Flash Series (PLP), MS-DOS
Biology: Form and Function (CPB), 12 24-min. videos
Biology: The Study of Life (CAM) (CYBER), Mac, MS-DOS CD
BioQUEST 3.0 (CPB), Mac CD
The BioQuest Library V (A-CPB), 54 Mac modules and 25 Win modules on CD
Bio Sci II (VDISC) laserdisc
A Brief History of Biology (HH), 18-min. video
Clinical Trials (FH), 25-min. video
Comprehensive Review in Biology (Q), Mac, MS-DOS CD
Cycles of Life: Exploring Biology–The Unity and Diversity of Life (A-CPB), 26 30-min. videos
Energy Flow in the Ecosystem (FH), 10-min. video
Experiment: Biology Series (CBSC), 6 15-min. videos
The Experimental Conditions (UC), 36-min. video
Exploring Biology: Careers and Issues (CYBER), Mac, MS-DOS CD
Five Kingdoms of Life Series, The (CBSC), Mac, Win, MS-DOS CD
General Biology Data Simulation (OAK), MS-DOS and Mac, video
Generation Upon Generation [Ascent of Man Series] (AVP), 52-min. video
God, Darwin, and Dinosaurs (WGBH), 60-min. video
Introduction to General Biology Series (FISH), Mac, MS-DOS
Knowledge or Certainty [Ascent of Man Series] (AVP), 52-min. video
Learning All About Cells and Biology (Q), Mac, Win CD
Life Itself (FH), 23-min. video
The Multimedia Book of Biology Concepts (PLP), MS-DOS
NOVA: The Bermuda Triangle (WGBH), 60-min. video
NOVA: The Best Mind Since Einstein (WGBH), 60-min. video
NOVA: Kidnapped by UFO’s? (WGBH), 60-min. video
NOVA: Last Journey of a Genius (WGBH), 60-min. video
NOVA: Secrets of the Psychics (MBI) (WGBH), 60-min. video
NOVA: UFO’s–Are We Alone? (MBI) (WGBH), 60-min. video
NTSYS-pc (SciT), Mac, MS-DOS
Powers of Ten (PYR), 10-min. video [levels of organization]
Preserving the Rain Forest (FH), 24-min. video
Scientific Method (EVN), video
The Scientific Method, Graphs and Statistics (PLP), MS-DOS
Scientific Methods and Values (HH), 34-min. video
SimLife (FISH), Mac, MS-DOS
The Soul of Science (HH), 4-parts total 78-min. video
Statistics and the Sciences (FH), 25-min. video
Survey of Biology (JLM), slide set (200)
TAADS (INT), Mac
Think For Yourself: Critical Thinking on Pivotal Issues of Our Time (INT) CD, Mac
Thinking Like a Scientist (GA), CD, Mac
Through Fish Eyes (FH), 30-min. video
The Tropical Rain Forest (FH), 28-min. video
Urban Ecology (FH), 24-min. video
When Scientists Cheat (WGBH), 60-min. video
Why Use Statistics? (FH), 4-part series of 20-25-min. videos
Women in Science (HH), 33-min. video
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
CHAPTER
2
THE ORIGIN AND CHEMISTRY OF LIFE
CHAPTER OUTLINE
2.1.
2.2.
Spontaneous Generation of Life
A. History
1. Spontaneous generation was a belief that frogs could arise from earth, mice from rotten matter,
etc.
2. In 1861, Louis Pasteur demonstrated sterilized broth in flasks, even exposed to air, could not
spontaneously ferment.
3. However, Oparin and Haldane independently proposed a long period of “abiotic molecular
evolution” stating life did once arise from nonliving chemistry. (Figure 2.1)
Organic Molecular Structure of Living Systems
A. Carbon
1. Organic compounds contain carbon; most are produced in living systems.
2. Over one million carbon-based molecules have been identified.
B. Carbohydrates: Nature’s Most Abundant Organic Substance
1. Carbohydrates contain carbon, hydrogen and oxygen, usually in ratio of 1C:2H:1O as H–C–OH.
2. Carbohydrates provide structural elements and store energy.
3. Glucose is commonly found in the blood of animals and is an important immediate energy source
for cells (Figure 2.2)
4. Cellulose occurs in greater quantities than all other organic materials combined.
5. Carbohydrates, synthesized by plants by photosynthesis, are the starting point of food chains.
6. Monosaccharides (Figure 2.3)
a. Monosaccharides are simple sugars with a carbon backbone of four, five or six carbon atoms.
b. Glucose, galactose and fructose all contain free sugar groups.
c. The hexose glucose is particularly important in life.
7. Disaccharides (Figures 2.4, 2.5)
a. Disaccharides contain two monosaccharides bonded together.
b. Maltose is formed from the bonding of two glucose molecules and removal of a water
molecule.
c. Sucrose (table sugar) is a linkage of glucose to fructose.
d. Lactose (milk sugar) is a linkage of glucose and galactose.
8. Polysaccharides
a. Polysaccharides are chains of glucose molecules called polymers.
b. Most have the formula (C6H10O5)n where n is the number of simple sugar subunits.
c. Glycogen is a polymer of glucose; found in vertebrate liver and muscle cells, it is storage
carbohydrate of animals.
d. Cellulose is the principal structural carbohydrate of plants.
C. Lipids: Fuel Storage and Building Material (Figure 2.6)
1. Lipids are fats and fat-like substances.
2. Lipids have low polarity, therefore they are insoluble in water but soluble in organic solvents.
3. Neutral Fats
a. Stored fats are derived directly or converted from carbohydrates; they are the major animal
fuels.
b. Triglycerides consist of glycerol and three molecules of fatty acids.
c. Neutral fats are esters, combining alcohol and an acid.
d. Fatty acids in triglycerides are usually 14-24 carbons long.
e. When every carbon in a chain is bonded to two hydrogen atoms, it is saturated.
f. Unsaturated fatty acids, common in plant oils, have two or more carbon atoms joined by
double bonds. (Figure 2.7)
4. Phospholipids (Figure 2.8)
a. Phospholipids have a structural role in molecular organization of tissues and membranes.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
b.
2.3.
They resemble triglycerides with one fatty acid replaced by phosphoric acid and an organic
base.
c. Lecithin is an important phospholipid of nerve membranes.
d. The phosphate group is charged and therefore polar; the rest of the molecule is nonpolar, so
phospholipids can bridge both environments.
5. Steroids (Figure 2.9)
a. Steroids are complex alcohols with fat-like properties.
b. They are biologically important.
c. Steroids include cholesterol, vitamin D, adrenocortical hormones and sex hormones.
D. Amino Acids and Proteins (Figure 2.10)
1. Proteins are large molecules composed of 20 commonly occurring amino acids. (Figure 2.10)
2. Amino acids are joined by peptide bonds.
3. Two amino acids and a peptide bond form a dipeptide.
4. With one free amino group on one end and a free carboxyl on the other, additional amino acids
can be joined to form a long chain of enormous variety.
5. Levels of Protein Structure
a. Primary structure is the sequence of amino acids in the polypeptide chain.
b. Secondary structure comes from the bond angles of the sequence: alpha-helix and beta
sheets.
c. Bending and folding of secondary structures forms the tertiary structure, often stabilized by
disulfide, hydrogen, ionic and hydrophobic bonds.
d. Quaternary structure occurs when several polypeptide chains form subunits of a huge protein
molecule, as in hemoglobin.
6. Proteins form much of the framework of the cytoplasm and organelles.
7. Proteins function as enzymes to catalyze most reactions; cell biology can be studied as protein
biology. (Table 2.1; Figure 2.11)
E. Nucleic Acids
1. Nucleic acids are complex substances of high molecular weight.
2. Sequence of nitrogenous bases encodes genetic information for inheritance.
3. They store directions for synthesis of enzymes and other proteins.
4. They are the only molecules that can replicate themselves.
5. DNA is deoxyribonucleic acid.
6. RNA is ribonucleic acid.
7. Both DNA and RNA are polymers of repeated units called nucleotides, each containing a sugar, a
nitrogenous base and a phosphate group.
Chemical Evolution
A. Oparin-Haldane Hypothesis
1. Aleksander Oparin and J.B.S. Haldane independently proposed a hypothesis of chemical
evolution.
2. They proposed the early atmosphere consisted of simple compounds: water, carbon dioxide,
hydrogen gas, methane and ammonia, but lacked oxygen.
3. The compounds necessary for life are not synthesized outside cells nor are they stable in the
presence of oxygen.
4. Rock evidence indicates virtually no atmospheric oxygen at earliest times; this provides a reducing
atmosphere.
5. Both methane (CH4) and ammonia (NH3) are fully reduced compounds.
6. Such an atmosphere, with variations in heat and high radiation, was conducive to prebiotic
synthesis but unsuited to modern life forms.
7. Many chemicals would not react without a continuous source of free energy to produce a reaction.
8. Electrical discharges in lightning today produce a large amount of organic matter.
9. Alternative to the “hot dilute soup” scenario is the hydrothermal vent hypothesis that places these
extreme events underwater.
B. Prebiotic Synthesis of Small Organic Molecules (Figure 2.12)
1. In 1953, Stanley Miller and Harold Urey tested the Oparin-Haldane hypothesis.
2. The simple mixture, with time (a week), was 15% converted to organic compounds.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
3.
4.
5.
2.4.
Many compounds related to life were formed: amino acids, urea and fatty acids.
Critics contend that the early earth atmosphere may have been different from Miller’s test.
Omitting ammonia and methane resulted in smaller amounts of compounds and required longer
time periods.
6. More recent experiments have clarified the sequences leading through formaldehyde, hydrogen
cyanide, cyanoacetylene, etc. that react with water and ammonia or nitrogen to produce a wider
array of organic compounds.
C. Formation of Polymers
1. The next state required condensation of amino acids, nitrogenous bases and sugars.
2. Water tends to drive reactions toward decomposition by hydrolysis. (Box; Tables 2.2-2.5)
3. Need for Concentration
a. Violent early earth processes and weather provided ample opportunity for “organic scum.”
b. Surfaces of clay and iron molecules could have provided sites for concentration.
4. Thermal Condensations
a. Most biological polymerizations are condensation (dehydration) reactions.
b. In living systems, condensation reactions occur in wet environments with enzymes.
c. Without enzymes and ATP energy, macromolecules soon decompose.
d. Heating a mixture of amino acids yields many polypeptides without enzymes present.
e. Thermal synthesis of polypeptides forms proteinoid microspheres.
f. Microspheres contain outer walls that are double membranes with osmotic properties.
g. They are the size of bacteria, grow by accretion and bud similar to bacteria.
h. Formed under volcanic conditions, they may be precursors to life or chemical artifacts.
Origin of Living Systems
A. Self-replicating Systems (Figure 2.13)
1. Fossils date to 3.8 billion years ago; earliest life form probably originated 4 billion years ago.
2. Protocells would have been autonomous, membrane-bound units with functional organization that
permitted self-reproduction.
3. On top of previous chemical evolution, nucleic acids were needed as simple genetic systems.
4. This causes a biological paradox.
a. How could nucleic acids appear without the enzymes to synthesize them?
b. How could enzymes evolve without nucleic acids to direct their synthesis?
5. Their RNA, not protein content, catalyzes translation of mRNA by ribosomes.
6. Therefore, earliest enzymes could have been RNA, which would have been the earliest selfreplicating molecules; thus it would have been an “RNA world.”
7. Proteins are better catalysts and DNA is more stable; thus they would eventually be selected.
8. Before this stage, only environmental conditions and chemistry shaped biogenesis.
9. After this stage, the system responds to natural selection and evolves.
B. Origin of Metabolism (Figure 2.14)
1. History of the evolution of complex metabolism is yet to be understood; a model is proposed here.
2. Autotrophs synthesize their own food; heterotrophs must obtain food from the environment.
3. Earliest microorganisms are considered primary heterotrophs; they were probably anaerobic and
similar to Clostridium bacteria.
4. They could survive as long as the nutrient soup was abundant; protocells that converted inorganic
precursors to a required nutrient would have a selective advantage as nutrients were depleted.
5. Evolution of autotrophic organisms required gaining enzymes to catalyze conversion of inorganic
molecules to more complex ones.
C. Appearance of Photosynthesis and Oxidative Metabolism
1. Autotrophy evolves with photosynthesis.
2. Modern photosynthesis involves carbon dioxide and water to form sugar and oxygen.
3. Early photosynthesis probably used hydrogen sulfide or other hydrogen sources.
4. Production of oxygen began building an atmosphere; at 1% of its current level, oxygen begins to
form an ozone shield and restrict UV radiation reaching the surface.
5. Then photosynthetic organisms spread across land and water, increasing oxygen production.
6. Oxidative (aerobic) metabolism appeared using oxygen as the terminal receptor and completely
oxidizing glucose to carbon dioxide and water.
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Copyright © 2005 – The McGraw-Hill Companies srl
2.5.
7. Cyanobacteria, eukaryotic algae and plants have generated our current atmosphere of 21% oxygen.
Precambrian Life
A. Cambrian Explosion
1. Pre-Cambrian covers time before Cambrian began nearly 600 million years ago.
2. Most animal phyla appear within a few million years at the beginning of Cambrian: the
“Cambrian explosion.”
3. This likely represents the absence of fossilization rather than abrupt emergence.
B. Prokaryotes and the Age of Cyanobacteria (Blue-Green Algae)
1. Primitive Structures of Prokaryotes
a. A single DNA molecule, lacking histones, is in a nucleoid but not bound by nuclear
membranes.
b. They lack mitochondria, plastids, Golgi apparatus and endoplasmic reticulum.
c. During division, the nucleiod divides and replicates but does not go through organized
mitosis.
d. Cyanobacteria peaked one billion years ago; they were dominant for two-thirds of life’s
history.
2. They are placed in the kingdom Monera by many taxonomists, and in kingdom Eubacteria by
others.
3. Prokaryotes comprise two lineages of very distinct organisms.
a. Most bacteria are in the kingdom Eubacteria.
b. Archaebacteria have a unique cellular metabolism, different cell wall chemistry and unique
ribosomal RNA.
C. Appearance of the Eukaryotes
1. Advanced Structures of Eukaryotes
a. A membrane nucleus contains chromosomes composed of chromatin.
b. There is more DNA, and eukaryotic chromatin contains histones and RNA.
c. Cellular division usually is an organized process called mitosis.
d. In the cytoplasm are many membrane-bound organelles.
2. Fossils suggest eukaryotes arose 1.5 million years ago.
3. Lynn Margulis and others propose eukaryotes are a symbiosis of two or more bacteria.
a. Mitochondria and plastids contain their own DNA.
b. Nuclear, plastid and mitochondrial ribosomal RNAs show distinct evolutionary lineages.
c. Plastid and mitochondrial ribosomal DNA is closer to bacterial DNA.
d. Plastids are closest to cyanobacteria in structure and function.
e. A host cell that could incorporate plastids or mitochondria with their enzymatic abilities
would be at a great advantage.
4. Eukaryotes may have originated many times.
5. Heterotrophs that cropped cyanobacteria provided ecological space for other types of organisms.
6. Food chains of producers, herbivores and carnivores accompanied a burst of evolutionary activity
that may have been permitted by atmospheric changes.
7. The merging of disparate organisms to produce evolutionary novel forms is called symbiogenesis.
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Copyright © 2005 – The McGraw-Hill Companies srl
Lecture Enrichment
1.
2.
3.
4.
5.
6.
7.
Some substances have macroscopic images (e.g. sugar, lipids, protein in meat) and the large size of an albumin
molecule is apparent in the thick viscosity of egg white, but it is difficult to image something that is primarily
nucleic acid, etc. without lab work.
Note how different molecules such as nucleic acids and proteins may appear different in various life forms but
still have the same basic structure to perform the same kind of job. Why are some molecules essentially the
same in bacteria and humans and very different in others?
Draw, use transparencies, slides or video to illustrate the different isomeric forms of the hexose sugars glucose,
fructose, and galactose, and reasons for their different characteristics. Show how the structures fit into enzymes
and why different enzymes would be needed to interact with different isomers.
Speculate what would happen if genetic engineering gave humans the ability to directly digest cellulose. Would
this be useful or not? Ask students to consider the structure of our digestive tracts and the current use of
cellulose as roughage.
Describe how denaturation affects the different levels of a protein's structure. Which levels would be most
affected by denaturation? Contrast denaturation caused by heat (cooking food) as opposed to mild denaturation
caused by reversible pH changes.
Compare the bonds that link the carbohydrates, lipids, proteins and nucleic acids. Consider the size of the final
molecules and which ones are branched and unbranched. Prepare students for the link between the information
in DNA, RNA and proteins that will be discussed later.
Early researchers probing the possibility of life on other planets speculated that it might be based on another
atom besides carbon–perhaps silicon. Ask students to consider the chemical properties of silicon compared to
carbon and speculate on how this might make life different or impossible as we know it.
Commentary/Lesson Plan
Background: There is substantial chemical knowledge assumed in this chapter, including references to rather
remote properties of clay soil and microspheres. Most discussion of basic carbohydrates, lipids and proteins should
constitute review from previous biology coursework in high school and college.
Misconceptions: Students may assume that most major breakthroughs are made by the U.S. science establishment;
both J.B.S. Haldane (British) and Aleksander Oparin (Russian) were not Americans. How we view the world
determines what we believe and what we believe determines how we view the world; thus anti-evolutionists focus
on detecting contradictions and paradoxes in evolutionary theory, but the ribozyme/RNA world discovery
demonstrates how some logical dilemmas resolve themselves. Students often only relate “polymer” with plastic, but
the monomer-polymer concept for cellulose, chitin, etc. is equivalent. Many students will find it “intuitive” that the
first cells had to be autotrophic.
Schedule: The speed of coverage of this chapter will vary considerably depending on the general chemistry
background of students. Some understanding of basic chemistry is critical to appreciating the roles of organelles in
the next chapter.
HOUR 1 2.1.
2.2.
HOUR 2 2.3.
Spontaneous Generation of Life
A. History
Organic Molecular Structure of Living
Systems
A. Carbon
2.4.
B. Carbohydrates
C. Lipids
D. Amino Acids and Proteins
E. Nucleic Acids
2.5.
2.6.
Chemical Evolution
A. Oparin-Haldane Hypothesis
B. Prebiotic Synthesis of Small
Organic Molecules
C. Formation of Polymers
Origin of Living Systems
A. Self-replicating Systems
B. Origin of Metabolism
C. Appearance of Photosynthesis and
Oxidative Metabolism
Precambrian Life
A. Cambrian Explosion
B. Prokaryotes and the Age of
Cyanobacteria (Blue-Green Algae)
C. Appearance of the Eukaryotes
A. Symbiogenesis
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Copyright © 2005 – The McGraw-Hill Companies srl
ADVANCED CLASS QUESTIONS:
1. The atoms and bonds within a molecule determine its chemical and physical properties. Compare fats that
contain mostly saturated fatty acids with oils that contain mostly unsaturated fatty acids to demonstrate this
concept.
2. The properties of a molecule determine the role that the molecule plays in the cells or the body of an organism.
Why are phospholipids useful in membranes?
3. Ask why life is based on carbon. Note the characteristics of carbon that could be responsible for this usage.
Ask students to speculate why silicon, with four electrons in its outer shell, would function as the basis of life.
4. Query how the amount of ATP used in one day can exceed by many times the amount of ATP in the human
body.
5. Ask if condensation and hydrolysis reactions would be exact opposites of each other. Point out that these
reactions are not generally one-step processes, but require several steps and several enzymes to carry out the
complete reaction.
6. Discovery of liquid water under the frozen surface of a distant moon in our solar system has caused scientists to
speculate on the possibility of life on that moon. Researchers hold little hope of any familiar life form existing
on any planet or moon in the absence of water. Why?
7. Life has a chemical and physical basis. Give an example from your knowledge of nutrition, medicine or the
environment to show that this concept has everyday applications.
8. Atomic structure involves electronic energy levels. Show that living things are dependent upon the energy
relationships of electrons.
9. So far, for every molecule that life forms can put together, such as cellulose or chitin, there are bacteria that can
digest them into sugar and other smaller molecules. What would happen if a tree or insect could build a
complex molecule that no organism or natural process could decompose?
10. Many insects feed exclusively on one type of food such as plant sap (primarily sugar), blood proteins or starch.
Yet these organisms are themselves made of a wide range of molecules. Where does this molecular diversity
come from?
Twelfth Edition Changes:
1.
There are no sigficant changes in this chapter.
There is a more complete discussion of symbiogenesis (this is a modification of the original term,
endosymbiosis).
13
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Copyright © 2005 – The McGraw-Hill Companies srl
Source Materials
[Bold = recommended; for vendor abbreviations, see list of distributors in Appendix 1.]
Acids and Bases (FH), 14-min. video
Acids and Bases (PLP), Apple, MS-DOS
All About Acids and Bases (CBSC), 65-min. filmstrip (498731V)
All About Science II (Q), Mac, MS-DOS CD
The Atom (CAM), Mac, MS-DOS
The Atom (HH), 36-min. video
The Atom that Makes a Difference [Carbon] (FH), 26-min. video
Atoms to Anatomy (VDISC) laserdisc
Atoms and Elements (PLP), Apple, MS-DOS
Basic Biochemistry of Life (CBSC), Mac, Win, MS-DOS CD
Basic Chemistry for Biology Students (HRM) (IM) 21-min. video
Beaker (CAM), Mac, MS-DOS
Biochemistry (IM) (SK&BL) Mac, Win, MS-DOS CD
Biochemistry: Chemistry of Living Things (EDVO), MS-DOS and Mac CD
Biochemistry of the Immune System (CAM), Apple, Mac, MS-DOS
Chemaid (CSG), Mac
Chemical Bond and Atomic Structure (PHO), 16-min. video
Chemistry of Carbohydrates, The (ei), video
Chemistry of Life (CBSC), 24-min. video
Chemistry of Proteins, The (ei), video
Cycles of Life: Exploring Biology–Chemical Foundations of Life (A-CPB), 30-min. video
Desktop Molecular Modeler, Schools Version (OX), MS-DOS CD
DNA/RNA Builder (STAT), Mac
DTMM Structure Library: Biochemistry (OX), MS-DOS CD
DTMM Structure Library: Organic Chemistry (OX), MS-DOS CD
DTMM Structure Library: Pharmacology (OX), MS-DOS CD
DTMM Structure Library: Biomacromolecules (OX), MS-DOS CD
Functional Chemistry in Living Cells (PLP), 60-min. video
Living Cells (AIMS), Mac, Win CD-ROM, 19-min. video, laserdisc
Molecular Biology (CAM), Win, Mac CD
Molecular Recognition (PHO), 36-min. video
The Molecular Building Blocks of Life (PLP), 13-min. video
Molecular Structures in Biology (OX), MS-DOS CD
Molecules (STAT), Mac
NOVA: The Shape of Things (MBI) (WGBH), 60-min. video
NOVA: The Universe Within (MBI) (WGBH), 90-min. video
Nucleic Acids (PLP), MS-DOS
Organic Reaction Mechanisms (CAM), Mac, MS-DOS
Oxygen: What a Gas! (HRM), 29-min. video
Proteins: Structure and Function and The Genetic Code (JLM), 60-min. video
The World of Chemistry–Carbon (A-CPB), 30-min. video
The World of Chemistry–Proteins: Structure and Function (A-CPB), 30-min. video
The World of Chemistry–Water (A-CPB), 30-min. video
14
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
CHAPTER
3
CELLS AS UNITS OF LIFE
CHAPTER OUTLINE
3.1.
3.2.
Cell Concept
A. History
1. English scientist Robert Hooke described “little boxes of cells” in 1663 using a compound
microscope.
2. Dutch microscopist Anton van Leeuwenhoek made extensive observations and reported them in
letters to Royal Society of London.
3. Advanced high-quality lenses in the early 19th century made it possible to examine cells.
B. Cell Theory
1. The cell theory asserts that all living organisms are composed of cells.
2. In 1838, Matthias Schleiden announced plant tissue was made of cells.
3. In 1839, Theodore Schwann concluded animals were made of cells.
4. In 1840, J. Purkinje described cell contents as protoplasm; modern understanding of cell
organelles makes “cytoplasm” the preferred term.
5. In 1858, another Germna, Rudolf Virchow, recognized that all cells came from pre-existing cells.
C. How Cells Are Studied (Figures 3.1, 3.2)
1. Light microscopes use light rays; they are limited in magnification and resolution.
2. The transmission electron microscope (TEM) uses electrons passing through the specimen.
a. The wavelength of the electron is 0.00001 that of light, allowing greater magnification.
b. Specimens must be prepared in thin section; the electrons pass through to a photographic
plate.
3. Scanning electron microscope (SEM) scans electrons across a metal-coated specimen; it has a
lower magnification than TEM.
4. X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy may reveal the shape
of molecules.
5. Cytology, the study of cells, has its own methods. (Figure 3.3)
a. Cells are disrupted in a blender and separated by a centrifuge; organelles are then recovered.
b. Use of radioisotopes allow for tracing of metabolic pathways.
c. Proteins are extracted and purified; antibodies prepared against the protein can be combined
with fluorescent substances to detect the location of the protein.
Cell Organization: Complex Organelles and Energy Transformations
A. Prokaryotic and Eukaryotic Cells (Table 3.1)
1. Prokaryotes lack a membrane-bound nucleus found in eukaryotes.
2. However, both have DNA, use the same genetic code, synthesize proteins and use ATP.
B. Major Components of Eukaryotic Cells and Their Functions
1. The cell membrane is the outermost membrane and regulates the entrance and exit of molecules.
2. A double membrane that separates the nucleus from cytoplasm encloses the nucleus.
3. Plant cells usually contain plastids for photosynthesis and have a cellulose-based cell wall.
C. Cell Membrane (Figures 3.4, 3.5, 3.6)
1. The current model of membrane structure is the fluid-mosaic model.
2. The cell membrane is phospholipid bilayer in which protein molecules are partially or wholly
embedded.
3. The phospholipid molecules have their water-soluble ends toward the outsides and fat-soluble
portions toward the inside of the membrane.
4. The layer is liquid, providing flexibility; embedded cholesterols decrease this fluidity.
5. Glycoproteins are proteins with carbohydrates attached.
6. Some proteins catalyze transport of substances such as ions across the membrane.
7. Others are receptors for specific molecules.
D. Nucleus (Figure 3.7)
1. Nuclear envelopes contain less cholesterol than cell membranes; pores allow relatively large
molecules to readily move through.
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Chromatin is a threadlike material that coils into chromosomes just before cell division occurs; it
contains DNA, protein histones and nonhistone proteins.
3. Nucleoli are dark-staining spherical bodies in nucleus and synthesize ribosomal RNA.
4. After transcription from DNA, ribosomal RNA joins proteins to form ribosomes.
5. The outer membrane of nucleus is continuous with endoplasmic reticulum.
E. Endoplasmic reticulum (Figure 3.8)
1. The endoplasmic reticulum (ER) is a system of membrane channels continuous with outer
membrane of the nuclear envelope.
2. The space between membranes of nuclear envelope communicates with channels (cisternae) in
ER.
3. The rough ER is studded with ribosomes on cytoplasm side; products enter cisternae for transport
to the Golgi apparatus. (Figures 3.9, 3.10)
4. Ribosomes on the rough ER synthesize peptides or proteins that enter the ER cisternae or
membrane.
5. Some ribosome produces are destined for incorporation into the cell membrane or for export from
the cell.
6. The smooth ER functions to synthesize lipids and phospholipids.
F. Lysosomes
1. Lysosomes are membrane-bound vesicles produced by the Golgi complex.
2. Lysosomes contain digestive enzymes.
3. These enzymes help digest foreign material or engulfed bacteria: lysosome vesicles pour enzymes
into a food vacuole or phagosome.
4. They destroy injured or diseased cells; a healthy cell must maintain the membrane.
G. Contractile vacuoles contain fluid and regulate ions and water.
H. Mitochondria are present in nearly all eukaryotic cells. (Figure 3.11)
1. Mitochondria are bound by a double membrane; inner membrane folds (cristae) project into the
inner space (matrix).
2. Enzymes on the cristae break down carbohydrate-derived products; ATP production occurs here.
3. Mitochondria are self-replicating; their own DNA specifies some proteins; nuclear DNA codes
other proteins.
I. Cytoskeleton (Figures 3.12, 3.13)
1. The cytoskeleton is a network of filaments and tubules that maintain support and form.
2. In many cells, they provide locomotion and translocation of organelles.
3. Microfilaments are thin, linear structures first recognized in muscle cells.
4. Actin filaments are long, thin protein fibers that act with several dozen other proteins.
5. One of these is myosin; the interaction causes contraction in muscle and other cells.
6. Microtubules are composed of the protein tubulin; they move chromosomes during cell division.
7. Microtubules radiate out from a microtubule organizing center: a centrosome.
8. Centrosomes are not membrane bound. (Figure 3.14)
9. Centrioles are short cylinders with 9 triplets of microtubules; centrosomes contain two centrioles
lying at right angles to each other.
10. Intermediate filaments are larger than microfilaments and smaller than microtubules in size.
J. Surfaces of Cells and Their Specializations
1. Free surfaces of epithelial cells of tubes and cavities sometimes bear cilia or flagella.
a. Single celled organisms may use cilia or flagella to propel forward.
b. Flagella provide locomotion for male reproductive cells (sperm).
c. Locomotory cilia and flagella both have a cylinder of nine pairs of microtubules encircling
two single microtubules (9 + 2 pattern of microtubules).
d. At the base of each cilium or flagellum is a basal body (kinetosome).
2. Ameboid movement uses pseudopodia.
a. Ameboid movement is seen in embryonic cells, white blood cells and protozoa.
b. Cytoplasmic streaming utilizes actin microfilaments to extend pseudopodia.
c. Some specialized pseudopodia have cores of microtubules that assemble and dissemble.
3. Cell Junctions (Figure 3.15)
2.
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Copyright © 2005 – The McGraw-Hill Companies srl
In tight junctions, cell membrane proteins fuse to each other; they hold cells together so
tightly that tissues (e.g., epithelial lining of stomach) form barriers.
b. Desmosomes are “spot welds”; firmly attached to the cytoskeleton within each cell, are joined
by intermediate filaments, and hold cells together with linker proteins to increase the strength
of tissues in the heart, stomach and bladder.
c. Gap junctions allow cells to communicate; tiny canals between cells allow the cytoplasm to
be continuous in epithelial, nervous and muscle tissues.
d. Some cell surfaces are laced together with membranes infolding like a zipper (e.g. epithelia of
kidney tubules).
4. Microvilli are small finger-like projections of cell membranes such as those that line the intestine;
also called brush borders, they increase absorptive area. (Figure 3.16)
Membrane Function
A. Plasma Membrane; Dynamic and Selective
1. Also called the plasmalemma, it maintains cellular integrity.
2. It separates the interior environment from the exterior and regulates molecule traffic flow.
3. It provides many unique functional properties of specialized cells.
4. Internal membranes divide a cell into compartments; they are sites for most enzymatic reactions.
B. Cell Membrane Function
1. The membrane is the gatekeeper to substances that enter and exit a cell.
2. Because the interior and exterior are different, the membrane is a critical controller.
3. Three principle methods are used for crossing a cell membrane:
a. Diffusion along a concentration gradient,
b. Substances bind to a site in a mediated transport system, and
c. Endocytosis encloses a particle in a vesicle that is engulfed.
4. Diffusion and Osmosis (Figure 3.17)
a. Diffusion is movement of particles from higher to lower concentration, or along a
concentration gradient.
b. If a membrane is permeable to a solute, diffusion will continue until concentrations are equal.
c. Most membranes are selectively permeable, only allowing some molecules to pass.
d. Most membranes allow free passage of water, gases, urea, and lipid-soluble solutes.
e. Water-soluble molecules (e.g. sugar), electrolytes and some macromolecules move across by
carrier-mediated processes.
f. Osmosis is movement of water molecules down a concentration gradient across a membrane.
g. A salt solution in a cell will cause diffusion of water inward until the increase in weight
(hydrostatic or osmotic pressure) of the solution causes it to be in equilibrium.
h. Osmotic potential is a term used to avoid confusion of term “osmotic pressure” in the absence
of membrane and pure water reference.
i. Marine fish have one-third the solute concentration as seawater; they are hyposmotic to
seawater.
j. A marine fish swimming up a river delta would pass through a region where external and
internal solutes were equal or isosmotic.
k. In freshwater, its blood solutes would be hyperosmotic to the freshwater.
5. Mediated Transport (Figure 3.18)
a. Special proteins (transporters or permeases) move nutrients and wastes across the
membrane.
b. Permeases form a small passageway for very specific solute molecules.
c. When all transporters become saturated with solutes, the rate of influx does not increase with
more solute; this measures the amount of transporter molecules.
d. With simple diffusion, the greater the difference in solute concentrations, the higher the flux.
e. Two mediated transport mechanisms are recognized.
1) Facilitated diffusion permeases assist a molecule (e.g. sugar) to diffuse that otherwise
cannot. (Figure 3.19)
2) Active transport uses energy to transport molecules against the concentration gradient.
f. Most animal cells require internal potassium levels 20–50 times outside levels; outside
sodium levels may be ten times inside levels.
a.
3.3.
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Copyright © 2005 – The McGraw-Hill Companies srl
g. In many cells, sodium and potassium pumping are linked using the same transporter molecule.
Endocytosis (Figure 3.20)
a. All processes (phagocytosis, potocytosis and receptor-mediated endocytosis) require energy.
b. Phagocytosis is common among protozoa and lower metazoa.
1) An area of cell membrane coated internally with actin-and-myosin forms a pocket to
engulf material.
2) The membrane-enclosed vesicle detaches from the cell surface for internal digestion.
c. Potocytosis
1) Small areas of surface membrane invaginate into tiny vesicles called caveolae.
2) Specific binding receptors for the molecule or ion are on this cell surface.
3) It is involved in taking in some vitamins, hormones and growth factors.
d. Receptor-mediated endocytosis
1) Plasma membrane proteins bind specific particles called ligands.
2) This occurs in clathrin-coated pits coated with receptors.
3) Brought within the cell, the pit is uncoated and the ligand disassociated to be recycled.
4) Some proteins and peptide hormones are brought into cells by this method.
7. Exocytosis
a. This is the reverse of the invagination and formation of a vesicle.
b. It removes indigestible residues, secretes hormones and transport substances.
Mitosis and Cell Division
A. Cell Types
1. All cells in nearly all multicellular organisms originated from division of a single cell, the zygote.
2. A zygote is formed from union of egg and sperm, the gametes.
3. Formation of body (somatic) cells by nuclear division is mitosis.
4. Mitosis delivers chromosomes and their DNA to the cell lineage.
5. Although the cell lineage differentiates, the genes not expressed are still present.
6. Mitosis ensures the equality of genetic material.
7. In animals that reproduce asexually, mitosis transfers genetic information to progeny.
8. In animals that reproduce sexually, parents produce sex cells (known as gametes or germ cells)
with half the number of chromosomes.
a. This prevents the union of gametes from doubling the number of parental chromosomes.
b. This requires reduction division or meiosis.
B. Chromosome Structure
1. Chromatin
a. Eukaryotic DNA is in the form of chromatin when a cell is not dividing.
b. Chromatin is a complex of DNA with histone and nonhistone proteins.
2. Chromosomes
a. Chromosomes stain deeply with biological dyes.
b. They are of set but varied lengths.
c. A species will have a specific number of chromosomes in all cells except gametes.
d. Chromosomes are shortened chromatin; they are constricted at the centromere, which is the
location of the kinetochore.
e. DNA must be packaged so it is accessible during transcription.
C. Phases in Mitosis
1. Cell division involves division of nuclear chromosomes (mitosis) and cytoplasm (cytokinesis).
a. When a nucleus divides without cytokinesis, a multinucleate cell results.
b. When several cells fuse, it can also form a multinucleate syncytium.
2. Mitosis is a four-step process with each step merging into the next.
3. When the cell is not actively dividing, it is in interphase during which DNA replicates and genes
are transcribed.
4. Prophase (Figures 3.21-3.23)
a. In early prophase, centrosomes replicate and the two centrosomes migrate to opposite sides of
the nucleus.
b. Microtubules form a football-shaped spindle between the centrosomes.
c. Other microtubules radiate outward to form asters.
6.
3.4.
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d.
Nuclear chromatin condenses into chromosomes; the sister chromatids were actually formed
during interphase.
e. Spindle fibers reach the centrosome and bind to the kinetochore.
5. Metaphase (Figure 3.24)
a. Kinetochore fibers pull condensed sister chromatids to the central metaphasic plate.
b. Centromeres line up precisely on the equatorial plate; arms of chromatids dangle.
6. Anaphase
a. A single centromere that holds the chromatids together now splits.
b. Chromosomes move toward their respective poles, pulled by kinetochore fibers.
c. At the end of anaphase A, microtubules shorten by disassembly of tubulin units at the
kinetochore end.
d. In anaphase B, chromosomes approach respective centrosomes as the spindle lengthens.
e. Tubulin in microtubules intermingles and pushes the ends of the spindle apart.
7. Telophase
a. Phase begins as daughter chromosomes reach each pole.
b. Spindle fibers disappear.
c. Chromosomes lose identity and diffuse into chromatin network in nucleus.
d. Nuclear membranes re-form in daughter cells.
D. Cytokinesis: Cytoplasmic Division
1. During the final stage of nuclear division, a cleavage furrow appears on cell surface.
2. Microfilaments of actin just beneath the surface draw the furrow inward.
3. Infolding edges of cytoskeleton meet and fuse, completing cell division.
E. Cell Cycle (Figure 3.25)
1. Cells undergo cycles of growth and replication.
2. A cell cycle is a mitosis-to-mitosis cycle, the interval between one cell generation and the next.
3. Interphase
a. Nuclear division occupies 5-10% of the cell cycle; the rest is interphase.
b. Early concepts of interphase as an inactive stage of rest are incorrect.
c. DNA replication occurs during interphase.
d. S (for synthesis) stage lasts about 6 of the 18-24 hours of a cell cycle in a human.
e. Both strands of DNA replicate a complimentary strand.
f. The G1 period precedes the S stage; transfer RNA, ribosomes, messenger RNA and enzymes
are synthesized.
g. The G2 period follows the S stage; spindle and aster proteins form in preparation for
chromosome separation.
4. Embryonic Cells
a. Embryonic cells divide rapidly with no cell growth between divisions, just subdivision.
b. DNA synthesis may be hundreds of times faster in embryonic cells than in adult cells.
5. As organisms develop, the cell cycle of most cells lengthens.
a. A nonproliferative phase or G0 ends the cycle.
b. Neurons do not divide further after birth and are in a permanent G0.
6. Cell Cycle Control (Figure 3.26)
a. Regulation of the cell cycle is mediated by cyclin-dependent kinases (cdk’s).
b. Cyclins are activating subunits of cdk’s.
c. Kinase enzymes add phosphate groups to other proteins to activate or inactivate them.
7. Flux of Cells
a. Cell division is very rapid during early development of an organism.
b. The human infant has 2 trillion cells that originated from one fertilized egg; this represents 42
cell divisions.
c. Five more cell divisions produce an adult with 60 trillion cells.
d. Various cells divide in days, months or years: muscle and nerve cells stop dividing in
childhood or before.
e. A human sheds about 1-2% of the total number of cells daily from skin, digestive tract, sperm
and short-lived red blood cells.
8. Apoptosis
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a.
b.
c.
Apoptosis is programmed cell death.
Apoptosis is necessary for normal development and suicide of unhealthy cells.
Cells shrink, fragment, and then the remains are taken up by surrounding cells.
Lecture Enrichment
1.
2.
3.
4.
5.
6.
7.
8.
The ability of early microscopists to see cell structures is amazing. Slides or overhead transparencies of
Leeuwenhoek’s primitive single lens device, each made to accommodate another view, help illustrate the
difficulty of working with primitive instruments. The Golgi apparatus was at the limit of light microcopy
resolution and is a tribute to his microscopic ability, as was his neuron preparations. Ask students to consider
how research had to await better microscope technology and different staining methods to allow smaller
structures to be examined.
Clarify the difference between magnification (making something appear larger) and resolution (distinguishing
between two adjacent structures).
Show scanning electron micrographs of a freeze fractured plasma membrane. Ask students to determine which
face is the cytoplasmic and which the external side of the membrane; proteins are more frequent in the
cytoplasmic face. Ask why that would be so.
Most students have seen an oil slick on a water puddle. If we measure the volume of oil, measuring the surface
area of the slick and dividing this into the volume determines the molecular size. With this information, ask
students how they could show that the cell membrane lipid bilayer is a two-layer fluid.
While it is a congealed colloidal mass rather than a lipid bilayer, hot chocolate scum can be used as an example
of a “membrane” that forms from natural physical laws without any vitalistic forces.
The term “cholesterol” has a generally bad connotation. Describe the function of cholesterol in the plasma
membranes of animal cells, and ask why it is missing in plant cells. There are other lipids that serve the same
function in plant membranes.
The immense diversity of proteins that are embedded in or attached to the plasma membrane have a wide array
of different functions in the animal kingdom, and determine cell and tissue “identity.” Ask why these
membrane-associated proteins are also found in membrane-bound organelles such as vesicles, vacuoles and
mitochondria. Compare how they function there with their function in the plasma membrane.
At the start of class, place dialysis bags containing various molar solutions of saline in beakers of differing
molar solutions. Examine at the end of class and determine which beakers represent a cell in hypotonic,
hypertonic, or isotonic solutions.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Commentary/Lesson Plan
Background: Most students have some experience working with a microscope, although the movement toward
using a microscope-mounted television camera to demonstrate slides may remove this critical experience from
students’ hands. Providing microscopic or photographic images is critical for students to visualize most cell
components. This chapter is also heavily laden with cell structure terminology and chemical concepts that may not
be in all students’ backgrounds. Visuals and demonstrations are critical to understanding most membrane
properties. Clear examples of hypotonic, hypertonic, and isotonic solutions–explained in relationship to the external
solution–are critical even for biology students with previous exposure.
Misconceptions: Students may have many mistaken beliefs relative to this section: Cellular life is too complex to
be explained by laws of physics and chemistry. Genetic coding for all cell structures is only in the nuclear DNA.
Cholesterol is always bad. No reproductive cell processes are occurring during interphase. Stages of mitosis are
distinct or noncontinuous and jerkily move from one stage to another. We must keep all the cells we produce; cell
loss is bad. Life is always good. Death is always bad.
Schedule:
HOUR 1 3.1.
3.2.
HOUR 2 3.3.
Cell Concept
A. History
B. Cell Theory
C. Cells Are Studied
HOUR 3 3.4.
Cell Organization:
Complex Organelles and Energy
Transformations
A. Prokaryotic and Eukaryotic Cells
B. Major Components of Eukaryotic
Cells and Their Functions
C. Cell Membrane
D. Nucleus
E. Endoplasmic reticulum
F. Lysosomes
G. Contractile Vacuoles
H. Mitochondria
I. Cytoskeleton
J. Surfaces of Cells and Their
Specializations
Membrane Function
A. Plasma Membrane; Dynamic and
Selective
B. Cell Membrane Function
Mitosis and Cell Division
A. Cells Types
B. Chromosome Structure
C. Phases in Mitosis
D. Cytokinesis: Cytoplasmic Division
E. Cell Cycle
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
ADVANCED CLASS QUESTIONS:
1. "Vitalism" is the mistaken belief that additional vital forces beyond the normal laws of chemistry and physics
are necessary to explain life and movement inside cells. Why are modern biologists not vitalists?
2. Why are syncitial and multinucleate tissues not a violation of the cell theory?
3. Why does the electron microscope have greater resolving power than the light microscope?
4. Plants have rigid walls; thus freezing and thawing of vegetables destroys these structures as small sharp ice
crystals pierce them. While meat lacks cell walls and we do not notice additional “limpness” after repeated
thawing, it still produces the bad taste of "freezer burn." What organelle is involved in this autodigestion? How
would this concept affect the plans of individuals who schedule themselves to be frozen immediately after death
in hopes of being thawed out and cured at some future date?
5. Life begins at the cellular level of organization. Which organelles contribute to the ability of the cell to
maintain its structure and grow? What are the functions of these organelles?
6. Why are sugar residues of glycoproteins and glycolipids located only on the outside face of the plasma
membrane? How are these residues important in cellular recognition?
7. Ask a student to trace the pathway a protein molecule takes through the endomembrane system from its
production on the rough ER to release from a vesicle at the cell's surface. Would the pathway be different if the
protein were made on a free ribosome?
8. Compare the functions of the different kinds of junctions that hold cells together and what kinds of cells they
would be likely to link.
9. You can "peel" a raw egg without breaking the membrane. If you place the shell-less egg in a glass of water, it
will swell to the size of an orange. Why is the flow one-way?
Twelfth Edition Changes: There are minor informational changes in this chapter and a number of new
or upgraded figures:
1.
2.
This is additional information concerning Rudolf Virchow, intermediate membrane-bound structures,
ribosomal structure and the fate of peptide production, as well as modest changes concerning cell cycle and
cell division.
There is a new diagram (Figure 3.6) of the cell membrane; a new diagram of the endomembrane system
(Figure 3.10); a new diagram of types of cellular communication (Figure 3.15); a new diagram of
endocytosis (Figure 3.20); a new diagram of mitosis (Figure 3.21); and new micrographs of the cell cycle
(Figure 3.24).
22
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Source Materials
[Bold = recommended; for vendor abbreviations, see list of distributors Appendix 1.]
Active Transport (FH), 15-min. video
The Architecture of Cells (IM), 45-min. video
The Architecture of Cells: Special Structure, Special Function (HRM) 51-min. video
Basic Biochemistry of Life (CBSC), Mac, MS-DOS CD
Building in Cells (Biology: Form and Function) (CPB), 24-min. video
The Cell (HH), 14-min. video
Cell Biology (PHO), 17-min. video
Cell Biology Vol. I-II (VDISC) laserdisc
Cell Biology (CBSC), Mac, MS-DOS CD
Cell Biology (SK&BL), Mac, Win, MS-DOS CD
The Cell: A Functioning Structure (Parts 1 and 2) (CRM), 30-min. video
Cell: A Functioning Structure (Parts 1 and 2) (CRM), 30-min. video
Cell: Its Structure (CBSC), filmstrip
Cell Motility and Microtubules (FH), 30-min. video
Cell Structure and Function (CBSC) (ei), slides
Cell Structure and Function (PLP) (SK&BL), Mac, Win, MS-DOS
Cell Structure and Function (CYBER) (EDVO), Mac, MS-DOS CD
Complete Living Cell Program (SK&BL) 6 15-min. videos
Cells (INT), Mac
Cells of Animals: Structure and Function (PLP), 25-min. video
Cells & Genes (MONA) Mac, MS-DOS CD
Cells and Life (SK&BL) 17-min. video
Cycles of Life: Exploring Biology–Secrets of the Cell (A-CPB), 30-min. video
Cytology and Histology (IM), 25-min. video
The Cytoplasm (PHO) (SK&BL), 15-min. video
Diffusion (IM), 29-min. video
Discovering the Cell (IM) (NGS), 28-min. video
Electron Microscopy (FH), 15-min. video
Exploring Cell Processes (SK&BL) Mac, Win CD
Functional Chemistry in Living Cells (IM) (PLP), 60-min. video
The Importance of the Nucleus (BSCS Classic Inquiry) (MDA), videodisc
Inside the Cell: Microstructures, Mechanisms and Molecules (GA), 44-min. video
Inside the Cell: Microstructures, Mechanisms, and Molecules (GA), slides
Introduction to Cell Structure: Part I, The Structure of the Cell (IM), 17-min. video
Introduction to Cell Structure (FISH), 2 24-min. videos
Introduction to Living Cells (PLP), 18-min. video
An Introduction to the Living Cell (CBSC), 30-min. video
Introduction to Cell Structure: Part I: The Structure of the Cell (IM), 17-min. video
Inside the Living Cell Photo CD (SK&BL) Mac, Win CD
Isolation and Metabolism of Mitochondria (FH), 15-min. video
Learning All About Cells and Biology (Q), Mac or MS-DOS CD
Learning More About Cells (Q), Mac or MS-DOS CD-ROM
Little Feet: Cilia and Flagella, Part I and II (IM), 22 and 35-min. video
The Living Cell (PHO), 15-min. video
Living Cells (AIMS), 14-min. laser videodisc
Membrane Potential Problem Solver (PLP) (TS), MS-DOS
Organelles and Origins (Biology: Form and Function) (CPB), 24-min. video
Osmosis and Diffusion (PLP), Mac, MS-DOS
Osmosis Lab (CAM) (EME), Apple, Mac, Win, MS-DOS CD
The Outer Envelope (PLP), 17-min. video
Plant and Animal Cells (CBSC), Apple
The Plasma Membrane (CAM) (EME), Apple, Mac, Win, MS-DOS CD
The Plasma Membrane (IM) (SK&BL), 15-min. video
Membrane Potential Problem Solver (PLP) (TS), MS-DOS
23
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Membranes (ei), video
The New Cell (IM), 40-min. video
The New Cell (ei), filmstrip
The Nucleus (PHO), 13-min. video
Osmosis and Diffusion (PLP), Mac, MS-DOS
Osmosis Lab (CAM) (EME), Apple, Mac, MS-DOS
pH, Osmosis, and Diffusion (ei), filmstrip
Plasma Membrane, The (PHO), 13-min. video
The Structure of the Cell: Part I (PLP), 20-min. video
The Study of the Cell (PLP), MS-DOS
Water and Ion Movement across Frog Skin (INT), Mac
Visualizing Cell Processes Series (CBSC) (SK&BL), 5 12-min. videos or laserdisc
24
CHAPTER
4
ORGANIC EVOLUTION
CHAPTER OUTLINE
4.1.
Origins of Darwinian Evolutionary Theory
A. Pre-Darwinian Evolutionary Ideas
1. Before the 18th century, speculation on origin of species was not scientific.
2. Creation myths portrayed a constant world after a creation event.
3. Early Greek philosophers considered some ideas of evolutionary change.
a. Xenophanes, Empedocles and Aristotle developed early ideas about evolution.
b. Fossils were recognized as former life destroyed by natural catastrophe.
c. Lacking a full evolutionary concept, the idea faded before the rise of Christianity.
4. Biblical account of creation became a tenet of faith.
a. Evolutionary views were heretical.
b. Archbishop Ussher calculated 4004 BC as date of life’s creation.
5. French naturalist Georges Luis Buffon suggested that environment modified animal types; set age
of earth at 70,000 years.
6. French biologist Jean Baptiste de Lamarck offered first complete explanation in 1809.
a. He convincingly argued that fossils were remains of extinct animals.
b. Lamarck’s mechanism was inheritance of acquired characteristics.
c. He explained long necks of giraffes to stretching efforts of ancestral giraffes.
d. Lamarck’s concept is transformational; individuals transform their own traits to evolve.
e. In contrast, Darwin’s theory is variational or due to differential survival among offspring.
7. Geologist Sir Charles Lyell established the principle of uniformitarianism.
a. Uniformitarianism consists of two important principles:
1) Laws of physics and chemistry remain the same throughout earth’s history.
2) Past geological events occurred by natural processes similar to those observed today.
b. Natural forces acting over long periods could explain formation of fossil-bearing rocks.
c. Earth’s age must be measured in millions of years.
d. Geological changes are natural and without direction; both concepts underpinned Darwin.
B. Darwin’s Great Voyage of Discovery (1831-1836)
1. In 1831, Charles Darwin (almost 23) sailed aboard the small survey ship HMS Beagle.
2. Darwin made extensive observations in the five-year voyage.
a. Darwin collected the fauna and flora of South America and adjacent regions.
b. He unearthed long extinct fossils and associated fossils of South and North America.
c. He saw fossil seashells embedded in the Andes rocks at 13,000 feet altitude.
d. Observing earthquakes and severe erosion confirmed his views of geological ages.
3. The Galápagos Islands provided unique observations.
a. These volcanic islands are on the equator 600 miles west of Ecuador.
b. Galápagos means “tortoise”; the giant reptiles were exploited for food.
c. Each island varied in tortoises, iguanas, mockingbirds and ground finches.
d. The islands had similar climate but varied vegetation.
e. Island species therefore originated from South America and were modified under the varying
conditions of different islands.
f. He wrote that these unique animals and plants were the “origin of all my views.”
4. Darwin conducted the remainder of his work at home in England.
a. His collections and notebooks had been sent back before his return in October 2, 1836.
b. His popular travel journal, The Voyage of the Beagle, was published three years later.
c. In 1838, Darwin read an essay on population by Thomas R. Malthus.
d. Having studied artificial selection, a “struggle for existence” because of overpopulation gave
him a mechanism for evolution of wild species by natural selection.
e. He presented his ideas in a paper in 1844 and began work on a larger volume in 1856.
f. In 1858, he received a manuscript from a young naturalist, Alfred Russel Wallace,
summarizing the main points of natural selection.
g.
4.2.
Geologist Lyell and botanist Hooker persuaded Darwin to publish a paper jointly with
Wallace’s paper.
h. Darwin then rushed to publish a shorter “abstract” version in 1859: On the Origin of Species
by Means of Natural Selection.
i. 1250 copies sold of first printing in one day.
j. Darwin wrote a series of important additional books in the next 23 years.
Darwinian Evolutionary Theory: The Evidence
A. Perpetual Change
1. The living world is constantly changing in form and diversity.
2. Change in animal life is directly seen in the 600-700 million-year animal fossil history.
3. A fossil is a remnant of past life.
a. Insects in amber and frozen mammoths are actual remains.
b. Teeth and bones can petrify or become infiltrated with silica and other minerals.
c. Molds, casts, impressions and fossil excrement are also fossils.
4. Most organisms leave no fossils; the record is always incomplete and requires interpretation.
5. Interpreting the Fossil Record
a. The fossil record is biased because preservation is selective.
b. Vertebrate skeletons and invertebrates with shells provide more records.
c. Soft-bodied animals leave fossils only in exceptional conditions such as the Burgess Shale.
d. Fine fossil sites also include South Australia, Rancho La Brea, the Olduvai Gorge of Tanzania
and dinosaur beds in Alberta, Canada and Utah.
e. Fossils occur in stratified layers; new deposits are on top of older material.
f. “Index” or “guide” fossils are “indicators” of specific geological periods.
g. Layers often tilt and crack, and can erode or be covered with new deposits.
h. Under heat and pressure, rock becomes metamorphic and fossils are destroyed.
B. Geological Time
1. Sedimentary Rock Layers
a. The law of stratigraphy dates oldest layers at the bottom and youngest at the top.
b. Time is divided into eons, eras, periods and epochs. (See inside back cover.)
2. Radiometric Dating
a. In the late 1940s, this dating method was developed that determines age of rocks.
b. Radioactive decay of naturally occurring elements is independent of heat and pressure.
c. Potassium-Argon Dating
1) Potassium-40 (40K) decays to argon-40 (40Ar) and Calcium-40 (40Ca).
2) Half-life of potassium-40 is 1.3 billion years; half of remainder will be gone at end of
next 1.3 billion years, etc.
3) Calculating the ratio of remaining potassium-40 to amount originally there provides
mathematically close estimate of age of deposit.
d. Rate of decay of uranium into lead can date age of earth itself; error is less than 1% over 2
billion years.
3. Fossil Record of Macroscopic Organisms
a. The Cambrian period of Paleozoic era began about 600 million years ago.
b. Previous Precambrian era occupies 85% of geological time on earth.
c. Little research occurred on Precambrian rocks because they have few oil deposits.
d. Precambrian contains well-preserved fossils of bacteria and algae, casts of lower invertebrates
and many microscopic fossils.
C. Evolutionary Trends
1. Fossil record allows observation of evolutionary change over broad periods of time.
2. Animals species arise and become repeatedly extinct.
3. Animal species typically survive 1-10 million years; there is much variability.
4. Trends are directional changes in features and diversity of organisms.
5. Horse Evolution Shows Clear Trend
a. From Eocene to Recent periods, genera and species of horses were replaced.
b. Earlier horses had smaller sized and fewer grinding teeth, and more toes.
c. Reduction in toes and increase in size and numbers of grinding teeth correlate with
environmental changes.
d. Change occurred in both features of horses and numbers of species.
Trends in fossil diversity are due to different rates of species formation and extinction.
Lineages vary in producing new species or suffering extinction; Darwin provided explanations for
this.
D. Common Descent
1. Darwin proposed that all plants and animals descended from a common ancestor.
2. A history of life forms a branching tree called a phylogeny.
3. This theory allows us to trace backward to determine converging lineages.
4. All forms of life, including extinct branches, connect to this tree somewhere.
5. Phylogenetic research is successful at reconstructing this history of life.
E. Homology and Phylogenetic Reconstruction
1. Darwin saw homology as major evidence for common descent.
2. Richard Owen described homology as “the same organ in different organisms under every variety
of form and function.”
3. Vertebrate limbs show the same basic structures modified for different functions.
4. Darwin’s central idea that apes and humans have a common ancestor was explained by anatomical
homologies.
5. Ground-dwelling birds illustrate homologies.
a. A new skeletal homology arises on each lineage shown.
b. Different groups located at tips of branches contain homologies that reflect ancestry.
c. Branches of the tree combine species into nested hierarchies of groups within groups.
d. Analysis of the living species alone can reconstruct the branching pattern.
e. The pattern of nested hierarchies forms the basis for classification of all forms of life.
f. Structural, molecular, and chromosomal homologies are all combined to reconstruct
evolutionary trees.
g. Older theories that life arose many times forming unbranched lineages fails to predict the
nested hierarchies of lineages; creationism fails to provide testable predictions; all fail as
scientific hypotheses.
F. Ontogeny, Phylogeny and Recapitulation
1. Ontogeny is the history of development of an organism throughout its lifetime.
2. Evolutionary alteration of developmental timing generates new traits allowing divergence among
lineages.
3. German zoologist Ernst Haeckel stated stages of development represented adult forms from
evolutionary history.
4. “Ontogeny recapitulates phylogeny” also became known as recapitulation or the biogenetic law.
5. Haeckel, Darwin’s contemporary, thought that this change was caused by adding new features
onto the end of ancestral ontogeny; but this idea is Lamarckian.
6. Embryologist K.E. von Baer showed early developmental features were simply more widely
shared among different animals groups.
7. However, early development can undergo divergence among lineages too.
8. Evolutionary change in timing of development is called heterochrony.
9. Characteristics can be added late in development and features are then moved to an earlier stage.
10. Ontogeny can be shortened in evolution; terminal stages may be deleted causing adults of
descendants to resemble youthful ancestors.
11. Paedomorphosis is the retention of ancestral juvenile characteristics in descendent adults.
12. Organisms are a mosaic of both; ontogeny rarely completely recapitulates phylogeny.
G. Multiplication of Species
1. Evolution as a Branching Process
a. A branch point occurs where an ancestral species splits into two different species.
b. Darwin’s theory is based on genetic variation.
c. Total number of species increases in time; most species eventually become extinct.
d. Much evolutionary research centers on mechanisms causing branching.
2. Definition of species varies and may include several criteria.
a. Members descend from a common ancestral population.
b. Interbreeding occurs within a species but not among different species.
c. Genotype and phenotype within a species is similar; abrupt differences occur between species.
6.
7.
Reproductive Barriers
a. Reproductive barriers are central to forming new species.
b. If diverging populations reunite, before they are isolated, interbreeding maintains one species.
c. Evolution of diverging populations requires they be kept physically separate a long time.
d. Geographical isolation with gradual divergence provides chance for reproductive barriers to
form.
4. Allopatric Speciation
a. Allopatric populations occupy separate geographical areas.
b. They cannot interbreed because they are separated, but could do so if barriers were removed.
c. Separated populations evolve independently and adapt to different environments.
d. Eventually they are distinct enough they cannot interbreed when reunited.
e. Allopatric speciation occurs in two ways:
1) Vicariant speciation occurs when climate or geology causes populations to fragment;
this may affect many populations at one time but does itself not induce genetic change.
2) Founder effect occurs when a small number of individuals disperse to a distant place;
this has occurred with fruit flies in Hawaii.
f. Hybridization is mating between divergent populations; offspring are hybrids.
g. Premating barriers impair fertilization.
1) Members may not recognize each other.
2) Male and female genitalia may not be compatible.
3) Behavior may be inappropriate to elicit reproduction.
4) Sibling species are indistinguishable in appearance but cannot mate.
h. Postmating barriers impair growth and development or survival.
5. Nonallopatric Speciation
a. When there is no evidence of physical barriers, it is difficult to explain diversity of close
species by allopatric speciation.
b. The huge variety of cichlid fishes in African lakes are found nowhere else; yet lakes are
evolutionarily young and without barriers.
c. Sympatric speciation is the term for the hypothesis that individuals can speciate while living
in different components of the environment.
d. African cichlid fishes are very different in feeding specialization.
e. Parasites may evolve with their host species.
f. It is difficult to observe formation of distinct evolutionary lineages in allopatric speciation.
g. From one-third to one-half of plant species show sympatric evolution using polyploidy; in
animals polyploidy is rare.
6. Adaptive Radiation
a. Adaptive radiation produces diverse species from common ancestral stock.
b. New lakes and islands provide new opportunities for organisms to evolve.
c. Founders who were under heavy competition are now free to colonize the new habitat.
d. The Galápagos Islands provided excellent isolation from mainland and each other.
e. Darwin’s finches are example of adaptive radiation from ancestral finch; finches varied to
assume characteristics of missing warblers, woodpeckers, etc.
H. Gradualism
1. Darwin’s theory of gradualism is based on accumulation of small changes over time.
2. He agreed with Lyell; past changes do not depend on catastrophes not seen today.
3. We observe small, continuous changes; major differences therefore require thousands of years.
4. Accumulation of quantitative changes leads to qualitative change.
5. Ernst Mayr distinguishes between populational gradualism and phenotypic gradualism.
6. Populational gradualism occurs when a new trait becomes more common; this is well
established.
7. Phenotypic Gradualism
a. This theory states that strikingly different traits are produced in a series of small steps.
b. It remains controversial ever since Darwin proposed it.
c. Mutations that cause substantial phenotypic change are called “sports.”
d. Animal breeding has used sports to produce short-legged sheep, etc.
e. Opponents of phenotypic gradualism contend such mutations would be selected against.
3.
f.
I.
Recent work in evolutionary developmental genetics illustrates the continuing controversy
surrounding phenotypical gradualism.
8. Punctuated Equilibrium
a. Phyletic gradualism predicts that fossils would show a long series of intermediate forms.
b. Fossil record does not show the predicted continuous series of fossils.
c. Some Darwinists contend that fossilization is haphazard and slow compared to speciation.
d. Niles Eldridge and Stephen Jay Gould proposed punctuated equilibrium.
e. This theory contends phenotypic evolution is concentrated in brief events of speciation
followed by long intervals of evolutionary stasis.
f. Speciation is episodic with a duration of 10,000 to 100,000 years.
g. Species survive for 5-10 million years; speciation may be less than 1% of species life span.
h. Small fraction of evolutionary history contributes most morphological evolutionary change.
i. Allopatric speciation provides a possible explanation.
1) A small founder population has little chance of leaving fossils that will every be found.
2) After a new genetic equilibrium forms and stabilizes, the larger but different population is
more likely to be preserved.
3) However, punctuated equilibrium occurs in groups where founder events are unlikely.
j. Peter Williamson’s Freshwater Snails
1) Fossil beds in Lake Turkana had a history of earthquakes, eruptions and climate changes.
2) Thirteen lineages of snails show long periods of stability, and brief periods of rapid
change when populations were fragmented by receding waters.
3) Transitions occurred within 5,000 to 50,000 years matching punctuated equilibrium.
Natural Selection
1. Natural selection gives a natural explanation for origins of adaptation.
2. It applies to developmental, behavioral, anatomical and physiological traits.
3. Darwin’s theory of natural selection consists of five observations and three inferences.
a. Organisms have great potential fertility.
1) If all individuals produced would survive, populations would explode exponentially.
2) Darwin calculated that a single pair of elephants could produce 19 million offspring in
750 years.
b. Natural populations normally remain constant in size with minor fluctuations.
1) Natural populations fluctuate in size across generations, sometimes going extinct.
2) No natural populations can sustain exponential growth.
c. Natural resources are limited.
1) Inference: struggle for food, shelter, and space becomes increasingly severe with
overpopulation.
2) Survivors represent only a small part of those produced each generation.
d. All organisms show variation.
e. Some variation is heritable.
1) Darwin only noted the resemblance of parents and offspring.
2) Gregor Mendel’s mechanisms of heredity were applied to evolution many years later.
3) Inference: There is differential survival and reproduction among varying organisms in a
population.
4) Inference: Over many generations, differential survival and reproduction generates new
adaptations and new species.
4. Natural selection can be viewed as a two-part process: random and non-random.
a. Production of variation among organisms is random; mutation does not generate traits
preferentially.
b. The nonrandom component is the survival of different traits.
1) Differential survival and reproduction is called sorting; random processes may sort.
2) Natural selection is sorting that occurs because certain traits give their possessors
advantages relative to others.
c. Orthogenesis was the hypothesis that directed that non-random variation propels evolution.
1) Supposedly, variation has a momentum that forces a lineage to evolve in a direction.
2) The Irish elk supposedly was driven to larger antlers until they became cumbersome and
became extinct.
6.3.
6.4.
3) The disappearance of the Irish elk is not extraordinary and probably not related to the size
of its antlers.
3) This was an explanation for apparently nonadaptive evolutionary trends.
4) Modern genetic research has rejected the genetic predictions of orthogenesis.
d. Some critics contend natural selection cannot generate new structures, only modify old ones.
1) Many structures could not perform their function in early evolutionary stages.
2) However, many structures evolved initially for purposes different from the present.
3) Early feathers functioned in thermoregulation; they later became useful for flight.
Revisions of Darwin’s Theory
A. Neo-Darwinism
1. Darwin did not know the mechanism of inheritance.
a. Darwin saw inheritance as a blending of parental traits.
b. He also considered an organism could alter its heredity through use and disuse of parts.
2. August Weismann’s experiments showed an organism could not modify its heredity.
3. Neo-Darwinism is Darwin’s theory as revised by Weismann.
4. Mendel’s work provided linkage through inheritance that Darwin’s theory required.
5. Ironically, early geneticists thought mutations could cause speciation in a single large step;
selection was merely an eliminator.
B. Emergence of Modern Darwinism: The Synthetic Theory
1. In 1930s, a synthesis occurred that tied together population genetics, paleontology, biogeography,
embryology, systematics and animal behavior.
2. Population genetics studies evolution as change in gene frequencies in populations.
3. Microevolution is change of gene frequency over a short time.
4. Microevolution is evolution on a grand scale, originating new structures and designs, trends, mass
extinctions, etc.
5. The synthesis combines micro- and macroevolution and expands Darwinian theory.
Microevolution: Genetic Variation and Change Within Species
A. The Gene Pool
1. Different allelic forms of a gene constitute polymorphism.
2. All alleles of all genes that exist in a population are collectively the gene pool.
3. Allelic frequency is the frequency of a particular allelic form in a population.
a. Blood types are coded at codominant alleles IA (type A) and IB (type B) and recessive type ii
(O).
b. Since each person carries two alleles; the total numbers of alleles is twice the population size.
c. Blood type frequencies for:
1) France are IA = .46, IB = .14 and i = .40.
2) Russia are IA = .38, IB = .28 and i = .34.
d. Dominance describes the phenotypic effect of an allele only, not its relative abundance.
B. Genetic Equilibrium
1. Whether a gene is dominant or recessive does not affect its frequency; dominant genes do not
supplant recessive genes.
2. In large two-parent populations, genotypic ratios remain in balance unless disturbed.
3. This is called the Hardy-Weinberg equilibrium.
4. It accounts for the persistence of rare traits such as albinism and cystic fibrosis caused by recessive
alleles.
5. Genotype frequency can be calculated by expanding the binomial (p - q)2 where p and q are allele
frequencies.
6. For example, an albino is homozygous recessive and the trait is represented by q2 in the formula:
p2 + 2pq + q2 = 1.
7. Albinos (homozygous recessive) occur in one in 20,000; therefore q2 = 1/20,000 and q = 1/141.
8. Non-albino (p) is 1 - q = 140/141.
9. Carriers would be 2pq or 2 x 140/141 x 1/141 = 1/70; one person in 70 is a carrier.
10. Eliminating a “disadvantageous” recessive allele is nearly impossible.
11. Selection can only act when it is expressed; it will continue through heterozygous carriers.
C. How Genetic Equilibrium is Upset
1. In natural populations, Hardy-Weinberg equilibrium is disturbed by one or more of five factors.
Genetic Drift
a. A small population does not contain much genetic variation.
b. Each individual contains at most two alleles at a single locus; a mating pair has a maximum of
four alleles to contribute for a trait.
c. By chance alone, one or two of the alleles may not be passed on.
d. Chance fluctuation from generation to generation, including loss of alleles, is genetic drift.
e. There is no force causing perfect constancy in allelic frequencies.
f. The smaller the population, the greater the effect of drift.
g. If a population is small for a long time, alleles are lost and response to change is restricted.
3. Nonrandom Mating
a. If two alleles are equally frequent, one half of the population will be heterozygous and one
quarter will be homozygous for each allele.
b. In positive assortative mating, individuals mate with others of the same genotype.
1) This increases homozygous and decreases heterozygous genotypes.
2) It does not change allelic frequencies.
c. Inbreeding is preferential mating among close relatives.
1) Inbreeding increases homozygosity.
2) While positive assortative mating affects one or a few traits, inbreeding affects all
variable traits.
3) Inbreeding increases the chance that recessive alleles will become homozygous and
express.
4) Inbreeding cannot change gene frequencies; genetic drift does and both are common in
small populations.
4. Migration
a. Migration prevents different populations from diverging.
b. Continued migration between Russia and France keeps the ABO allele frequencies from
becoming completely distinct.
5. Natural Selection
a. Natural selection changes both allelic frequencies and genotypic frequencies.
b. An organism that possesses a superior combination of traits has a higher relative fitness.
c. Some traits are advantageous for certain aspects of survival or reproduction and
disadvantageous for others.
d. Sexual selection is selection for traits that obtain a mate but may be harmful for survival.
e. Changes in environment alter selective value of traits making fitness a complex problem.
6. Interactions of Selection, Drift and Migration
a. Subdivision of a species into small populations that exchange migrants promotes rapid
evolution.
b. Genetic drift and selection allow many combinations of many genes to be tested.
c. Migration allows favorable new combinations to spread.
d. Interactions of all factors produce change different from what would result from one alone.
e. Perpetual stability almost never occurs across any significant amount of evolutionary time.
D. Measuring Genetic Variation Within Populations
1. Protein Polymorphism
a. Dominance, interactions between alleles and environmental effects make it difficult to
measure genetic variation from phenotype.
b. Different allelic forms encode proteins with different amino acid sequences; this is protein
polymorphism.
2. Over the last 25 years, geneticists have discovered unexpected variation.
3. Electrophoresis does not detect protein polymorphisms if there are no change differences.
4. Since there is more than one codon for most amino acids, the codons possess more variation.
E. Quantitative Variation
1. Quantitative traits show continuous variation with no Mendelian segregation pattern.
a. Such traits are influenced by variation at many genes.
b. Such traits show a bell-shaped frequency distribution.
2. Stabilizing selection favors the average and trims the extreme.
3. Directional selection favors an extreme value to one side.
2.
6.5.
4. Disruptive selection favors the extremes to both sides and disfavors the average.
Macroevolution: Major Evolutionary Events
A. Speciation links macroevolution to microevolution.
1. The timescale of population genetics processes is from tens to thousands of years.
2. Rates of speciation and extinction are measured in millions of years.
3. Periodic mass extinctions occur in tens to hundreds of millions of years.
a. Five mass extinctions have been dramatic.
b. Study of long-term changes in animal diversity focuses on this longest timescale.
B. Speciation and Extinction Through Geological Time
1. A species has two possible fates: become extinct or give rise to new species.
2. Rates of speciation and extinction vary among species.
3. Lineages with high speciation and low extinction produce the greatest diversity.
4. Lineages whose characteristics increase probability of speciation and confer resistance to
extinction should come to dominate.
5. Species selection is differential survival and multiplication of species based on variation among
lineages.
6. Species-level properties include mating rituals, social structuring, migration patterns, geographic
distribution, etc.
7. Some mammalian lineages have a “harem” system, others do not.
8. Effect macroevolution is similar but differential speciation and extinction is caused by variation
in organismal-level properties rather than species-level properties.
a. Food specialists would therefore be more likely to be geographically isolated.
b. A lineage of specialized grazers and browsers has high speciation and extinction rates.
c. A lineage of generalist grazers and browsers shows neither branching speciation nor
extinction during the same time.
d. Interestingly, the two lineages have similar numbers of individual animals alive today.
C. Mass Extinction
1. Periodic events where huge numbers of taxa go extinct simultaneously are mass extinctions.
2. The Permian extinction occurred 225 million years ago; half of the families of shallow water
invertebrates and 90% of marine invertebrates disappeared.
3. The Cretaceous extinction occurred 65 million years ago and marked the end of the dinosaurs and
many other taxa.
4. Mass extinctions appear to occur at intervals of 26 million years.
a. Some consider them artifacts of statistical or taxonomic analysis.
b. Walter Alvarez proposed that asteroids periodically bombard the earth.
c. Catastrophic species selection would result from selection by these events; for instance,
mammals were able to use resources due to dinosaur extinction.
d. Paleontologist Elisabeth Vrba uses the term Effect Macroevoltuion to describe differential
speciation and extinction rates among lineages caused by organismal-level properties.
Lecture Enrichment
1.
2.
3.
4.
5.
6.
Clarify the fact that Lamarck was the first to try to develop a possible mechanism for evolution. He should be
considered among the great biologists of history, rather than just the “one who got evolution wrong.”
Speculate how Darwin would have reacted to Mendel's work if he had read it; Darwin had a copy of the
publication of Mendel's paper, but the pages had never been cut so that it could be read.
Note that both Darwin and Wallace had extensive travel experiences, where they saw a wide range of
organisms, before they formulated their theory of evolution by natural selection. Biology is so complex and
laden with emergent properties that it is not possible to discover one underlying law, as in physics and
chemistry, and then extrapolate to all cases. The need for a wide range of observational experiences in biology
is therefore a difference in philosophy of science between the life and physical sciences that many students will
not perceive.
In a modern age of public relations, few students will comprehend why Darwin waited over twenty years from
his seminal trip on the HMS Beagle to publish his theory. One of the topics to consider is Darwin's feelings for
his wife, who was a very religious woman, and the impact that the theory of natural selection and evolution had
on those who considered the theory of special creation to be absolute truth, which students should understand.
Students do not immediately internalize the meaning of terms such as “allopatric” and “sympatric.” Since you
will not be using these terms across the course, the concept is most efficiently taught using examples and
referring to the cases rather than generalizing.
Students who have already completed a course in botany will have an understanding of the ability of plants
to speciate sympatrically via polyploidy. Other students will be puzzled why animals and plants vary so
greatly on this issue.
Commentary/Lesson Plan
Background: The concepts of multiple alleles and recombination are not explained in many secondary biology
texts. Algebra skills are necessary for students to understand the Hardy-Weinberg formula and high school math
requirements vary by state. Some African-American students will be very aware of the sickle-cell gene. The comet
and meteorite impact theories have gone from speculative to fairly well accepted in the last decade and the instructor
will probably face students who were taught the previous uncertainties. Breaking news on recent major fossil finds
in China and Africa make evolution a timely topic to cover. And new discoveries requiring reinterpretation of our
phylogeny will cause this chapter to present new or different concepts from what students may have learned in high
school biology. Visuals of fossils will help students see the distinctions described in this chapter. Some students
will have some concerns with this chapter based on religious background but an honest and clear explanation of the
current status of our science knowledge should help.
Misconceptions: Most students view mutations as rare and the only source of genetic variation. Dinosaurs are a
hot topic now covered heavily in K-12 science curricula; however, new developments make many textbooks
obsolete; therefore, the college instructor will have to deal with many misconceptions. Some students and even
molecular biologists will not understand why classifications change–why can’t systematists just settle on one set of
higher taxa and stick with it? While ongoing changes may seem casual and arbitrary, there is a complex rationale
for the evolutionary schema that students can understand.
Schedule: An instructor may vary considerably in how much background history, philosophical setting, etc. to
provide before introducing Darwin’s voyage, etc. Speed of coverage of population genetics concepts will also vary
greatly depending on students’ previous coursework.
HOUR 1 4.1.
4.2.
HOUR 2
4.3.
HOUR 3 4.4.
4.5.
Origins of Darwinian Evolutionary Theory
A. Pre-Darwinian Evolutionary Ideas
B. Darwin’s Great Voyage of Discovery
Darwinian Evolutionary Theory: The Evidence
A. Perpetual Change
B. Geological Time
C. Evolutionary Trends
D. Common Descent
E. Homology and Phylogenetic Reconstruction
F. Ontogeny, Phylogeny and Recapitulation
G. Multiplication of Species
H. Gradualism
I. Natural Selection
Revisions of Darwin’s Theory
A. Neo-Darwinism
B. Emergence of Modern Darwinism: The Synthetic Theory
Microevolution: Genetic Variation and Change Within Species
A. The Gene Pool
B. Genetic Equilibrium
C. How Genetic Equilibrium is Upset
D. Measuring Genetic Variation Within Populations
E. Quatitative Variation
Macroevolution: Major Evolutionary Events
A. Speciation links macroevolution to microevolution.
B. Speciation and Extinction Through Geological Time
C. Mass Extinctions
ADVANCED CLASS QUESTIONS:
1. Will evolution occur if there is no variation in a population, if the only variation is acquired and not inherited or
if all progeny survive and equally reproduce?
2 Could bacteria and humans possibly share a common ancestor; and what evidence do we have?
3. Why are an insect wing and a bird wing not considered evidence of relatedness?
4. The presence of vestigial structures suggests that the process of adaptation is not necessarily purposeful. Why?
5. How can the scientific method be used to test the concept of evolutionary descent if no one was present in the
past to witness it?
6. Why is adaptive radiation more prevalent when there is less competition, as in the case of the finches on the
Galápagos or the mammals following the dinosaur extinction?
Twelfth Edition Changes:
1.
2.
3.
4.
5.
Only minor changes were made to the content of this chapter:
It was stated that the Earth’s rock strata record the irreversible, historical change that we call organic
evolution.
Paleontologist Elisabeth Vrba’s contribution to effect macroevolution is described.
Recent work in evolutionary developmental genetics illustrates the continuing controversy surrounding
phenotypic gradualism.
Because extinction is the expected evolutionary fate of most species, disappearance of the Irish elk is not
extraordinary and was probably not related to the size of its antlers.
New or upgraded figures and tables include Darwin’s Explanatory Model of Evolution.
Source Materials
[Bold = recommended; for vendor abbreviations, see list of distributors in Appendix 1]
Ancient Forests (NGS), 25-min. video
Behavior and the Protein Record (FH), 20-min. video
Beyond Genesis: Darwin's The Origin of Species (FH), 50-min. video
The Big Bang and Beyond (FH), 26-min. video
The Blind Sequence Maker (OAK), MS-DOS
Charles Darwin (FH), 11-min. video
Charles Darwin (UC) (IM), 24-min. video
Charles Darwin Explains the Diversity of Life (HH), 21-min. video
Climbing Mount Improbable (FH), 58 -min. video
The Creationist Argument (FH), 26-min. video
Cycles of Life: Exploring Biology–Macroevolution (A-CPB), 30-min. video
Cycles of Life: Exploring Biology–Microevolution (A-CPB), 30-min. video
Cycles of Life: Exploring Biology–The Unity and Diversity of Life (A-CPB), 30-min. video
Darwin, Naturally (FH), 10-min. video
Darwin and the Theory of Natural Selection (PHO), 13-min. video
Darwin's Finches: Clues to the Origin of Species (PHO), 11-min. video
Darwin's Theory Today (FH), 26-min. video
Darwin's Voyage of the Beagle (INT), Mac
Designed and Designoid Objects (FH), 58-min. video
Did Darwin Get It Wrong? (T/L), 57-min. video
Dinosaur! (FREY), 200-min. in 4 videos
The Dinosaur's Age (PHO), 15-min. video
DNA and the Evidence for Evolution (FH), 20-min. video
Early Stone Tools (UC), 20-min. video
Earth Revealed (A-CPB), 8 1-hr. videos
The Earth's Five Kingdoms (JLM), slide set (20)
The Evidence for Evolution (FH) (IM), 30-min. video
Evolution (CBSC), 91-min. video
Evolution (CBSC), Mac, MS-DOS CD
Evolution (FH), 23-min. video
Evolution (HH) (WARDS), 38-min. video
Evolution (WARDS), Mac, Win, MS-DOS CD-ROM
Evolution (VDISC), laserdisc
Evolution of Darwin Series (6 selections) (FH), 26-min. videos
The Evolution of Life and Man (Q), Mac or MS-DOS CD
Evolution and Life’s Diversity (WARDS), Mac
The Evolution of Human Purpose (FH), 26-min. video
The Evolution of Man (FH), 24-min. video
Evolution of Man Slide Set (WARDS), 45 slides and guide
Evolution Part I: Anaximander to Darwin and Beyond (HH), video
Evolution Part II: Evolution by Natural Selection (HH), video
Evolution: A Simulation (OAK), Mac
Evolution: The Evidence for Modern Ideas on Evolution Series (11 selections) (FH), 20-min. each videos
Evolution Update (IM), 30-min. video
Evolution and the Origin of Life (CRM), 36-min. video
Evolutionary Biology (PHO), 16-min. video
Evolve: Time and Taxonomy (PLP), Apple, MS-DOS
Expansion of Life (IM), 58-min. video
First Person: Stephen J. Gould on Evolution (CAM), Mac CD
Fossils of the Precambrian and Lower Paleozoic I and II, Middle and Upper Paleozoic I and II, Mesozoic I and II,
Cenozoic I and II (JLM), slide sets (20 each)
Fossils: Clues to the Past (NGS), 23-min. video
Fossils and Fossilization (JLM), slide set (20)
Fossils: Plants and Tetrapods (FH), 20-min. video
Fossils: Reptiles and Mammals (FH), 20-min. video
Galápagos Albatross (UC), 11-min. video
Galápagos Cactus and Scalesia (UC), 13-min. video
Galápagos: Darwin's World Within Itself (EBE), 11-min. video
Galápagos Finches (UC), 21-min. video
The Galápagos Islands (HH), 20-min. video
Galápagos Tortoise (UC), 23-min. video
Gardens of Biology II: Evolution (INT), Mac
The Genesis of Purpose (FH), 58-min. video
Genetic Polymorphisms and Evolution (MF), 16-min. video
Genetic Vulnerability: A Field Study of the Cheetah (PLP), Apple
How Scientists Know About Evolution (UC), 18-min. video
How Scientists Know About Punctuated Equilibrium (UC), 20-min. video
The Human Influence (FH), 20-min. video
In the Beginning (FH), 10-min. video
Ladder of Creation [Ascent of Man Series] (AVP), 52-min. video
Life of the Precambrian and Lower Paleozoic, Middle and Upper Paleozoic, Mesozoic, Cenozoic (JLM), slide sets
(30-40 each)
Lower Than the Angels [Ascent of Man Series] (AVP), 52-min. video
The Making of Mankind (AVP), 7-part series of 60-min. videos
Multiple Gene Population Simulation (OAK), MS-DOS
The Mutation Machine (FH), 26-min. video
Mysteries of Mankind (FREY), 60-min. video
Natural Selection (FH), 20-min. video
Natural Selection (EBE) (HRM), 16-min. video
Natural Selection (IM), 30-min. video
Natural Selection (EME) (CBSC), Apple, MS-DOS
Natural Selection (EME), Mac, MS-DOS CD-ROM
NOVA: In Search of Human Origins Series (CBSC) (FREY) (PLP), 3 57-min. videos
NOVA: Case of the Flying Dinosaur (CBSC) (PLP), 57-min. video
On the Trail of the Thick-Skulled Dinosaur (BSA) 50-min. video
Organic Evolution (IM), 60-min. video
Organic Evolution (WARDS), 6 10-min. videos
Origin of Cellular Life (ei), slide
Origins of Change (FH), 20-min. video
The Origin of Species (Creationism and Evolution) (HH), 22-min. video
The Origins of Darwin's Theory (FH), 26-min. video
Origin of Life (EME) (PLP), Apple, MS-DOS
Origins of Change: Parts I and II (FH), 20-min. video
Paleontology (IM), 40-min. video
The Peppered Moth–A Population Study (BSCS Classic Inquiry) (MDA), videodisc
The Popular Picture [Hardy-Weinberg] (FH), 10-min. video
Population Concepts (EME), Apple, MS-DOS
Population Genetics (PLP), Apple, MS-DOS
Population Genetics Simulation (OAK), MS-DOS
Population Genetics Tutorial (OAK), MS-DOS
Population Picture (FH), 10-min. video
The Record of the Rocks (FH), 20-min. video
Retracing Man's Steps (FH), 28-min. video
Richard Leakey (CBSC), 35-min. video
Ritual of the Spring Tide [horseshoe crab and evolution] (PYR), 17-min. video
Rocks That Reveal the Past (PHO) (BFA), 12-min. video
Stephen Jay Gould (CBSC), 28-min. video
Selection and Adaptation (FH), 20-min. video
Selection in Action, Parts I, II, III (FH), 20-min. each, video
Sources of Variety (ei), slides or video
Speciation (ei), slides or video
Species Diversity (INT), Mac
Structural Homologies and Coevolution (FH), 20-min. video
Three Billion Years of Life: The Drama of Evolution (GA), 70-min. video
Tobias on the Evolution of Man (NGS), 18-min. video
The Ultraviolet Garden (FH), 58-min. video
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
CHAPTER
5
THE REPRODUCTIVE PROCESS
CHAPTER OUTLINE
5.1.
Nature of the Reproductive Process
A. Mechanisms (Figure 5.1)
1. Asexual reproduction involves only one parent.
a. There are no special reproductive organs or cells involved.
b. Genetically identical offspring are produced.
c. Production of offspring is simple, direct and rapid.
2. Sexual reproduction generally involves two parents.
a. Special germ cells (gametes) unite to form a zygote.
b. By receiving genetic material from both parents, the offspring are unique.
c. Sexual reproduction recombines parental characters and makes possible a richer and more
diversified population.
3. In haploid asexual organisms, mutations are expressed and selected quickly.
4. In sexual reproduction, a normal gene on the homologous chromosome may mask a gene
mutation.
B. Asexual Reproduction: Reproduction Without Gametes
1. Neither eggs nor sperm are involved.
2. Unless mutations occur, all offspring have the same genotype and are clonal.
3. Asexual reproduction is widespread in bacteria, unicellular eukaryotes and many invertebrate
phyla.
4. Asexual reproduction ensures rapid increase in numbers.
5. Binary fission is common among bacteria and protozoa.
a. The parent divides by mitosis into two parts; each grows into an individual similar to the
parent.
b. Binary fission can be lengthwise or transverse.
c. In multiple fission, the nucleus divides repeatedly; cytoplasmic division produces many
daughter cells.
d. Sporogony is spore formation, a form of multiple fission in parasitic protozoa.
6. Budding is unequal division of an organism.
a. The bud is an outgrowth of the parent; it develops organs and then detaches.
b. Budding occurs in cnidarians and some other animal phyla.
7. Gemmulation is formation of a new individual from an aggregation of cells from the parent
individual surrounded by a resistant capsule (gemmule).
a. Freshwater sponges survive winter in the dried or frozen body of the parent.
b. In good conditions, the enclosed cells become active, emerge and grow a new sponge.
8. Fragmentation involves a multicellular animal breaking into many fragments that become a new
animal.
C. Sexual Reproduction: Reproduction With Gametes
1. Bisexual Reproduction
a. Also called biparental, bisexual reproduction produces offspring from union of gametes
from two genetically different parents.
b. Offspring therefore have a genotype different from either parent. (Figure 5.2)
c. Generally, individuals are male or female and produce spermatozoa or ova, respectively.
1) The female produces the ovum; it is large with stored yolk and is nonmotile.
2) The spermatozoon is produced by the male; it is small, motile and much more numerous.
d. Most vertebrates and many invertebrates have separate sexes; they are dioecious.
e. Some animals have both male and female organs; they are monoecious or hermaphrodites.
f. Meiosis (duplication and two divisions) produces four haploid cells.
g. In fertilization, two haploid cells combine to restore the diploid chromosome number in the
zygote.
h. A zygote divides by mitosis for all somatic (body) cells.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
i.
j.
5.2.
Many unicellular organisms can reproduce both sexually and asexually.
When sexual parents merely join together to exchange nuclear material (conjugation), distinct
sexes do not occur.
k. Organs that produce germ cells are gonads; testes produce sperm and ovaries produce eggs.
l. Gonads are primary sex organs; some animals lack any other “accessory” sex organs.
m. Additional accessory sex organs include penis, vagina, uterine tubes and uterus.
2. Hermaphroditism (Figure 5.3)
a. Hermaphrodites have both male and female organs in the same individual.
b. Many sessile, burrowing and/or endoparasitic invertebrate animals and a few fish are
hermaphroditic.
c. Most avoid self-fertilization and exchange germ cells with another member of the same
species.
d. Each individual is reproductive, in contrast to dioecious species where about half is male.
e. In sequential hermaphroditism, a fish starts life as one sex and is genetically programmed to
change to the other sex later.
3. Parthenogenesis
a. Parthenogenesis is the development of an embryo from an unfertilized egg.
b. The male and female nuclei may fail to unite after fertilization.
c. In ameiotic parthenogenesis, no meiosis occurs and the egg forms by mitotic division.
d. In meiotic parthenogenesis, the haploid ovum is formed by meiosis and develops without
fusion with the male nuclei.
1) Sperm may be absent or they may only activate development.
2) In some species, the haploid egg returns to a diploid condition by chromosomal
duplication.
e. Haplodiploidy occurs in bees, wasps and ants.
1) The queen controls whether the eggs are laid fertilized or unfertilized.
2) Fertilized eggs become female workers or queens; the unfertilized eggs become drones.
f. Some desert lizards have modified meiosis so offspring are clones of the female parent.
g. Parthenogenesis avoids the energy and dangers of bringing two sexes together; but it narrows
the diversity available for adaptation to new conditions.
4. Why do so many animals reproduce sexually rather than asexually? (Figure 5.4)
a. Sexual reproduction is more common among animals.
b. The costs of sexual reproduction are greater.
1) It is more complicated, requires more time and uses more energy than asexual.
2) The cost of meiosis to the female is passage of only half of her genes to offspring.
3) Production of males reduces resources for females that could produce eggs.
c. Sexual organisms produce more novel genotypes to survive in times of environmental change.
d. Asexual organisms can have more offspring in a short time to colonize new environments.
e. In crowded habitats, selection is intense and diversity prevents extinction.
f. On a geological time scale, asexual lineages with less variation are prone to extinction.
g. Many invertebrates with both sexual and asexual modes enjoy the advantages of both.
Origin and Maturation of Germ Cells
A. Germ Cells
1. Somatic cells are non-reproductive body cells; they differentiate, function and die before or with
the animal.
2. Germ cells form gametes; the germ cell line provides a continuous line between generations.
3. Somatic cells support, protect and nourish the germ cell line.
4. The germ cell lineage may be traceable; in some invertebrates, the germ cells develop from
somatic cells.
B. Migration of Germ Cells (Figure 5.5)
1. Vertebrate gonads arise from a pair of genital ridges that grows into the coelom from the dorsal
coelomic lining on each side of the hindgut near the anterior end of the kidney.
2. Primordial germ cells themselves arise from yolk-sac endoderm, not the developing gonad.
3. Germ plasm from the vegetal pole of the uncleaved egg mass moves to gut endoderm and
migrates by ameboid movement to genital ridges.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
4. Germ cells divide first by mitosis, increasing from a few dozen to several thousand.
C. Sex Determination
1. Originally gonads are sexually indifferent.
2. In human males, SRY (sex determining region Y) on the Y chromosome organizes the gonad into
a testis.
3. Formed as a testis, it secretes testosterone which, with dihydrotestosterone (DHT), masculinizes
the fetus; causing development of a penis, scrotum and male glands.
4. In the brain, testosterone is enzymatically converted to estrogen, which determines brain
organization for male-typical behavior.
5. A region of the X chromosome named DDS (dosage sensitive sex reversal) or SRVX (sex
reversing X) can promote ovary formation.
6. However, absence of testosterone in a genetic female embryo promotes development of female
sexual organs: vagina, clitoris and uterus.
7. Despite levels of estrogen, the female brain does not become masculinized perhaps due to low
estrogen receptors.
8. Genetics of sex determination vary: XX-XY, XX-XO, haplodiploid, temperature, etc. [see Ch. 5].
(Figure 5.6)
D. Gametogenesis
1. Gametogenesis is the series of transformations that result in gametes.
2. Testes carry out spermatogenesis; ovaries carry out oogenesis.
3. Spermatogenesis
a. The wall of seminiferous tubules contains germ cells five to eight cells deep. (Figure 5.7)
b. Sustentacular (Sertoli) cells extend from the periphery to nourish germ cells. (Figure 5.8)
c. The outermost layers are spermatogonia, diploid cells that have increased by mitosis.
d. A spermatogonium increases in size to become a primary spermatocyte.
e. A primary spermatocyte undergoes the first meiotic division to become two secondary
spermatocytes.
f. Without resting, each secondary spermatocyte enters the second meiotic division to produce
four haploid spermatids.
g. Spermatids transform into mature spermatozoa (sperm).
1) Most cytoplasm is lost.
2) The haploid nucleus condenses into a head.
3) A midpiece forms containing mitochondria.
4) The whiplike flagellar tail provides locomotion.
h. The sperm head contains an acrosome (except for some fishes and invertebrates).
1) Often the acrosome contains lysins to clear an entrance through layers surrounding the
egg.
2) In mammals, one lysin is hyaluronidase; it allows sperm to penetrate follicular cells
around the egg.
3) In many invertebrate sperm, an acrosome filament extends suddenly upon contact with
surface of the egg.
i. Fusion of egg and sperm plasma membranes is initial event for fertilization.
j. Size of sperm varies from 50 µm to 2 mm in length; most are very small. (Figure 5.9)
k. Sperm greatly outnumber eggs.
4. Oogenesis
a. Oogonia are early germ cells in the ovary; they are diploid and increase by mitosis.
b. They cease to grow in number and increase in size as primary oocytes. (Figure 5.10)
c. Chromosomes pair in the first meiotic division, similar to spermatogenesis.
d. In this first division, the cytoplasm is divided unequally.
e. Larger daughter cell or secondary oocyte receives most of the cytoplasm; the rest goes to the
first polar body.
f. In the second meiotic division, the secondary oocyte forms a large ootid and a small polar
body.
g. Since the first polar body also divides, this produces three polar bodies that disintegrate.
h. The ootid forms a functional ovum with sufficient yolk.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
i.
j.
5.3.
5.4.
Unlike spermatogenesis that forms four gametes, oogenesis forms one haploid ovum.
Most vertebrate and some invertebrate eggs wait for fertilization to complete the last
meiotic divisions.
1) Development is arrested in prophase I; meiosis resumes at ovulation or after fertilization.
2) Human ova begin the first meiotic division at the thirteenth week of fetal development.
3) Human ova arrest development in prophase I until puberty.
4) After puberty, some oocytes develop into functional eggs; meiosis II is completed only
after penetration by a spermatozoon.
k. Yolk
1) Egg maturation involves deposition of yolk.
2) Yolk is stored as granules of lipid, protein or both.
3) Yolk may be synthesized internally or supplied from follicle cells.
4) Accumulation of yolk granules and nutrients cause eggs to grow massively beyond
normal cell size.
l. The size of an egg violates surface-area-to-volume ratios; it therefore slows metabolism.
Reproductive Patterns
A. Live-birth Versus Egg-bearing
1. Oviparous animals lay eggs in the environment for development.
a. Fertilization may be internal (before eggs are laid) or external (after laid).
b. Some animals abandon eggs; others provide extensive care.
2. Ovoviviparous animals retain eggs in their body.
a. Essentially all nourishment is derived from the yolk.
b. This is common in some invertebrate groups and certain fishes and reptiles.
c. Fertilization is internal.
3. Viviparous animals give live birth.
a. Eggs develop in an oviduct or uterus.
b. Embryos continuously derive nourishment from the mother.
c. Fertilization is internal.
d. This occurs in mammals and some fishes; it provides more protection to offspring.
Plan of Reproductive Systems
A. Components
1. Primary organs are the gonads that produce sperm, eggs and sex hormones.
2. Accessory organs assist gonads in formation and delivery of gametes and may support embryos.
B. Invertebrate Reproductive Systems (Figure 5.11)
1. Invertebrates that transfer sperm for internal fertilization require complex organs.
2. Invertebrates that release sperm into water for external fertilization may be simple.
a. Polychaete annelids have no permanent reproductive organs; gametes are cells from the body
cavity.
b. Mature gametes may be released through ducts or spill out through ruptures.
3. Insects have separate sexes and accomplish internal fertilization using complex systems.
a. Sperm from testes are stored in seminal vesicles before ejaculated.
b. Female insects have ovaries in a series of egg tubes.
c. Mature ova pass to a common genital chamber and short vagina.
d. Sperm inserted by male are stored in a seminal receptacle in female.
e. One mating may provide enough sperm to last the reproductive life of a female insect.
C. Vertebrate Reproductive Systems
1. Urogenital system of vertebrates shows close connections of reproductive and excretory systems.
2. The mesonephric duct drains the kidney and carries sperm in male fishes and amphibians.
3. The mesonephric duct is composed of the vas deferens and a separate ureter develops in male
reptiles, birds and mammals.
4. The cloaca is the common chamber for intestinal, reproductive and excretory canals, except in
mammals.
5. The uterine duct of the oviduct has an independent duct opening into cloaca when present.
D. Male Reproductive System
1. Paired testes are sites of sperm production.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Testes contain numerous seminiferous tubules where sperm develop. (Figure 5.12)
Sperm are surrounded by sustentacular cells that nourish developing sperm.
Between tubules are interstitial cells that produce testosterone.
A sac-like scrotum suspends testes outside the warm body cavity; the lower temperature of
scrotum is vital to normal sperm production.
6. Sperm pass from the testes to vasa efferentia and to coiled epididymis for maturation.
7. The vas deferens carries sperm from the epididymis to the urethra, where it exits the penis.
8. The penis is a copulatory organ used to introduce spermatozoa into the female vagina.
9. Seminal vesicles, prostate gland and bulbourethral glands form seminal fluid.
a. Seminal vesicles secrete a thick fluid containing nutrients for use by sperm.
b. The prostate gland secretes a milky, slightly alkaline solution that counters acidity.
c. Bulbourethral glands release mucus secretions that provide lubrication.
E. Female Reproductive System
1. Ovaries in female vertebrates produce ova and the female sex hormones, estrogen and
progesterone.
2. In jawed vertebrates, mature ova from ovaries enter funnel-like uterine tubes or oviducts.
3. The terminal end of uterine tube is specialized in cartilaginous fishes, reptiles and birds to produce
shelled eggs; special regions produce albumin and shell.
4. The terminal portion of amniote uterine tube expands into a muscular uterus.
a. Shelled eggs may be retained here before laying.
b. Embryos may complete their development here.
c. Placental mammals use the walls of the uterus to intermingle vascular tissue as a placenta.
5. Ovaries are paired and slightly smaller than male testes. (Figure 5.13)
a. Oocytes develop within a follicle that enlarges to release a secondary oocyte. (Figure 5.10)
b. Unless fertilization occurs, women release about 13 oocytes per year, 300-400 per a 30-year
reproductive lifetime.
c. 300-400 primary oocytes, of ca. 400,000 in ovaries at birth, reach maturity while the rest
degenerate and are absorbed.
6. Uterine tubes or oviducts are lined with cilia that propel the egg.
7. The oviducts enter the upper corners of the uterus.
8. Uterus
a. The uterus is specialized to house the embryo for nine months.
b. The uterus has thick muscular walls and is stretchable.
c. The endometrium is the specialized lining rich in blood vessels.
d. Ancestrally, the uterus was paired but is fused in eutherian mammals.
9. The vagina is muscular tube that receives the male’s penis and serves as birth canal.
10. The cervix is the end of the uterus that extends into the vagina.
11. The vulva is external genitalia in human females.
a. Labia majora and labia minora enclose urethral and vaginal openings.
b. The clitoris is a small erectile organ equivalent to the glans penis of male.
Endocrine Events that Orchestrate Reproduction
A. Hormonal Control of Timing of Reproductive Cycles
1. Vertebrate reproduction is seasonal or cyclic to align with food supply and survival of young.
2. Sexual cycles are controlled by hormones that respond to food intake, photoperiod, rainfall,
temperature or social cues.
3. Estrous Cycles
a. Females are receptive to males only during brief periods of estrus or “heat.”
b. The estrous cycle ends with uterine lining reverting to original state; there is no menstruation.
4. Menstrual Cycles
a. This cycle occurs in monkeys, apes and humans.
b. Females are receptive to males throughout the cycle.
c. At the end of the menstrual cycle the endometrium (uterine lining) is discharged.
B. Gonadal Steroids and Their Control (Figure 5.14)
1. Ovaries produce estrogens and progesterone.
2. The three estrogens include estradiol, estrone and estriol.
2.
3.
4.
5.
5.5.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
3.
Estrogen Functions
a. Estrogens develop female accessory sex structures: oviducts, uterus and vagina.
b. Estrogens stimulate female reproductive activity.
c. Secondary non-reproductive characteristics include
1) skin or feather coloration,
2) bone development,
3) body size, and
4) initial development of mammary glands in mammals.
4. Both estrogen and progesterone prepare the uterus to receive an embryo. (Figure 5.15)
a. The hypothalamus produces gonadotropin releasing hormone (GnRH).
b. GnRH governs pituitary release of follicle-stimulating hormone (FSH) and luteinizing
hormone (LH).
c. Light, nutrition, stress, etc. can influence this complex feedback system.
5. Testosterone
a. Interstitial cells in testes manufacture testosterone.
b. Testosterone and its metabolite dihydrotestosterone (DHT) are required for growth of the
penis, sperm ducts, and glands, and secondary sexual traits.
c. Secondary non-reproductive characteristics include
1) male plumage and pelage coloration,
2) bone and muscle growth,
3) antlers in deer, and
4) vocal cord growth in humans.
d. Testosterone and DHT feedback to hypothalamus and anterior pituitary to keep secretion of
GnRH, FSH and LH in check.
e. Sustentacular cells of testes secrete inhibin; it regulates FSH of anterior pituitary by negative
feedback.
C. The Menstrual Cycle
1. The ovary has two phases: follicular and luteal.
2. The uterus has three phases: menstrual, proliferative and secretory. (Figure 5.16)
3. Menstruation, shedding of the uterine lining, signals the menstrual phase.
4. The follicular phase of ovary is also occurring.
a. By day three of the menstrual cycle, blood levels of FSH and LH rise slowly, prompting some
ovarian follicles to grow and secrete estrogen.
b. As estrogen increases, the uterine endometrium heals and begins to thicken.
c. Uterine glands within the endometrium enlarge in the proliferative phase of uterus.
d. By day 10, most ovarian follicles degenerate (become atretic) leaving one, two or three to
continue ripening.
e. Final mature follicle is the Graafian follicle; it secretes more estrogen and also inhibin.
f. At day 13 or 14, high levels of estrogen from the Graafian follicle stimulate a surge in GnRH
from hypothalamus.
g. This stimulates a surge of LH and some FSH from anterior pituitary.
h. The LH surge causes the largest follicle to rupture and release an oocyte (ovulation).
5. The luteal phase of the ovary is named for the corpus luteum, which is the remainder of the
ruptured follicle.
a. The corpus luteum responds to LH and secretes progesterone.
b. Progesterone stimulates the uterus to undergo maturation and prepare for gestation.
c. If an embryo implants, the uterus enters the secretory phase.
d. If fertilization does not occur, the corpus luteum degenerates and hormones are no longer
secreted.
e. The uterus depends on progesterone and estrogen to maintain uterine lining; declining levels
start endometrium degeneration and lead to menstrual discharge.
6. Negative feedback among the hypothalamus, anterior pituitary and ovary control the cycle.
7. Ovulation is due to high levels of estrogen causing a surge in GnRH, LH and FSH; such positive
feedback is rare since it moves events away from stable set points.
D. Hormones of Human Pregnancy and Birth
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Copyright © 2005 – The McGraw-Hill Companies srl
1.
2.
3.
4.
5.
Fertilization normally occurs in the outer third of the uterine tube (ampulla).
As the zygote travels to uterus, it divides by mitosis to form a blastocyst.
In about six days, on contact with the uterine lining, it buries in the endometrium (implantation).
The spherically-shaped trophoblast contains three layers: amnion, chorion and embryo proper.
The chorion is a source of human chorionic gonadotropin (hCG); it stimulates the corpus luteum
to produce estrogen and progesterone.
6. The placenta is formed between the trophoblast and uterus.
a. The placenta is an endocrine gland, secreting hCG, estriol, and progesterone.
b. The placenta also transfers nutrients and wastes between mother and fetus.
c. After a month, the corpus luteum degenerates and the placenta itself holds the lining by
progesterone and estrogen. (Figure 5.17)
7. Preparation of mammary glands to secrete milk requires two additional hormones.
a. Prolactin (PRL) is produced by the anterior pituitary, but is inhibited in non-pregnant
women.
b. During pregnancy, elevated progesterone and estrogen depress inhibition and PRL appears in
the blood.
c. Human placental lactogen (hPL) aids PRL in preparing the mammary glands for secretion.
d. Together with maternal growth hormone, hPL stimulates an increase in nutrients in the
mother.
e. The placenta later synthesizes peptide hormone relaxin to allow expansion of pelvis by
flexibility of pubic symphysis.
f. Relaxin also dilates the cervix in preparation for delivery.
8. Birth or parturition begins with rhythmic contractions of uterus called labor.
a. Estrogen secreted before birth stimulates contractions.
b. Progesterone levels, which inhibit contraction, decline.
c. Prostaglandin hormones increase, making the uterus more irritable.
d. Uterine stretching causes neural reflexes to stimulate secretion of oxytocin from the posterior
pituitary.
e. Oxytocin stimulates uterine smooth muscle contractions.
f. Childbirth (Figure 5.18)
1) First stage: the cervix enlarges and the amniotic sac will rupture.
2) Second stage: the baby is forced out of the uterus and through the vagina.
3) Third stage: the placenta or afterbirth is expelled.
g. Milk Production
1) Milk production is triggered when infant sucks on the mother’s nipple.
2) Stimulation leads to reflex release of oxytocin from the pituitary.
3) Oxytocin causes contraction of smooth muscles lining ducts of mammary glands.
4) Suckling also stimulates release of prolactin, which continues milk production.
E. Multiple Births (Figure 5.19)
1. Many mammals are multiparous, giving birth to many offspring at one time.
2. Some give birth only to one at a time; they are uniparous.
3. Exceptions occur; the armadillo gives birth to four young, all male or all female, derived from one
zygote.
4. Monozygotic, or identical, twins are derived from one zygote; they have identical genomes.
5. Fraternal, dizygotic or nonidentical, twins are from two zygotes and may not resemble each other
any more than other siblings.
6. Identical Twins
a. They may separate early and have separate placentas.
b. Two-thirds share a placenta and splitting occurred after formation of the inner cell mass, but
most have individual amniotic sacs.
c. A few share one amniotic sac and a single placenta; separation of the zygote occurred after
day 9 of pregnancy when the amnion has formed; these twins risk becoming conjoined
(Siamese twinning).
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Lecture Enrichment
1.
2.
3.
4.
5.
Discuss the procession to internal egg fertilization as a requirement for life on land. Contrast the shelled eggs of
reptiles and birds, the egg cases of insects and the internal development of the fetus in mammals. Discuss how
each is adapted to prevent desiccation.
Have students trace the path of sperm from its development in the testes to its release during ejaculation; ask for
the additions of glandular secretions along the way.
Research shows that when sperm enters the egg, the mitochondrial mid-piece and parts of the tail also enter.
However, there are far fewer sperm mitochondria and they are worn out, and the egg tags them for cell
destruction. Thus, a person inherits all of his mitochondria from his/her biological mother.
Have students trace the path of the egg as it develops in the ovary and is released. They should describe what
happens to the egg if it is fertilized or if it is not fertilized.
The description of the hormonal feedback of the menstrual cycle is sufficient to allow students to think through
the mechanism of the birth control pill.
Commentary/Lesson Plan
Background: Due to American society’s preoccupation with this topic, this is generally the highest interest topic in
biology. Student experiences in this subject may be varied; students from rural areas may still have experiences
with animal birth, breeding, litters, etc. However, the social context may prevent using some student testimonials
and experiences.
Misconceptions: The term “germ” has far more recognition in meaning as a pathogen or microbe than as “germinal
lineage.” It is also not easy for students to comprehend the germ line as an immortal cell lineage where we are
individual temporary support systems for this cell lineage—a particularly biological viewpoint. “Womb” is a
nonfunctional term since it has historically been used for ovaries as well as uterus. “Hermaphrodites” and
“bisexual” have social meanings different from their biological usage here. Ambiguous human sexual development
is rarely truly hermaphroditic (see John Money and Anke Erhardt’s Man and Woman, Boy and Girl), but
hermaphroditism has genuine advantages for organisms isolated in soil or hosts. Woody Allen’s famous quote that
bisexuality doubles your chances of a date on Friday evening clearly explains the advantages of hermaphroditism
and also reveals the different social usage of “bisexual” from the scientific meaning for this term. Basic bisexual
reproduction refers to the separate male and female organism system we use, but it will be difficult for some
students to associate this with human heterosexuality.
Schedule: Time spent on this chapter may vary greatly depending on how much an instructor wishes to elaborate on
the examples and wide diversity of animal reproductive systems.
HOUR 1 5.1.
5.2.
HOUR 2 5.3.
5.4.
Nature of the Reproductive Process
A. Mechanisms
B Asexual Reproduction:
Reproduction Without Gametes
C. Sexual Reproduction:
Reproduction With Gametes
Origin and Maturation of Germ Cells
A. Germ Cells
B. Migration of Germ Cells
C. Sex Determination
D. Gametogenesis
Reproductive Patterns
A. Live-birth Versus Egg-bearing
Plan of Reproductive Systems
A. Components
B. Invertebrate Reproductive Systems
C. Vertebrate Reproductive Systems
D. Male Reproductive System
E. Female Reproductive System
.
HOUR 3 5.5.
Endocrine Events that
Orchestrate Reproduction
A. Hormonal Control of
Timing of Reproductive
Cycles
B. Gonadal Steroids and
Their Control
C. Menstrual Cycle
D. Hormones of Human
Pregnancy and Birth
E. Multiple Births
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
ADVANCED CLASS QUESTIONS:
1. About one-half of a herd of cattle is born male, but a farmer does not want all these troublesome tough-meat
bulls. Therefore, most are castrated before puberty. What physiological and body changes would you expect,
and would the steer resemble the cow or bull and why?
2. Twinning rates vary around the earth, with twins occurring in one out of 80 births in the U.S., with higher
frequency in the tropics where life-span is much shorter, and with less frequency in northern regions and Asia
where life-span has historically been longer. Age of first menstruation is also lower in the tropics, higher in
Norway, etc. What are the physiological basis and the evolutionary implications of this?
3. If some reptiles (e.g. garter snakes) hold eggs internally until they hatch, why has this strategy not evolved in all
snakes?
4. Why would you predict hormonal rather than nervous control of the reproductive cycle?
5. Why would a woman who was having difficulty conceiving due to too low hormone levels be more likely to
have multiple births when treated?
6. How might some mechanisms triggering contractions cause too early a delivery when a mother is carrying
multiples?
7. Why would evolution not select for triggering milk production in humans based simply on a clock-like
mechanism that “went off” at nine months?
Twelfth Edition Changes
1.
2.
3.
4.
5.
6.
Most changes are relatively minor:
Few birds have a true penis (exceptions are Ostrich and the Argentine Lake Duck).
The oocyte remains viable for approximately 12 hours.
Progesterone—only contraceptives (“mini pill,” Depo-Provera, Norplant) may not block follicular
development or ovulation. Rather, they act on the reproductive tract as a whole, making it inhospitable for
sperma and any fertilized oocyte.
Secretion of Oxytocin during childbirth is another example of positive feedback.
The production of new life provides an opportunity for evolution to occur.
Revised figures include those illustrating sperm formation (Figure 5.8); sperm diversity (Figure 5.9); male
gonad anatomy (Figure 5.12); and female gonad anatomy (Figure 5.13).
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Source Materials
[Bold = recommended; for vendor abbreviations, see list of distributors in Appendix 1]
After Pregnancy (HE), 30-min. video
Beginning of Life (PYR), 26-min. film
Biology–Endocrine Control: Systems in Balance (A-CPB), 30-min. video
Body Atlas: In the Womb (AVP) (JLM), 30-min. video
Body Atlas: Sex (AVP) (JLM), 30-min. video
Breastfeeding (Q), Win CD
Coming Together (FH), 28-min. video
Comprehensive Review in Biology: Reproduction, Growth and Development (Q), Mac, Win
Condyloma (HE), 7-13-min. video
Control In Reproduction (Biology: Form and Function) (A-CPB), 24-min. video
Cycles of Life: Exploring Biology–Animal Reproduction and Development (A-CPB), 30-min. video
Differences Between Men and Women (FH), 23-min. video
Dilation and Curettage (HE), 7-13-min. video
The Drama of Reproduction (WARDS), 15-min. video
The Drama of Reproduction (VWR), 51-min. video
Dysmenorrhea (HE), 7-13-min. video
Endometriosis (HE), 7-13-min. video
Fibroids (HE), 7-13-min. video
Gender and Reproduction Series (CBSC), 12 25-min. videos
Growing Old in a New Age–Love, Intimacy and Sexuality (A-CPB), 1-hr. video
How Life Begins (CRM), 46-min. video
Human Body Series: Reproductive System (PHO), 14-min. video
Human Physiology: Male and Female Reproductive Systems (CBSC), 23-min. filmstrip
Human Reproduction (CRM), 22-min. video
Hysterectomy (HE), 7-13-min. video
Hysterectoscopy (HE), 7-13-min. video
Infertility (HE), 30-min. video
Infertility and Adoption (UC), 24-min. video
Infertility: New Treatments (FH), 25-min. video
Infertility Overview (HE), 7-13-min. video
Into the World (FH), 28-min. or video
Introduction to General Biology: The Human Body II (Q), Mac, DOS
Laparoscopy (HE), 7-13-min. video
Life in the Womb (HRM), filmstrip or video
Lifetimes of Change: Development and Growth (AIMS), 17-min. video, laserdisc
The Male and The Female (IM), 29-min. video
The Meiotic Mix (FH), 10-min. video
Men, Women, and the Sex Difference: Boys and Girls are Different (FH), 43-min. video
Menopause (HE), 30-min. video
Menopause and Osteoporosis (HE), 7-13-min. video
Menopause: A Woman's Quest for Answers (UC), 60-min. video
Menstruation (HE), 30-min. video
The Miracle of Birth (AIMS), 30-min. video, laserdisc
The Nature of Sex (IM), 6 60-min. videos
A New Life (FH), 28-min. video
NOVA: The Miracle of Life (FISH) (JLM) (MBI) (SK&BL) (WGBH), 57-min. video
NOVA: Secret of the Sexes (PLP), 57-min. video
NOVA: The Truth About Impotence (WGBH), 60-min. video
NOVA: What's New About Menopause? (MBI) (NEB) (WGBH), 60-min. video
Pap Abnormal (HE), 7-13-min. video
Partners With Your Doctor—Men (HE), 9-min. video
Pregnancy (HE), 30-min. video
Premenstrual Syndrome (HE), 7-13-min. video
Reproduction and Meiosis (IM), 29-min. video
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Reproduction: A New Life (FH, PYR), 26-min. video
Reproduction: Coming Together (FH), 26-min. video
Reproduction in Organisms (AIMS) (JLM), 16-min. video, laserdisc
Reproduction: Into the World (FH), 26-min. video
Reproduction: Shares in the Future (FH), 26-min. video
Reproductive System (PLP), MS-DOS or CD
Reproductive Systems (IM) (NGS), 20-min. video
Reproductive System and Its Function (ei), slides or filmstrip
Science and Human Values: World of the Unborn (H&R), 30-min. video
Shares in the Future (FH), 26-min. video
Ultrascience: Sex Appeal (AVP), 30-min. video
Understanding Breast Cancer (Q), Mac, Win CD
Understanding Human Reproduction (HRM), filmstrip
Understanding Prostate Disorders (Q), Mac, Win CD
Urinary System and Reproductive Systems (PLP), Apple, CD, Mac
Urinary Tract Infections (HE), 7-13-min. video
Vaginitis (HE), 7-13-min. video
The Videodisc Encyclopedia of Medical Images. (FH) videodisc
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
CHAPTER
6
PRINCIPLES OF DEVELOPMENT
CHAPTER OUTLINE
6.1.
6.2.
History
A. Primary Organizer
1. Hans Spemann’s Research
a. Research in 1920-1930s centered on discovering how one tissue influenced the fate of
another: induction.
b. In 1916, Hans Spemann noted the capacity of tissue from the dorsal lip of the gastrulatransformed tissue it touched.
c. Repeated delicate experiments in 1921-1922 showed it induced a secondary embryo.
d. Dorsal lip tissue was considered the primary organizer that set the axis of the secondary
embryo.
e. His work set the stage for embryology breakthroughs after World War II.
f. Recent advances in molecular biology have inaugurated the second golden age of
embryology.
g. Secretion of certain molecules trigger or repress the activity of a combination of genes in
nearby cells.
h. Cells of the Spemann organizer secrete proteins such as Noggin, Chordin, and Follistatin.
i. Similar proteins occur in both invertebrates and vertebrates.
j. These scientific breakthroughs ushered in the new science of Evolutionary Developmental
Biology.
2. All of the knowledge for constructing a complex egg must be in the nucleus and cytoplasm.
3. Genetics and molecular biology techniques have made a breakthrough in embryology in the last
two decades.
B. Early Concepts: Preformation Versus Epigenesis
1. Preformation is the concept of a miniature adult being present in the sperm or egg, waiting to
unfold.
a. Some claimed they could see a miniature adult in the egg or sperm. (Figure 6.1)
b. A young animal is merely unfolding the structures that are already there.
2. In 1759, Kaspar Friederich Wolff showed there was no preformed chick in the early egg.
a. Undifferentiated granular material became arranged into layers.
b. The layers thickened, thinned, and folded to produce the embryo.
c. Epigenesis is the concept that the embryo contains building materials that are assembled.
3. Development is a series of progressive changes. (Figure 6.2)
a. This begins when a fertilized egg divides mitotically.
b. Specialization occurs as a hierarchy of developmental “decisions.”
c. Cell types do not unfold but arise from conditions created in preceding stages.
d. Interactions become increasingly restrictive; each stage limits developmental fate.
e. With each new stage, cells lose the option to become something different–it becomes
determined.
f. Both cytoplasmic localization and induction cause this feature.
Fertilization
A. Initial Event
1. Fertilization is the union of male and female gametes.
a. Fertilization provides for recombination of paternal and maternal genes, restoring the diploid
number.
b. Fertilization activates the egg to begin development.
B. Oocyte Maturation
1. Contrast with sperm.
a. The sperm eliminates nearly all cytoplasm and condenses its nucleus.
b. The egg grows in size by accumulating yolk; it also contains much mRNA, ribosomes, tRNA
and elements for protein synthesis.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
6.3.
2. Morphogenetic determinants direct the activation and repression of specific genes in the egg.
3. The egg nucleus grows in size, bloated with RNA and is called the germinal vesicle.
4. Preparations in the egg occur during the prolonged prophase.
5. After meiosis resumes, the egg is ready to fuse its nucleus with the sperm nucleus.
C. Fertilization and Activation
1. A century of research has been conducted on marine invertebrates, especially sea urchins.
2. Contact and Recognition Between Egg and Sperm (Figures 6.3, 6.4)
a. Marine organisms release enormous numbers of sperm in the ocean to fertilize eggs.
b. Many marine eggs release a chemotactic molecule to attract sperm of the same species.
c. Sea urchin sperm first penetrate the jelly layer before contacting the vitelline envelope.
d. Egg-recognition proteins on the acrosomal process bind to species-specific sperm receptors on
the vitelline envelope.
e. In the marine environment, many species may be spawning at the same time.
f. Similar recognition proteins are found on sperm of vertebrate species.
3. Prevention of Polyspermy
a. A fertilization cone forms where the sperm contacts the vitelline membrane. (Figure 6.5)
b. Important changes in the egg surface block entrance to any additional sperm.
c. Polyspermy, the entry of more than one sperm, would cause a triploid nucleus.
d. In the sea urchin, an electrical potential rapidly spreads across the membrane; this is the “fast
block.”
e. This is followed by the cortical reaction.
1) Thousands of enzyme-rich cortical granules below the egg membrane fuse with the
membrane.
2) The cortical granules release contents between the membrane and vitelline envelope.
3) This lifts the envelope and forms a moat.
4) One cortical granule enzyme causes the vitelline envelope to harden, becoming the
fertilization membrane. (Figure 6.6)
4. Fusion of Pronuclei and Egg Activation
a. After sperm and egg membranes have fused, the sperm disconnects from its flagellum.
b. The enlarged sperm nucleus is the male pronucleus and migrates inward to contact the
female pronucleus.
c. Fusion forms a diploid nucleus.
1) Nuclear fission takes 12 minutes in sea urchins; about 12 hours in mammals.
2) The fertilized egg is now properly called a zygote.
d. Fission removes one or more inhibitors that blocked metabolism and kept the egg quiescent.
e. DNA and protein synthesis undergoes a burst of activity, using a supply of mRNA in the egg
cytoplasm.
f. Fertilization initiates reorganization of cytoplasm and repositions determinants that begin
development and cleavage.
Cleavage and Early Development
A. Blastomeres
1. The embryo undergoes cleavage to convert the large cytoplasmic mass into small maneuverable
cells.
2. No cell growth occurs, only subdivision until cells reach regular somatic cell size.
3. At the end of cleavage, polychaete worms have 1000 cells, amphioxus has 9000, and frogs have
700,000.
4. Polarity—a polar axis—establishes the direction of cleavage and differentiation.
B. Patterns of Cleavage (Figure 6.7)
1. The pattern of cleavage is affected by
a. quantity and distribution of yolk present, and
b. genes controlling the symmetry of cleavage.
2. There are four principal types of cleavage.
C. Amount and Distribution of Yolk Affects Cleavage
1. Isolecithal yolk describes eggs with very little yolk and the yolk is distributed evenly.
a. In such eggs, cleavage is holoblastic.
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Copyright © 2005 – The McGraw-Hill Companies srl
b.
c.
The cleavage furrow extends completely through the egg.
Isolecithal eggs are widespread and seen in: echinoderms, tunicates, cephalochordates,
molluscs and mammals.
d. Cleavage is slowed in the yolk-rich vegetal pole.
2. Mesolecithal eggs have a moderate amount of yolk concentrated in the vegetal pole.
a. The animal pole is opposite the vegetal pole and contains cytoplasm and very little yolk.
b. These eggs cleave holoblastically, but cleavage is retarded in yolk-rich vegetal pole.
c. The cleavage furrow progresses much more slowly through the vegetal pole; thus cleavage is
faster in the animal region.
d. Amphibians have mesolecithal eggs.
3. Telolecithal eggs have much yolk concentrated at the vegetal pole.
a. Actively dividing cytoplasm is confined to a narrow disc-shaped mass on the yolk.
b. Cleavage is partial or meroblastic; the furrow does not cut through the heavy yolk.
c. Birds, reptiles, most fishes and a few amphibians have telolecithal eggs.
4. Centrolecithal eggs have a large mass of centrally located yolk.
a. Cytoplasmic cleavage is limited to a surface layer of yolk-free cytoplasm; yolk-rich inner
cytoplasm is uncleaved.
b. They have meroblastic cleavage. (Figure 6.8)
c. Insects and many other arthropods have centrolecithal eggs.
d. Yolk is therefore an impediment to cleavage.
D. Amount of Yolk Affects Developmental Mode
1. In most animals, a mother does not directly nourish embryonic development but has provisioned
the egg with yolk.
2. The amount of yolk is related not only to cleavage patern, but also to whether a larval stage occurs
during development.
3. Animals in which the zygote is telolecithal generally have direct development.
4. Species with isolecithal or mesolecithal zygotes generally have indirect development.
5. In direct development is characteristic of animals where the larval stage is between embryo and
adult.
a. Metamorphosis is a change from larval to adult body form.
b. Mammalian zygotes bypass the larval stage.
c. A placental attachment to the mother provides ongoing nourishment.
6. Direct development can occur when there is enough yolk to support growth as juveniles; this
occurs in reptiles and birds.
E. Cleavage Affected by Different Inherited Patterns
1. Different cleavage patterns are characteristic of different phylogenetic lineages.
2. Isolecithal eggs demonstrate four major patterns.
3. Radial Cleavage
a. Embryonic cells are arranged in a radial symmetry around the animal-vegetal axis.
b. In sea stars, cleavage begins by two identical daughter cells cut through the animal vegetal
axis.
c. The next cleavage runs parallel to the animal vegetal axis and cuts the blastomeres in half.
d. The next cleavage is perpendicular to the animal vegetal axis and forms two tiers of 4 cells
each.
e. Amphibian embryos have similar cleavage with slower furrowing in the yolk region.
f. Radial cleavage is characteristic of the Deuterostomia, including echinoderms, hemichordates
and chordates.
4. Spiral Cleavage
a. Spiral cleavage proceeds in a sequence oblique to the animal-vegetal axis.
b. Cells produced pack tightly in the adjacent furrows, like soap bubbles.
c. Spiral cleavage is found in annelids, nemerteans, turbellarians, all molluscs except
cephalopods, some brachiopods, echiurans and some other Prostomia. (Figure 6.9)
5. Bilateral Cleavage
a. Prior to fertilization, the egg is defined by unequal cytoplasmic components. (Figure 6.10)
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Copyright © 2005 – The McGraw-Hill Companies srl
b.
The first cleavage furrow passes through the animal vegetal axis dividing the asymmetrically
divided cytoplasm between the two blastomeres.
c. This first cleavage pattern determines the future right and left side.
d. The half-embryo formed on one side is the mirror image of the half embryo on the other side.
e. Ascidians (tunicates) demonstrate this cleavage pattern.
6. Rotational Cleavage
a. The first cleavage plane is aligned with the animal vegetal axis.
b. However, in the second cleavage, one blastomere divides meridionally while the other divides
equatorially, rotated 90 degrees to the first.
c. Early divisions may be asynchronous and possess odd numbers of cells below the 2-4-8-16...
series that would occur with synchronous division.
d. After the third division, cells form a tightly packed cluster stabilized by outer cells with tight
junctions, the trophoblast.
e. The trophoblast will form the embryonic portion of the placenta.
f. Cells that give rise to the embryo are the inner cell mass.
g. This type of cleavage is present in mammals and is slower than in other animal groups.
7. Discoidal Cleavage
a. Telolecithal eggs divide by discoidal cleavage.
b. There is a large mass of yolk in each egg; cleavage is confined to a small disc of cytoplasm.
c. Early cleavage furrows carve the disc into a single layer of cells called the blastoderm.
8. Superficial Cleavage
a. The centrally located mass of yolk restricts cleavage to the cytoplasmic rim of the egg.
b. Cytoplasmic cleavage does not occur until many rounds of nuclear division.
c. Eight rounds of mitosis produce 256 nuclei that migrate to the yolk-free periphery.
d. Some nuclei at the poles form pole cells; they give rise to germ cells of the adults.
e. The entire egg cell membrane enfolds to partition each nucleus and form a layer of cells.
F. Blastulation (Figure 6.11)
1. The blastula is the resulting cluster of cells regardless of cleavage pattern.
a. In mammals, this is called the blastocyst.
b. Often, cells arrange themselves around a central fluid-filled blastocoel.
c. At this stage, cell number ranges from a few hundred to several thousand.
d. The embryo has not increased in size beyond the size of the zygote, but each nucleus has a
full set of DNA.
G. Gastrulation and the Formation of Germ Layers
1. Gastrulation converts the spherical blastula into a complex structure with three layers.
a. Ectoderm covers the embryo.
b. Mesoderm and endoderm are on the interior.
c. The new positions and cell neighbors establish the embryonic body plan.
2. Patterns of gastrulation vary enormously depending on the amount of yolk.
a. The yolk impedes gastrulation.
b. Gastrulation is simple in non-yolky embryos, complex in yolk-laden eggs.
3. Sea Star Gastrulation
a. Gastrulation begins with vegetal area flattening to form the vegetal plate.
b. Invagination is a bending inward of the vegetal plate one-third into the blastocoel.
c. The archenteron is the new cavity formed by this invagination.
d. The archenteron is the primitive gut; the blastopore is the opening to the outside.
e. In deuterostomia, the blastopore becomes the anus, and the mouth forms secondarily.
f. The archenteron elongates toward the animal pole and expands into two pouch-like coelomic
vesicles.
4. Germ Layers
a. The outer ectoderm will give rise to epithelium and the nervous system.
b. The endoderm gives rise to the epithelial lining of the digestive tube.
c. The mesoderm will form the muscular system, reproductive system, peritoneum and the sea
star’s endoskeleton and water-vascular system.
5. Gastrulation in Prostomia
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a.
b.
6.4.
The blastopore becomes the mouth and the anus forms secondarily.
The mesoderm forms differently, arising from the lip of the blastopore and proliferating
between the walls of the archenteron and outer body wall.
c. These mesodermal precursors arise from the large 4d cell at the 29 to 64 cell stage.
6. Radial Cleavage in Deuterostomes
a. Gastrulation is influenced by the mass of inert yolk in the vegetal half of the embryo.
b. It begins in the marginal zone of the blastula where the animal and vegetal hemispheres meet
with less yolk.
c. Sheets of cells in the marginal zone turn inward over the blastopore lip and move inside to
form mesoderm and endoderm.
7. The Primitive Streak (Figure 6.12)
a. The primitive streak forms the anterioposterior axis and center of early growth in bird and
reptile embryos.
b. The blastoderm consists of two layers: epiblast and hypoblast with a blastocoel between them.
c. The epiblast sheet moves toward the primitive streak and over the edge, migrating as cells
into the blastocoel.
d. One stream of cells moves deeper, displacing midline hypoblast, and forms endoderm.
e. Surface cells form ectoderm.
f. All three layers lift from the yolk and pinch off, leaving a stalk attachment to the yolk at
midbody.
8. Mammalian Gastrulation
a. Epiblast cells move medially through the primitive streak into the blastocoel; cells migrate
laterally through the blastocoel to form mesoderm and endoderm.
b. Endoderm derived from the hypoblast forms a yolk sac without yolk; mammals utilize
nutrients from a placenta.
c. Reptiles, birds and mammals share a common ancestor whose eggs were telolecithal; all
inherited this gastrulation pattern and mammals then evolved isolecithal eggs with a
telolecithal pattern.
9. Two versus Three Germ Layers
a. Cnidaria and Ctenophora have only two germ layers (endoderm and ectoderm) and are
diploblastic.
b. Other metazoa have three germ layers and are triploblastic.
H. Formation of the Coelom (Figure 6.13)
1. The coelom is a true body cavity that contains the viscera; it is formed in one of two methods.
a. Schizocoelous formation forms the coelom from splitting of mesodermal bands originating
from blastopore region and growth between ectoderm and endoderm.
b. Enterocoelous formation forms the coelom from pouches of the archenteron.
c. Protostomes develop by the schizocoelous method.
d. Deuterostomes, except for vertebrates, follow the enterocoelous plan.
e. Vertebrates form a coelom by schizocoelous formation; this evolved anew to accommodate
large stores of yolk.
Mechanisms of Development
A. Nuclear Equivalence
1. Roux-Weismann Hypothesis
a. An early—but wrong—explanation of differentiation was based on division of nuclear
material along the cell lineage.
b. Early embryologists saw this as an explanation of differentiation; hereditary material was
parceled out to cells.
c. Hans Driesch separated the two-celled sea urchin stage; both developed into normal larvae but
this did not disprove eventual progressive modification.
2. Hans Spemann Disproves Roux-Weismann Hypothesis, Discovers Gray Crescent
a. Spemann used human hair to almost tie-off a salamander zygote.
b. The nucleus was on one side; only cytoplasm on the other.
c. The nucleated side divided many times: only when one nucleus wandered across did the
cytoplasmic side divide.
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d.
Its normal development showed no nuclear material had been lost after many nuclear
divisions.
e. Occasionally the nucleated side only developed into a ball of “belly” tissue; it was missing the
pigment-free gray crescent area that appears at fertilization.
e. This disproved the Roux-Weismann Hypothesis and showed that cytoplasm in the gray
crescent contained essential information.
f. Spemann’s experiment demonstrated that every blastomeres contains sufficient genetic
information for the development of a complete animal.
g. Cloning is still technically difficult.
3. Methods of Differential Cell Differentiation
a. Except for insects, cells become committed to particular fates from cytoplasmic segregation
of determinative molecules during cleavage, and from interaction among neighboring cells
(induction).
B. Cytoplasmic Specification
1. Cytoplasmic components are unevenly distributed in a zygote.
2. Different components contain morphogenetic determinants that control commitment to cell type.
3. Different determinants are partitioned among different blastomeres by cleavage and determine cell
fate.
4. Some tunicate species have different colored types of cytoplasm.
a. Yellow cytoplasm gives rise to muscle cells.
b. Gray equatorial cytoplasm produces the notochord and neural tube.
c. Clear cytoplasm produces larval epidermis.
d. Gray vegetal cytoplasm gives rise to the gut.
5. In this process, cell fate is determined without reference to neighboring cells.
a. An isolated blastomere still forms characteristic structures.
b. Absence of a blastomere results in absence of specific structures it would have formed.
c. Mosaic development refers to this pattern of development and is found in most protostomes.
(Figure 6.14)
6. In many animals, fate of a cell depends on interactions with neighboring cells.
a. In these embryos, each early cell alone can produce an entire embryo if separated.
b. The early blastomere has the ability to follow more than one path of differentiation.
c. If a blastomere is removed, the remaining blastomeres can alter their normal fates to
compensate.
d. This adaptability is regulative development and occurs in most deuterostomes except
tunicates.
C. Embryonic Induction (Figure 6.15)
1. Induction is the capacity of some cells to evoke a specific developmental response in other cells.
a. Following Hans Spemann’s work described before, a graft of the dorsal blastopore lip could
induce host ectoderm to form a neural tube.
b. Such a graft is formed of partly grafted tissue and partly induced host tissue.
c. But only grafts of dorsal lip blastopore tissue could cause induction.
d. Only ectoderm of the host would respond by developing nervous tissue.
e. Dorsal lip was the primary organizer because it was the only tissue to induce growth.
f. Spemann called this primary induction the first inductive event; there are other cell types that
originate from secondary induction.
2. Cells that have differentiated act as inductors for adjacent undifferentiated cells.
a. Timing is critical; primary induction sets in motion secondary induction.
b. The sequence includes cell movement, changes in adhesion, and cell proliferation.
c. There is no “hard-wired” master control panel directing development.
D. Gene Expression During Development
1. After fertilization, proteins are translated from stored mRNA transcribed from maternal genome.
2. In many animals, maternal mRNA directs protein synthesis through cleavage and to mid-blastula
stage.
3. After this, protein synthesis switches from maternal to zygotic control as the nucleus transcribes
its own mRNA.
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4.
6.5.
Homeotic Genes
a. Gene expression is regulated to ensure orderly development.
b. Mutations of homeotic genes in fruit flies revealed they controlled overall body plan of legs,
wings, etc.
c. The homeobox is a 180-nucleotide DNA sequence that occurs in most animals.
d. These are master genes that control expression of subordinate genes.
e. Homeotic genes are remarkably similar across diverse species; evolution “solved” the
development problem only once.
f. Proteins coded by homeobox genes contain a highly conserved 60-amino acid sequence: the
homeodomain.
g. The homeodomain proteins all bind to specific promoter sequences of DNA; they switch
subordinate genes on or off.
h. Mice and humans have four clusters of homeobox-containing genes on separate
chromosomes; all are homologues of the fruit fly’s homeotic genes.
5. Homeobox complexes are primitive.
a. Their universal existence across phyla indicates they were present in a common metazoan
ancestor.
b. Their function was to specify the fundamental anterior-posterior axis.
c. Once complex animals evolved, it could be modified to produce major new body plans.
Vertebrate Development
A. Common Vertebrate Heritage (Figures 6.16-6.19)
1. One outcome of shared ancestry in vertebrates is the similarity of postgastrula embryos.
a. For a short time, all vertebrate embryos share: dorsal neural tube, notochord, pharyngeal gill
pouches with aortic arches, ventral heart and postanal tail.
b. This similarity is extraordinary considering the variety of eggs and developmental patterns.
B. Amniotes and the Amniotic Egg (Figure 6.20)
1. Amniotes are a monophyletic grouping of vertebrates.
a. Their embryos develop within the amnion, a membranous sac that provides an aquatic
environment and protects it from shock.
b. The amniotic egg contains four extraembryonic membranes including the amnion.
c. The amniotic egg allowed development away from water.
d. The yolk sac is the first membrane and pre-dates the amniotes by millions of years; it is
extraembryonic and is discarded.
e. The allantois is a sac that grows out of the hindgut and holds metabolic wastes during
development.
f. The chorion lies beneath the eggshell and encloses the rest of the embryo.
g. With growth, the allantois and chorion fuse to form the chorioallantoic membrane, a
provisional “lung.”
h. Evolution of the shelled amniotic egg made fertilization a requirement before a shell was
developed.
C. Mammalian Placenta and Early Mammalian Development
1. Mammals inherited the amniotic egg but retained it in the mother’s body.
a. Monotremes are examples of primitive mammals that lay eggs.
b. In marsupials, embryos develop but do not “take root” in the uterus; they climb out and enter
an external abdominal pouch.
2. Placental mammals represent 94% of the Class Mammalia.
a. Evolution of a placenta required considerable restructuring.
b. Extraembryonic membranes had to restructure to form the placenta.
c. The maternal oviduct had to evolve to develop a uterus to house the embryo.
3. Early Stages of Mammalian Development (Figure 6.21)
a. The blastocyst travels down the oviduct toward the uterus, propelled by ciliary action and
peristalsis. (Figure 6.22)
b. At about the sixth day, the human blastocyst composed of about 100 cells contacts the
endometrium.
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c.
6.6.
On contact, the trophoblast cells proliferate rapidly and produce enzymes to break down
epithelium of the endometrium.
d. By the twelfth day, the blastocyst is totally buried, surrounded by maternal blood.
e. The trophoblast thickens, sending out tiny fingers of chorionic villi.
f. The surface area of chorionic villi eventually expands to 13 square meters in the human
placenta.
g. The amnion remains unchanged; the embryo floats in this “pond.”
h. The yolk sac contains no yolk but has stem cells that give rise to blood and lymphoid cells;
they later migrate into the developing embryo. (Figure 6.23)
i. The allantois is not needed to store wastes; it contributes to the umbilical cord.
j. The chorion forms the embryo’s side of the placenta.
k. The germinal period is the first two weeks.
l. The embryonic period includes the next eight weeks when all major organs and body shape
form; this is a period that is sensitive to drugs that may cause malformation in the embryo.
m. The fetal period begins when embryo becomes a fetus at about two months; mainly a growth
phase, but the endocrine and nervous systems still develop.
Development of Systems and Organs (Figure 6.24)
A. Germ Layers
1. Germ layers should not be confused with germ cells (eggs and sperm).
2. Germ layers do not alone determine differentiation but rather the position of embryonic cells.
B. Derivatives of Ectoderm: Nervous System and Nerve Growth (Figure 6.25)
1. Just above the notochord, the ectoderm thickens to form a neural plate.
2. Edges of the neural plate fold up to create an elongated, hollow neural tube.
a. The anterior end of neural tube enlarges and forms the brain and cranial nerves.
b. The posterior end forms the spinal cord and spinal motor nerves.
c. Neural crest cells pinch off from the neural tube.
3. Neural crest cells form many structures.
a. They become portions of cranial nerves, pigment cells, cartilage, bone, ganglia of the
autonomic system, medulla of the adrenal gland, and parts of other endocrine glands.
b. It is unique to vertebrates and was important in evolution of the vertebrate head and jaws.
4. In 1907, Ross Harrison cultured nerve cells; each axon grows from one cell.
5. Additional research revealed that a nerve axon grows in response to guidance molecules secreted
into its path. (Figure 6.26)
C. Derivatives of Endoderm: Digestive Tube and Survival of Gill Arches
1. During gastrulation, the archenteron forms as the primitive gut.
2. This endodermal cavity eventually produces the digestive tract, lining of pharynx and lungs, most
of the liver and pancreas, thyroid and parathyroid glands and thymus.
3. The alimentary canal develops from primitive gut; ends are lined with ectoderm.
4. Lungs, liver and pancreas arise from the foregut.
5. During development, endodermally-lined pharyngeal pouches interact with overlying ectoderm to
form gill arches.
6. In fish, gill arches become gills.
7. Gill arches remain as necessary primordia for a variety of other structures in terrestrial vertebrates.
a. The first arch and its endoderm-lined pouch form the upper and lower jaws.
b. Second, third and fourth gill pouches become the tonsils, parathyroids and thymus.
c. The original function has been abandoned but the structure is retained for new purposes; this
provides a view of evolutionary history.
D. Derivatives of Mesoderm: Support, Movement and the Beating Heart
1. With an increase in size and complexity, mesodermally derived structures take up a greater
proportion.
2. Muscles arise from mesoderm along each side of the neural tube.
a. The mesoderm divides into a linear series of somites (38 in humans).
b. The splitting, fusion and migration of somites produce the:
1) axial skeleton,
2) dermis of dorsal skin, and
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3.
3) muscles of the back, body wall and limbs.
c. Limbs begin as buds from the side of the body; projections become fingers and toes.
Mesoderm gives rise to the embryonic heart.
a. Guided by underlying endoderm, two clusters of precardiac mesodermal cells move to either
side of the gut.
b. These clusters differentiate into a pair of double-walled tubes that fuse into a single thin tube.
c. The primitive heart begins beating on the second day of the 21-day incubation period; there
are no blood or vessels at this time.
d. Twitching becomes rhythmical as the ventricle and atrium develops; each chamber has a
faster intrinsic beat.
e. A specialized sinoatrial node in the sinus venosus eventually takes charge as pacemaker.
f. The circulatory system becomes critical to deliver food from the yolk and return wastes to
extraembryonic tissues.
Lecture Enrichment
1.
2.
3.
4.
5.
Describe how cellular differentiation occurs as different genes are turned on and off, and how different proteins
and enzymatic products are produced in the different types of cells. Most of biology can be reduced to protein
chemistry, and development is change in that chemistry.
In explaining various kinds of differentiation and how dissimilar cells could come from a single zygote, a visual
image of animal phylogeny is useful to show the evolution of cleavage patterns, etc.
A balloon can be pinched many times to illustrate how the cleavage process can go through many rounds of cell
division with no cell growth, starting with the egg as the largest single cell in a species. Emphasize that
differentiation may begin with the first cell division.
Keep students aware that a chick embryo has requirements other than the nutrients in the yolk. Ask what they
are and how they are dealt with—such as oxygen requirements (enters the shell) and removal of wastes
(accumulate as uric acid in an extraembryonic membrane and are discarded with the eggshell).
Amniotic fluid is used to examine a fetus for genetic defects, since cells of the fetus are shed from the skin and
from the respiratory and urinary tracts into the fluid. Chorionic villi are one of the first fetal tissues that can be
sampled in prenatal diagnosis.
Commentary/Lesson Plan
Background: Most students will have virtually no direct experiences with embryology beyond general biology
abstractions. A few students may have seen fertilized eggs and recognized that development occurs on the surface
of the yolk. Developmental biology is rapidly expanding and modifying its knowledge base, perhaps second only to
our rapidly expanding understanding about the brain and nervous system. Some of this chapter is critical to
citizenry understanding future controversies concerning use of fetal tissues, etc. The complexities of developmental
biology research likewise will require using visuals. The history story line (Spemann et al.) may be an excellent
way to carry the otherwise abstract and complex topic.
Misconceptions: Some students may have been led to believe that there is some point in development that is the
“beginning of life”; since the germ line is continuous and living from sperm/egg through zygote, this is a nonbiological question and relates to when society assigns personhood. Since it is not usually stated otherwise, there is
the assumption that all cells in the zygote become the embryo and then the born organism. As the text makes clear,
many of the cells at the early 64-cell stage become placenta which has to proliferate rapidly to become part of the
support system for the developing embryo.
Schedule: If extensive history illustrations are used, add an additional class period.
HOUR 1 6.1.
6.2.
History
A. Primary Organizer
B. Early Concepts: Preformation
Versus Epigenesis
Fertilization
A. Initial Event
B. Oocyte Maturation
C. Fertilization and Activation
6.3.
Cleavage and Early Development
A. Blastomeres
B. Patterns of Cleavage
C. Amount and Distribution of Yolk
Affects Cleavage
D. Amount of Yolk Affects
Developmental Mode
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HOUR 2 6.4.
6.5.
E. Cleavage Affected by Different
Inherited Patterns
F. Blastulation
HOUR 3
G. Gastrulation and the Formation of
Germ Layers
6.6.
H. Formation of the Coelom
Mechanisms of Development
A. Nuclear Equivalence
B. Cytoplasmic Specification
C. Embryonic Induction
D. Gene Expression During
Development
Vertebrate Development
A. Common Vertebrate Heritage
B. Amniotes and the Amniotic Egg
C. Mammalian Placenta and Early
Mammalian Development
Development of Systems and Organs
A. Germ Layers
B. Derivatives of Ectoderm: Nervous
System and Nerve Growth
C. Derivatives of Endoderm:
Digestive Tube and Survival of Gill
Arches
D. Derivatives of Mesoderm: Support,
Movement and Beating Heart
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ADVANCED CLASS QUESTIONS:
1. In a classic experiment in the 1980s, the cells of three mouse embryos were intermingled at the 8-64 cell stage;
they cluster and become one mouse called a chimera with different parts showing the features of its six different
parents! What does this indicate relative to the independence of one individual cell as the smallest unit of life?
When researchers intermingled the cells of four or five embryos, only traits from three parental lineages were
expressed in the chimera. Why? Why would the distribution of mouse embryo-versus-placenta cells not be 5050 or even less for the placenta?
2. In a rural hospital in Eastern Europe, a mother with type O blood gave birth to her biological child with type AB
blood. Based on genetics, this is impossible. A check of her parents revealed she was a chimera, a fusion of
two different sibling embryos that developed as one individual but with two tissue types. Her husband had type
B blood. What are her two tissue types? How does embryology place a caveat on the mathematics of genetics
in paternity cases?
3. When an insect egg reproduces many nuclei without cytoplasmic cleavage, does this violate the cell theory?
4. Why do you inherit all of your mitochondria from your mother? [Careful: The sperm tail does enter the egg,
contrary to some textbooks, but carries far fewer mitochondria than egg mitochondria; they are “worn out” and
are marked for destruction.]
5. Combining information from both Chapters 8 and 9, why are “Siamese twins” joined? [The answer should
combine information about twinning, implantation, and developmental signals.]
6. Chemical signals are involved in development. Should these chemical signals be considered hormones? Why
or why not?
7. Discuss the genetics of pattern formation in embryogenesis. Be sure to include a discussion of morphogens
(both specific and general).
Twelfth Edition Changes: Numerous new changes in content have been incorporated.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Recent advances in molecular biology have inaugurated the second golden age of embryology.
Induction is due to the secretion of certain molecules that trigger or repress the activity of combinations of
genes in nearby cells.
Secreted inducing proteins have names such as Noggin, Chordin, and Follistatin, which allow nearby cells to
develop into the nervous system and other tissues along the middle of the back.
These new developments have given rise to the new field of evolutionary developmental biology.
Cleavage is slowed in the yolk-rich vegetal pole.
The amount of yolk is related not only to cleavage pattern, but also to whether a larval stage occurs during
development.
Animals in which the zygote is teleocithal generally have direct development into a small version of the adult.
In mesolecithal and telolecithal eggs with meroblastic cleavage there are two other major patterns: discoidal
and superficial.
Phyla with spiral cleavage are further restricted to one of the two clades within Protostomia, the
Lophotrochozoa.
The Gray Crescent is the precursor of the Spemann Organizer.
Spemann’s experiment demonstrated that every blastomeres contains sufficient genetic information for the
development of a complete animal.
Harmonious differentiation of tissues proceeds in three general stages: pattern formation, determination of
position in the body, and induction of limbs and organs appropriate for each postion. Each stage is guided by
morphogens. The structures appropriate to each segment are induced by homeotic genes, which are
characterized by a particular sequence of DNA, the homeobox. Mutations in homeotic genes result in the
development of inappropriate structure on a segment. Morphogens guide the development of limbs along three
body axes. Morphogens have been found in virtually all animals thoroughly examined to date.
Upgrades or new figures include the Spemann organizer (Figure 6.1); and developing chick wing (Figure 6.18).
80
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Source Materials [bold = recommended; for vendor abbreviations, see list of distributors in Appendix 1]
Amphibian Egg Development (IM) (JLM) 11-min. video
Amphibian Embryos (EBE), 16-min. video
Babymakers (CRM), 28-min. video
Beginnings of Life, The (PYR), 26-min. film
Bioethics Forums: Fetal Alcohol Syndrome (CAM), Mac, Win CD
Birth: Eight Women's Stories (FH), 70-min. video
Cell Differentiation: The Search for the Organizer (PHO) (IM), 15-min. video
Chemical Carcinogenesis: The Staging Theory (CRM), 28-min. video
Chick Embryo: Life Is Born (CRM), 20-min. video
The Chick Embryo: From Primitive Streak to Hatching (EBE), 43-min. video
Chick Embryology (NG), 12-min. film
A Child is Born (BFA), 22-min. video
Cloning: How and Why (SK&BL), 31-min. video
Cycles of Life: Exploring Biology–Animal Reproduction and Development (A-CPB), 30-min. video
David With Fetal Alcohol Syndrome (FH), 45-min. video
Death (FH), 23-min. video
Development and Aging (IM), 29-min. video
Developmental Biology (PHO) (IM), 19-min. video
Development of the Amphibian Embryo (VWR), 51-min. video
Development and Differentiation (CRM), 20-min. video
Development in Animals and Plants: It All Starts with DNA (GA), slides
Developmental Biology (PHO), 19-min. video
Diagnosis of Hidden Congenital Anomalies (MF), 10-min.
Embryology Illustrated Set 1–Early, Environmental and Body Cavity Malformations (O-BioMed), 76 slides
Embryology Illustrated Set 1I–The Brachial Apparatus, Head, Neck and Teeth (O-BioMed), 82 slides
Embryology Illustrated Set 1II–Heart and Respiratory Malformations (O-BioMed), 105 slides
Embryology Illustrated Set 1V–Digestive Malformations (O-BioMed), 85 slides
Embryology Illustrated Set V–The Urogenital System (O-BioMed), 79 slides
Embryology Illustrated Set V1–The Nervous System and Eye (O-BioMed), 90 slides
Embryology Illustrated Set VI1–The Musculoskeletal and Integumentary Systems (O-BioMed), 120 slides
Embryonic Organizers: Pathfinding in the Brain (IM), 25-min. video
Fetal Alcohol Syndrome and Other Drug Use During Pregnancy (FH), 36-min. video
Fetal Development: A Nine-Month Journey (AIMS), 14-min. laser videodisc
The Fish Embryo: From Fertilization to Hatching (EBE), 12-min. video
Fish Embryology (ESYO), 21-min. video
Generation Upon Generation [Ascent of Man Series] (AVP), 52-min. video
Growing Old in a New Age (A-CPB), 13 1-hr. videos
Hans Spemann (UC), 24-min. video
Hans Spemann and Embryonic Development (IM), 42-min. video
Heredity and Environment (CRM), 27-min. video
How Life Begins (CRM), 46-min. video
Human Physiology: Embryology (CBSC), 31-min. filmstrip
Human Reproduction (CRM), 20-min. video
In the Womb (IM), 25-min. video
Introduction to Development (IM), 22-min. video
Lifetimes of Change (AIMS), 17-min. laser videodisc
The Living Body: Aging (FH), 26-min. video
The Miracle of Birth (AIMS), 30-min. video, laserdisc
Morphogenesis: Shaping Up (IM), 24-min. video
A New Life (FH), 26-min. video
NOVA: Dr. Spock the Baby Doc (WGBH), 60-min. video
NOVA: How a Baby is Made (WGBH), 55-min. video
NOVA: Life's First Feelings (MBI) (NEB) (WGBH), 60-min. video
NOVA: The Miracle of Life (JLM) (FISH), 57-min. video
81
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
NOVA: Siamese Twins (MBI) (NEB) (WGBH), 60-min. video
NOVA: The Wonder of Life (NEB), 60-min. video
Pregnancy and You (Q), Mac, MS-DOS
Prenatal Development and Childbirth (PLP), Apple
Prenatal Developments (CRM), 23-min. video
Reproduction in Organisms (AIMS), 16-min. laser videodisc
Reproduction in the Sea Urchin (PHO), 13-min. video
Simple Beginnings? Child Development from Birth to Age Five (FH), 25-min. video
Small Miracles: Curing Fatal Conditions in the Womb (FH), 51-min. video
Ultrascience: Forever Young (AVP), 30-min. video [aging]
When Life Begins (CRM), 14-min. video
Whose Child Is This? (FH), 29-min. video
82
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
PART
III
DIVERSITY OF ANIMAL LIFE
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Architectural Pattern of an Animal.....................................
Classification and Phylogeny of Animals...........................
Protozoan Groups ...............................................................
Mesozoa and Parazoa .........................................................
Radiate Animals .................................................................
Acoelomate Animals ..........................................................
Pseudocoelomate Animals..................................................
Molluscs .............................................................................
Segmented Worms..............................................................
Arthropods..........................................................................
Aquatic Mandibulates.........................................................
Terrestrial Mandibulates.....................................................
Smaller Protostome Phyla................................................
Echinoderms and Hemichordates ...................................
Chordates............................................................................
Fishes..................................................................................
Early Tetrapods and Modern Amphibians..........................
Amniote Origins and Reptililan Groups .............................
Birds ...................................................................................
Mammals ............................................................................
83
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109
116
125
136
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155
163
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227
235
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257
____________________________________________________________________________________________
CHAPTER
7
ARCHITECTURAL PATTERN OF AN ANIMAL
CHAPTER OUTLINE
7.1.
7.2.
New Designs for Living
A. Levels of Organization in Organismal Complexity
1. Zoologists recognize 32 major phyla of living multicellular animals.
2. 500 million years ago in the Cambrian, nearly 100 phyla had evolved representing nearly all major
modern body plans.
3. Major body plans are the result of extensive selection and are a limiting determinant of future
adaptational variants.
4. Animals share structural complexities that reflect common ancestry.
Hierarchical Organization of Animal Complexity (Table 7.1)
A. Grades of Organization
1. Unicellular protozoan groups are the simplest animal-like organisms.
a. Within the cell, they perform all basic functions.
b. Diversity is achieved by varying architectural patterns of subcellular structures, organelles
and the whole cell.
2. Metazoa are multicellular animals.
a. Cells become specialized parts of a whole organism; these cells cannot live alone as do
protozoan cells.
b. Simplest metazoans show a cellular grade of organization and are not strongly associated to
perform a collective function.
3. More complex metazoans have a tissue grade organization with cells working closely together as
a unit.
4. Many tissues work together in an organ; most metazoans operate at the organ system level.
5. The chief functional cells of an organ are called parenchyma.
83
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
7.3.
B. Complexity and Body Size (Figure 7.1)
1. More complex grades of metazoan organization permit and promote evolution of large body size.
2. Surface-area-to-volume ratios have important consequences for animal respiration, heat, etc.
a. Surface area increases are the square of body length; volume is the cube of body length.
b. A large animal has less surface area compared to its volume than does a smaller animal.
c. Flattening or infolding the body increases surface area, as in flatworms.
d. Most animals had to develop internal transports systems to shuttle nutrients, gases and waste
products, as they became larger.
3. “Cope’s Law of Phyletic Increase” noted that lineages began with small individuals and
eventually evolved toward giant forms; it holds for nonflying vertebrates and many invertebrates.
(Figure 7.2)
4. Benefits of Being Large
a. Larger size buffers against environmental fluctuations in temperature, etc.
b. Size provides protection against predators and promotes offensive tactics.
c. Cost of maintaining body temperature is less per gram of weight in large than in small
animals.
d. Energy costs of moving a gram of body over a given distance are less for larger animals.
Extracellular Components of the Metazoan Body
A. Body fluids and extracellular structural elements are noncellular components of metazoan animals.
1. In contrast to intracellular fluids, extracellular fluids are outside the cells.
2. Blood plasma and interstitial fluid are part of the extracellular fluids in open and closed circulatory
systems.
B. Architectural Extracellular Structural Elements
1. Loose connective tissue is well-developed in vertebrates.
2. Cartilage is found in molluscs and chordates.
3. Bone is found in vertebrates.
4. Cuticle is pervasive in arthropods, nematodes, annelids and others.
C. Types of Tissues (Figure 7.3)
1. Histology is the study of types of tissues.
2. Epithelial Tissue (Figures 7.4, 7.5)
a. Epithelium is a sheet of cells that covers an internal or external surface.
b. It provides outside protection and internal linings, often modified to produce lubricants,
hormones or enzymes.
c. Simple epithelia are found in all metazoa.
d. Stratified epithelia are restricted to vertebrates.
e. All epithelia have an underlying basement membrane.
f. Blood vessels never penetrate epithelial tissues.
3. Connective Tissue (Figure 7.6)
a. Connective tissues are nearly everywhere in the body.
b. It is made up of few cells, many extracellular fibers and a ground substance or matrix.
c. In vertebrates, there are two types of connective tissue proper.
1) Loose connective tissue has fibers and both fixed and wandering cells in a syrupy matrix.
2) Dense connective tissues (e.g. ligaments and tendons) are characterized by densely
packed fibers.
d. Much fibrous tissue is made of protein collagen, the most abundant protein in the animal
kingdom.
e. Connective tissue also includes blood, lymph and tissue fluid.
f. Cartilage is semirigid connective tissue with closely packed fibers embedded in a gel-like
matrix.
g. Bone is calcified connective tissue with calcium salts organized around collagen fibers.
4. Muscular Tissue (Figure 7.7)
a. Muscle is the most abundant tissue in most animals.
b. Muscle originates from mesoderm.
c. The cell is the muscle fiber, specialized for contraction.
d. Striated muscles include skeletal and cardiac muscles.
84
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
7.4.
e. Smooth muscles lack the alternating bands seen in striated muscle.
f. Myofibrils are contractile elements and the unspecialized cytoplasm is sarcoplasm.
5. Nervous Tissue (Figure 7.8)
a. Nervous tissue receives and conducts impulses.
b. Nervous tissue cell types are neurons and neuroglia that support the neurons.
Animal Body Plans
A. Animal Symmetry (Figures 7.9, 7.10)
1. Spherical symmetry occurs when any plane divides the body into mirrored halves, as in cutting a
globe in half.
2. Radial symmetry occurs when any plane passing through the longitudinal axis divides the body
into mirrored halves, as in cutting a pie; the Cnidaria and Ctenophora are the Radiata.
3. Biradial symmetry occurs in an animal that is radial, except for some paired feature that allows
only two mirrored halves.
4. In bilateral symmetry, an organism can be cut in a sagittal plane into two mirror halves; this
usually provides for a head (cephalization) in bilateral animals classified in the Bilateria.
B. Body Regions
1. Anterior indicates the head end; the opposite or tail end is posterior.
2. Dorsal is the back side, and ventral is the front or belly side.
3. Medial is on the midline of the body; lateral is to the sides.
4. Distal parts are far from the body; proximal parts are near.
5. A frontal plane divides the body into dorsal and ventral halves.
6. A sagittal plane divides an animal into right and left halves.
7. A transverse plane (or cross section) separates anterior and posterior portions.
8. In vertebrates, pectoral is the chest region or area supported by the forelegs.
9. Pelvic refers to the hip region or area supported by the hind legs.
C. Body Cavities
1. The Coelom
a. The major evolutionary innovation of Bilateria is the coelom.
b. The coelom is a fluid-filled space around the gut; it provides a tube-within-a-tube
arrangement with greater flexibility.
c. A coelom provides more space for organs and surface area for exchange.
d. Worms rely on the coelom for a hydrostatic skeleton to aid in burrowing.
2. Acoelomate Bilateria (Figure 7.11)
a. Acoelomate animals lack a body cavity surrounding the gut.
b. Internal regions are filled with mesoderm and a spongy mass of parenchyma from ectodermal
cells.
c. Sometimes, parenchymal cells are cell bodies of muscle cells.
3. Pseudocoelomate Bilateria (Figure 7.12)
a. Nematodes and some others have a cavity around the gut but it is derived from the blastocoel
of the embryo.
b. It provides a tube-within-a-tube but it is not derived from mesoderm.
c. Unlike a true coelom, the pseudocoel is derived from the embryonic blastocoel.
d. Pseudocoelomates also lake a peritoneum.
4. Eucoelomate Bilateria (Figure 7.13)
a. A true coelom is lined with mesodermal peritoneum.
b. It is formed in one of two methods but both produce a mesodermal peritoneum.
1) Schizococoelous formation involves splitting of mesodermal bands that originate from
cells in the blastopore region.
2) Enteroceolous formation comes from pouches of the archenteron or primitive gut.
D. Metamerism (Segmentation) (Figure 7.14)
1. Metamerism is serial repetition of similar body segments.
2. Each segment is a metamere or somite.
3. True metamerism is found in Annelida, Arthropoda and Chordata; other groups show a superficial
segmentation.
E. Cephalization
85
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
1.
2.
3.
Differentiation of the head, or cephalization, is mainly found in bilaterally symmetrical animals.
Concentrating the sense organs at the head, as well as the mouth, is efficient for sensing and
responding to the environment and food.
Polarity is the gradient in activities between anterior and posterior ends.
Lecture Enrichment
1.
2.
3.
4.
5.
6.
7.
Why are insects so successful on land, and why there are so many different species of insects? Why are there so
many more entomologists than there are malacologists?
We do not have huge spiders or giant ants that carry away people. Query why? The essay by J.B.S. Haldane on
“Being the Right Size” can be used to provide background examples for an instructor to use.
Compare the body structure of the flatworm, the roundworm and a vertebrate with emphasis on body layers,
symmetry and coelomic development; this provides some concrete examples of the concepts.
Assigning students to construct a geometrical “humbug” based on instructions using the terms “basal” and
“distal” and “lateral” etc. can reinforce the descriptive terminology.
Emphasize that all kinds of tissues are present in nearly every organ. For example the stomach is composed of
multiple tissues: the epithelium lining the stomach's interior and exterior surfaces, muscle that allows stomach
contractions to occur, nerves that supply the impulses for those contractions and connective tissues such as
blood and connections binding the various tissues together.
Contrast the presence of sensory receptors in the head of some annelids such as sandworms with their absence
in the earthworm; ask what this suggests about the environments in which these worms live.
Veteran faculty vary in the extent they wish to cover the generalizations in this chapter. Some may choose to
integrate these concepts with the in-depth coverage of organisms provided by the later chapters.
Commentary/Lesson Plan
Background: Because many of the organisms mentioned (e.g. flatworms, cnidaria, etc.) are mostly microscopic or
remote from inland temperate populations, few students will be directly familiar with any of these aside from
previous specific targeted biology labwork. Coastal students may have some experience with marine cnidaria and
flatworms. International students from tropical countries may be willing to relate the features of some of the forms
familiar to them. Due to the small size of arthropods, most students have some experience with them, particularly
insects and spiders. Nevertheless, the astounding diversity of animal groups will require substantial visuals.
Misconceptions: Some students may believe that the basic patterns of symmetry are a major phylogenetic feature
and early zoology charts did place echinoderms directly after Cnidaria (then known as coelenterates); however, the
symmetry provides a descriptive discussion but little phylogenetic information of detailed nature. Often discussions
of the value of various evolutionary inventions leads students to believe that they are always better
(“adaptationism”) but some primitive organisms dominate their niche because they are better fitted than any
subsequent animals. Many students are surprised to find that primitive insects, for example, had more segments and
more wing veins that modern species, and that replication of metameres and veins occurred early and subsequent
evolution involved a reduction in segments and veins.
Schedule:
HOUR 1 7.1.
7.2.
New Designs for Living
A. Levels of Organization in
Organismal Complexity
Hierarchical Organization of Animal
Complexity
A. Grades of Organization
B. Complexity and Body Size
HOUR 2 7.3.
7.4.
86
Extracellular Components of the
Metazoan Body
A. Body Fluids and Extracellular
Structural Elements
B. Architectural Extracellular
Structural Elements
C. Types of Tissues
Animal Body Plans
A. Animal Symmetry
B. Body Regions
C. Body Cavities
D. Metamerism
E. Cephalization
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
ADVANCED CLASS QUESTIONS:
1. An animal’s body has levels of organization. How is each level of organization more than the sum of its parts?
2. All organisms carry out certain life processes. How do the various organ systems of animals in general
contribute features that are similar or different from plants?
3. Animals are a major group of organisms alive today. What features might you expect animals to have in
common because they are heterotrophic by ingesting food? How might this common trait cause them to be
differently adapted?
4. Why are giant ants and spiders the size of humans or elephants not possible?
Twelfth Edition Changes:
1.
2.
3.
All changes in this chapter are minor:
The appearance of metamerism in body plans was a highly significant evolutionary event.
Metamerism permits greater body mobility and complexity of structure and function.
Metamerism is found in phyla Annelida and Chordata in addition to Arthropoda, although superficial
segmentation of ectoderm and body wall may appear among diverse groups of animals.
Source Materials
[Bold = recommended; for vendor abbreviations, see list of distributors in Appendix 1]
Anatomy of the Earthworm (FH), 15-min. video
Anatomy of the Freshwater Mussel (FH), 13-min. video
Animal Defenses (JLM), slides (20)
The Animal Kingdom I and II (JLM), slide set (20)
Animal Life Series (PLP), 6 12-min. videos
Animal Structures (IM), 30-min. video
Animals of the World (Q), MS-DOS CD
The Biology of Cnidarians (NEB), 20-min. video
The Biology of Cnidarians (WARDS), 30-min. video
The Biology of Flatworms (NEB), 12-min. video
The Biology of Nematodes, Rotifers, Bryozoans and Some Minor Phyla (NEB) (WARDS), 20-min. video
Blood (FH), 23-min. video
Blood: The Microscopic Miracle (EBE), 22-min. video
Blueprint for Survival (IM), 20-min. video
The Body Atlas (AVP) (JLM), 13 25-min. videos
Body and Mind (Q), MS-DOS CD
The Body Electric (CBSC), Apple
Body Language (CBSC), Mac, MS-DOS
Body Language: Study of Human Anatomy 7-Part Series (PLP), Apple, MS-DOS
Bones and Muscles (IFB), 15-min. video
Comparative Histology (BDI), Mac and MS-DOS CD or Laserdisc
The Earthworm (CSG) (NEB), Apple, Mac, DOS
The Earthworm (NEB), Mac, Win CD
Earthworm (NEB), 10-min. video [dissection]
External Anatomy of Spiders (JLM), slide set (20)
Cnidarians (Cyber), Mac, MS-DOS CD
Cycles of Life: Exploring Biology–Animal Structure (A-CPB), 30-min. video
Flatworms (Platyhelminthes) (EBE), 16-min. video
General Zoology (BDI), Mac and MS-DOS CD or laserdisc
How We Classify Animals (Q), Mac or MS-DOS CD
Integument, The (IM), 29-min. video
Introduction to the Body: Landscapes and Interiors (FH), 26-min. video
Introduction to General Biology: The Animal Kingdom I—Introduction (Q), Mac, DOS
Introduction to General Biology: The Animal Kingdom II—Invertebrates (Q), Mac, DOS
Introduction to General Biology: The Animal Kingdom III—Vertebrates (Q), Mac, DOS
Introduction to Human Tissues (JLM), slide set (20)
Introduction to Invertebrates (FH) (IM), 30-min. video
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Invertebrates (four-part series) (IM), 30-min. video
Invertebrates (PHO), 13-min. video
The Invertebrates, Parts 1-4 (IM) 4 23-30-min. videos
Invertebrates, The: This Was the Beginning (IFB), 13-min. video
Landscapes and Interiors (FH), 27-min. video
Learning All About Animals (Q), Mac or MS-DOS CD
Life on Earth Series (PC) (CBSC), 2 2-hour videos
Looking Into the Body (PHO), 33-min. video
Mollusks (Cyber), Mac, MS-DOS CD
Mollusks: Snails, Mussels, Octopuses, and Their Relatives (EBE), 14-min. video
The Muscle Tutorial (INT), Mac
Multimedia Animals Encyclopedia (Q), Mac or MS-DOS CD
NOVA: The Little Creatures Who Run The World (CBSC) (JLM) (MBI) (NEB) (WGBH), 57-min. video
NOVA: The Universe Within (JLM) (NEB), 60-min. video
Ourselves and Other Animals (FH), 12 27-min. videos
Powers of Ten (PYR), 10-min. video [levels of organization]
Review of Biology: Design for Living (FH), 26-min. video
Sponges and Coelenterates: Porous and Saclike Animals (PHO), 10-min. video
Strange and Unusual Animals: Adaptation to Environment (AIMS), 10-min. video, laserdisc
Survey of the Animal Kingdom: The Invertebrates (ei), video
The Systematic Body (INT), Mac
Systems of the Body: An Introduction (ei), video
Tissues (IM), 29-min. video
Understanding Human Physiology 4-Part Series (PLP), MS-DOS
The Vertebrates (Cyber), Mac, MS-DOS CD
Virtual Anatomy's 3D Skeletal (SciT) Win, Mac
WARD's Basic Animal Smart Slides (WARDS), Mac, Win CD
WARD's Epithelial Cells Smart Slides (WARDS), Mac, Win CD
WARD's Exploring Animal Life (WARDS), Mac, Win CD
WARD's Histology Collection (WARDS), Mac, Win CD
The World of Animals (Q), MS-DOS CD
Worms: Flat, Round, and Segmented (PHO), 15min.video
Worms: The Annelids (EBE), 13-min. video
The World of Animals (Q), MS-DOS CD
Worms and How They Live (AIMS), Mac, Win CD, 18-min. video, laserdisc
Zoology (Invertebrates, Vertebrates) (PLP), Apple or MS-DOS
Zoology I and II (PLP), MS-DOS
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
CHAPTER
8
CLASSIFICATION AND PHYLOGENY OF ANIMALS
CHAPTER OUTLINE
8.1.
8.2.
Order in Diversity
A. History
1. All cultures classify or group animals by patterns of similarity.
2. Systematic zoologists have three goals:
a. to discover all species of animals,
b. to reconstruct their evolutionary relationships, and
c. to classify animals according to their evolutionary relationships.
3. Taxonomy is the formal system for naming and classifying species.
4. Systematics is the broader science of classifying organisms based on similarity, biogeography, etc.
5. Adjusting taxonomy to accommodate evolution has produced several methods of classification.
B. Linnaeus and the Development of Classification
1. The Greek philosopher Aristotle first classified organisms.
2. The English naturalist John Ray produced a more comprehensive system and a concept of species.
3. Carolus Linnaeus invented the current system of classification.
a. Linnaeus was a Swedish botanist with extensive experience classifying flowers.
b. He used morphology to develop a classification of animals and plants in his Systema Naturae.
4. A hierarchy of taxa is one major concept Linnaeus introduced. (Table 8.1)
a. His hierarchy contains seven major ranks: kingdom, phylum, class, order, family, genus and
species.
b. All animals are classified in kingdom Animalia, each species has its own name; the names of
animal groups at each rank in the hierarchy are called taxa (singular: taxon).
c. Each rank can be subdivided into additional levels of taxa, as in superclass and suborder, etc.
d. For large and complex groups, such as fishes and insects, up to 30 levels may be used.
5. Linnaeus introduced binomial nomenclature.
a. A scientific name of an animal consists of two words (binomial) as in Turdus migratorius.
b. The first word is the genus and is capitalized; the second is the specific epithet and is in lower
case.
c. To separate a scientific name from common text, it is always in italics or underlined if
handwritten.
d. The specific epithet is never used; the genus must be used to form the scientific name.
e. A specific epithet may be used in many names; names of animal genera must always be
different.
f. Ranks above species are single names written with a capital initial letter (e.g., Reptilia and
Cnidaria).
g. Geographic subspecies are trinomials; all three terms are in italics, and the subspecies is in
lower case. (Figures 8.1, 8.2)
h. A polytypic species contains one subspecies whose subspecific name is a repetition of the
species epithet and one or more additional subspecies whose names differ.
Taxonomic Characters and Phylogenetic Recognition
A. Homology
1. A phylogeny or evolutionary trees is based on the study of characters that vary among species.
2. Character similarity that results from common ancestry is called homology.
3. Different lineages may develop similar features independently; this is convergent evolution.
4. Characters that are similar but misrepresent common descent are nonhomologous or homoplastic.
B. Using Character Variation to Reconstruct Phylogeny (Figures 8.3, 8.4)
1. Reconstructing phylogeny requires determining ancestors and descendants.
2. The form that was present in the common ancestor is ancestral.
3. Characters that arose later are derived character states.
4. An outgroup shows if a character occurred both within and outside the common ancestor.
5. A series of species that share derived characters form a subset called a clade.
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6.
7.
8.
8.3.
The derived character shared by members of a clade is called a synapomorphy of that clade.
By identifying the nested hierarchy of clades or branches, we can form patterns of common descent.
Character states ancestral for a taxon are plesiomorphic for that taxon; sharing of ancestral states is
termed symplesiomorphy.
9. Identifying the level at which a character state is a synapomorphy may identify a clade.
10. A cladogram is a nested hierarchy of clades.
11. To obtain a phylogenetic tree, we must add important information on ancestors, duration of lineages,
and amount of change.
C. Sources of Phylogenetic Information (Figure 8.5)
1. Comparative morphology examines shapes, sizes and development of organisms.
a. Skull bones, limb bones, scales, hairs and feathers are important morphological characteristics.
b. Both living specimens and fossils are used as phylogenetic information.
2. Comparative biochemistry analyzes sequences of amino acids in proteins and nucleotides in nucleic
acids.
a. Direct sequencing of DNA and indirect comparisons of proteins sequences are comparative
methods.
b. Some recent studies use biochemical techniques to analyze fossils.
3. Comparative cytology examines variation in number, shape and size of chromosomes in living
organisms.
4. Fossils can provide information on the relative time of evolution; radioactive dating can confirm age.
5. Some protein and DNA sequences undergo linear rates of divergence; this allows us to calculate the
time of the most recent common ancestors.
Theories of Taxonomy
A. Phyletic Relationships (Figure 8.6)
1. A relationship between a taxonomic group and a phylogenetic tree or cladogram can be one of three
forms.
a. A monophyletic taxon includes the most recent common ancestor and all descendants of that
ancestor.
b. A taxon is paraphyletic if it includes the most recent common ancestor of all members of a
group but not all descendants of that ancestor.
c. A taxon is polyphyletic if it does not include the most recent common ancestor of members of
that group; the group has at least two separate evolutionary origins.
2. Both evolutionary and cladistic taxonomy accepts monophyletic and rejects polyphyletic groups;
they differ on accepting paraphyletic groups.
B. Traditional Evolutionary Taxonomy (Figures 8.7-8.9)
1. The two main principles are common descent and amount of adaptive evolutionary change.
2. A branch on a family tree represents a distinct adaptive zone; a distinct “way of life.”
3. A taxon that represents an adaptive zone is a grade; modifications of the penguin branch to
swimming are an example.
4. Evolutionary taxa may be either monophyletic or paraphyletic; chimpanzees and gorillas share a
more recent ancestor with man than with orangutans, but are in a family separate from humans.
5. By accommodating adaptive zones, nomenclature reflecting common descent is not as clear.
6. Phenetic taxonomy was another school of classification that abandoned producing phylogenetic
trees in favor of measuring overall similarity; but it has little support today.
C. Phylogenetic Systematics/Cladistics (Figure 8.10)
1. Willi Hennig first proposed cladistics or phylogenetic systematics in 1950.
2. It emphasizes common descent and cladograms.
3. In the above example, chimpanzees, gorillas and orangutans are included in Hominidae with
humans.
4. Cladists do not assert that amphibians evolved from fish or birds from reptiles; they contend that a
monophyletic group descending from a paraphyletic group contains no useful information.
5. Likewise, extinct ancestral groups are always paraphyletic since they exclude a descendant that
shares their most recent common ancestor.
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6.
8.4.
Some cladists indicate that primitive and advanced are relic ideas derived from a pre-Darwinian
“scale of nature” leading to humans near the top; groups were defined based on “higher” features
they lacked.
7. Cladists avoid paraphyletic groups by defining a long list of sister groups to each more inclusive
taxon.
D. Current State of Animal Taxonomy
1. Modern animal taxonomy was established using evolutionary systematics and recent cladistic
revisions.
2. Total use of cladistic principles would require abandonment of Linnaean ranks.
3. Sister groups relationships are clear descriptions that will replace “mammals evolved from reptiles”
paraphyletic statements that are problematic.
4. The terms “primitive,” “advanced,” “specialized” and “generalized” are used for specific
characteristics and not for groups as a whole.
5. Cladistics causes confusion by using “bony fishes” to also include amphibians and amniotes, reptiles
to include birds, but not some fossil forms, etc.
Species
A. Criteria for Recognition of Species
1. Huxley was among the first to ask, “What is a species?”
2. “Species” is easy to use, but the term “species” has been hard to define.
B. Typological Species Concept
1. Before Darwin, species were considered fixed and with essential and immutable features.
2. The typological species concept centered on an ideal form for the species; variations were
“imperfect.”
3. A type specimen was labeled and deposited in a museum to represent this “standard” specimen;
today the practice continues, but as a name-bearer to compare with potentially new species.
4. Variation in a population is now recognized as normal.
C. Biological Species Concept
1. Theodosius Dobzhansky and Ernst Mayr formulated this during the evolutionary synthesis.
2. A species is a reproductive community of populations (reproductively isolated from others) that
occupies a specific niche in nature.
3. The ability to successfully interbreed is central to the concept.
4. The criteria of “niche” tie in ecological properties.
5. However, controlled breeding experiments can be difficult to conduct.
6. Molecular and other studies may detect sibling species that are different species with similar
morphology.
7. The biological species concept lacks an explicit temporal dimension and gives little guidance
regarding the species status of ancestral populations relative to their evolutionary descendants.
8. Proponents of the biological species concept often disagree on the degree of reproductive isolation
necessary for the determination of distinct species.
D. Alternatives to the Biological Species Concept
1. Criticism
a. A species has limits in space and time; boundaries between species may be difficult to locate.
b. Species are both a unit of evolution and a rank in taxonomic hierarchy.
c. Interbreeding is not an operational definition in asexual organisms.
2. The Species in Space and Time
a. A species has a distribution in space, its geographic range.
b. A species has a distribution through time, its evolutionary duration.
c. Cosmopolitan distributions are worldwide; restricted distributions are endemic.
d. Seemingly identical populations that are isolated for thousands of years pose a species question.
3. Evolutionary Species Concept
a. Where do we set the species boundary in a lineage leading back to a fossil form?
b. Simpson provided the evolutionary species concept in the 1940s; it persists with modification.
c. An evolutionary species is a single lineage of ancestor-descendant populations that maintains its
identity from other such lineages and that has its own evolutionary tendencies and historical
fate.
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d. This definition accommodates both sexual and asexual forms as well as fossils.
Phylogenetic Species Concept (Figure 8.11)
a. The phylogenetic species is an irreducible (basal) grouping of organisms diagnosably distinct
from other such groupings and within which there is a parental pattern of ancestry and descent.
b. This is a monophyletic unit that recognizes the smallest groupings that undergo evolutionary
change.
c. It discerns the greatest number of species but may be impractical.
d. This system disregards details of evolutionary process.
E. Dynamism of Species Concepts (Figure 8.12)
1. Disagreement is a sign of dynamic research and argument.
2. No one concept is comprehensive or final; all need to be understood to understand future concepts.
Major Divisions of Life
1. Aristotle’s two kingdom system included plants and animals; one-celled organisms became a
problem.
2. Haeckel proposed Protista for single-celled organisms in 1866.
3. In 1969, R.H. Whittaker proposed a five-kingdom system to distinguish prokaryotes and fungi.
4. Woese, Kandler and Wheelis proposed three monophyletic domains above kingdom level—Eucarya,
Bacteria and Archaea—based on ribosomal RNA sequences.
5. Retaining Whittaker’s five kingdoms, the Eucarya are paraphyletic unless Protists are broken up into
Ciliata, Flagellata and Microsporidia, etc. (Figure 8.13)
6. More revisions are necessary to clarify taxonomic kingdoms based on monophyly.
7. “Protozoa” are neither animals nor a valid monophyletic taxon.
8. “Protista” is not a monophyletic kingdom but is most likely composed of seven or more phyla.
Major Subdivisions of the Animal Kingdom
1. Animal phyla have been informally grouped based on embryological and anatomical traits.
2. Protozoa constitute many phyla and none of them belong within the animal kingdom.
3. Metazoa is therefore synonymous with the animal kingdom proper.
4. In the classical outline, bilateral animals are divided into deuterostomes and protostomes; however
some phyla have mixed traits.
5. Molecular studies call into question the classification of Bilateria; protostome phyla groupings by
acoelomate, pseudocoelomate and eucoelomate may not be monophyletic.
4.
8.5.
8.6.
Lecture Enrichment
1.
2.
3.
4.
Describing the problems with Aristotle's land-air-sea classification provides students with an idea of the
limitations of some classification schemes logical for their time.
One effective but time-consuming method to understand traditional, phenistic and cladistic classification is to
work through one simple set of animals or plants by developing a table of traits and a similarity matrix. For
instance, ask for six common animals, form a chart of features they share then build a phylogeny on number of
shared traits.
Ask students why drug research proceeds first to rats, then to monkeys, and then moves to human trials. Ask for
applications of the predictive power of a phylogeny that more closely matches evolutionary history.
Several decades ago, some scientists predicted numerical taxonomy would make classification a technician’s job.
A decade ago, molecular systematists proclaimed they would provide the ultimate key to objective classification.
Students who fully comprehend the work of systematics will understand this is a field that integrates all of
biology.
Commentary/Lesson Plan
Background: Most students will have used high school textbooks that addressed classification in a classical manner
and assume it is a matter of memorizing the hierarchy of names. Most secondary biology teachers lack coursework in
systematics and therefore student misconceptions are likely.
Misconceptions: Many students have been confused by biology teachers holding up a specimen and asking students to
"name" (only one scientist gets to "name" a species), "classify," (group a species with its closest relatives) or "identify"
it, this final word being the correct usage. Identifying an organism by name is not classifying it; “classifying” is
grouping and it takes three organisms to classify so that two are more closely related than they are to a third. In
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common life, these terms are used interchangeably, but biology majors must be more careful in their use of these
terms, the process starts now. Students may assume that the number of species to be named is finite, as are the
contents of an auto parts store or a grocery store; the continual evolutionary change dimension will not be evident.
Both cladograms and phylogenies will be assumed to lead to “higher” forms on the right hand side. In practice, each
branching of a phylogeny or node of a cladogram can rotate like an inverted mobile and more recent derived forms can
be placed to the left or right at each branch.
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Schedule: If you intend to work through the concepts of “synapomorphy,” “clade,” “monophyly,” etc. and provide
detailed examples of the schools of systematics, add another hour.
HOUR 1 8.1.
8.2.
8.3.
Order in Diversity
HOUR 2 8.4.
A. History
B. Linnaeus and the Development of
Classification
Taxonomic Characters and Phylogenetic
Recognition
A. Homology
B. Using Character Variation to
8.5.
Reconstruct Phylogeny
8.6.
C. Sources of Phylogenetic Information
Theories of Taxonomy
A. Phyletic Relationships
B. Traditional Evolutionary Taxonomy
C. Phylogenetic Systematics/Cladistics
D. Current State of Animal Taxonomy
Species
A. Criteria for Recognition of Species
B. Typological Species Concept
C. Biological Species Concept
D. Alternatives to the Biological Species
Concept
E. Dynamism of Species Concepts
Major Divisions of Life
Major Subdivisions of the Animal
Kingdom
ADVANCED CLASS QUESTIONS:
1. Why can't scientists arrive at one stable classification system where the taxa names no longer change?
2. In some states, you must have a fishing license to hunt frogs. Many stores post a sign that reads "No animals
allowed," but you are technically an animal. Such regulations are often written into state laws. Why can't science
use common names rather than scientific names?
3. If organisms exist and live and die as individual organisms, why are species defined at the population level?
4. Why do cladists believe that traditional systematists are being subjective?
5. A phenistics movement called “numerical taxonomy” concluded that technicians taking measurements and
computers calculating similarities could do all classification. Australia and the United States both have dog-like,
cat-like, and rabbit-like animals but the Australia versions of these mammals have pouches (they are marsupials)
while the U.S. counterparts are placental. Why is the concept of homology important here?
Twelfth Edition Changes: Changes to this chapter were relatively minor:
1. The introductory material was edited to include an example of geographic variants (Ensatina eschscholtzii); and a
description of polytypic species.
2. A full discussion of the biological species concept and the problems inherent in the concept are discussed.
3. A better discussion of identifying which characters should be classified as ancestral and which ones as derived.
4. The Entoprocta and Gnathostomulida are added to the Lophootrochozoa and the Loricifera and Pentastomida are
added to the Ecdysozoa.
5. There are new references concerning Linnean hierarchy, phylogenetic methods, and character selection.
Source Materials
[Bold = recommended; for vendor abbreviations, see list of distributors in Appendix 1]
Biological Classification and the Five Kingdoms of Life (SK&BL), Mac, Win, CD
Classification (IM), 29-min. video
Classification of Animals (SK&BL) (VWR), 3 20-min. videos
Evolution: The 3 ½ Billion Year Journey (CAM) (Cyber) (Q), Mac, Win, MS-DOS CD
Evolve: Time & Taxonomy (PLP), Apple, MS-DOS
Five Kingdoms: Life on Earth (Q), Mac, Win CD
The Five Kingdoms of Life (PLP), 6 15-min. videos
The Five Kingdoms of Life (CBSC) (SK&BL) (VWR), Mac, Win, MS-DOS CD
The Five Kingdoms of Life 6-Part Series (CBSC), Mac
Five Kingdoms of Life Series (CBSC), slides
Organisms Classification Key (PLP), MS-DOS
Speciation (ei), slides
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Copyright © 2005 – The McGraw-Hill Companies srl
Structural Homologies and Co-evolution (FH), 20-min. video
Three Billion Years of Life: The Drama of Evolution (GA), 70-min. video
Taxonomy: How Living Organisms Differ (IM), 36-min. video
95
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PART
IV
ACTIVITY OF LIFE
29 Support, Protection, and Movement ............................. 271
30 Homeostasis.................................................................. 281
31 Internal Fluids and Respiration..................................... 290
32 Digestion and Nutrition ................................................ 300
33 Nervous Coordination................................................... 307
34 Chemical Coordination................................................. 319
35 Immunity ...................................................................... 328
36 Animal Behavior........................................................... 335
____________________________________________________________________________________________
CHAPTER
9
SUPPORT, PROTECTION, AND MOVEMENT
CHAPTER OUTLINE
9.1.
Integument Among Various Grups of Animals
A. General
1. The integument is the outer covering that includes skin, hair, setae, scales, feathers and horns.
2. It is usually tough and pliable, providing mechanical protection against abrasion.
3. It provides moisture proofing for sealing water in or out.
4. It is a vital barrier against invasion by bacteria.
5. Skin also protects underlying cells against damage by ultraviolet sunlight.
6. In endothermic animals, it is concerned with temperature regulation including insulation and cooling.
7. Skin contains sensory receptors.
8. It has excretory functions and sometimes respiratory functions as well.
9. Skin pigmentation may assist in camouflage and signaling.
10. Skin secretions may make the animal sexually attractive or influence other animals’ behaviors.
B. Invertebrate Integument (Figure 9.1)
1. Protozoa have plasma membranes or a protective pellicle.
2. Most multicellular invertebrates have complex tissue coverings.
3. Some secrete a noncellular cuticle over the epidermis.
4. A molluscan epidermis is soft and contains mucous glands; some secrete the calcium carbonate shell.
5. Cephalopods have a more complex integument of cuticle, simple epidermis, connective tissue,
reflecting cells, and a thicker layer of connective tissue.
6. Arthropod Exoskeleton
a. The firmness of the exoskeleton, and jointed appendages, allows for muscle attachment.
b. A single-layered epidermis or hypodermis secretes a cuticle with two zones.
c. The thicker, inner procuticle is made of protein and chitin layers.
d. The thin epicuticle is nonchitinous, made of proteins and lipids, and provides moisture-proofing.
e. Arthropod cuticle may remain soft and flexible as in small crustaceans and insect larvae.
f. Decapod cuticle is hardened by deposition of calcium carbonate in the procuticle (calcification).
g. Insect cuticle hardens by sclerotization, formation of cross-linkages between procuticle lamellae.
h. Arthropod cuticle is one of the toughest animal materials, yet it is very light.
7. Molting
a. The epidermal cells divide by mitosis.
b. Enzymes secreted by the epidermis digest most of the procuticle; digested materials are absorbed.
c. In the space beneath the old cuticle, a new epicuticle and procuticle are formed.
d. After the old cuticle is shed, the new cuticle is thickened and calcified or sclerotized.
C. Vertebrate Integument and Derivatives (Figures 9.1B-C, 9.2, 9.3)
1. Structure
a. An example of vertebrate skin is frog or human skin.
b. The thin, outer stratified epithelial layer is epidermis derived from ectoderm.
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c.
d.
9.2.
The inner, thicker layer is dermis derived from mesoderm.
The dermis contains blood vessels, collagenous fibers, nerves, pigment cells, fat cells and
connective tissue cells, all to support and nourish the epidermis.
e. The epidermis is stratified squamous epithelium.
f. The basal part is made of cells that undergo frequent mitosis to renew the layers above it.
g. As outer cells are displaced upward, fibrous protein keratin accumulates inside the cells.
h. Cells die as the keratin accumulates to replace the metabolically active cytoplasm.
i. Cornified, or dead transformed cells, are shed as household dust and dandruff.
j. While still on the body, the cornified cells are resistant to abrasion and are the stratum corneum.
k. This area thickens when exposed to constant pressure, such as calluses and footpads of mammals.
l. Dermis supports the epidermis; any bony structures derive from dermis tissue.
m. Scales of contemporary fishes are bony dermal structures evolved from bony armor of early
fishes.
n. Most amphibians lack dermal bones in their skin.
o. In reptiles, dermal bones form the armor of crocodilians, the beaded skin of lizards, and
contribute to the shell of turtles.
p. Claws, beaks, nails and horns are made up of combinations of epidermal and dermal components.
2. Animal Coloration (Figure 9.4, 9.5)
a. Structural colors are produced by the physical structure of the surface tissues.
b. More common are pigments, varied molecules that reflect specific light rays.
c. In crustaceans and ectothermic vertebrates, these pigments are in large cells with branching
processes called chromatophores.
d. Pigments may concentrate in the center of a cell or disperse throughout the cell for display.
e. Cephalopod chromatophores are different; each small sac-like cell with pigment is surrounded by
muscle cells that can stretch the cell into a pigmented sheet—a rapid response system.
f. Melanins are black or brown polymers responsible for earth-colored shades.
g. Carotenoid pigments provide yellow and red colors often contained inside xanthophores.
h. Ommochromes and pteridines are responsible for yellow pigments of molluscs and arthropods.
i. Green is usually produced by yellow pigment overlying blue structural color.
j. Iridophores contain crystals of guanine or another purine rather than pigment; they produce
silvery or metallic colors.
k. Mammals are relatively uncolorful, a fact related to their being mostly colorblind.
l. Primates are an exception, and the brilliant skin patches of baboons and mandrills reflect this.
m. Dermal melanophores deposit melanin in growing hair of mammals, providing the muted color.
3. Injurious Effects of Sunlight
a. Human sunburn is one demonstration of the damaging effect of ultraviolet radiation on cells.
b. Protozoans or flatworms exposed to sun in shallow water are damaged or killed.
c. Arthropod cuticle and scales, feathers and fur of the various vertebrates provide protection.
d. Sunburn is caused by dermal and epidermal cells releasing histamines causing vessels to enlarge.
e. A suntan is due to melanin pigment built up in deeper epidermis, and pigment darkening.
f. Sunlight causes about one million new cases of skin cancer annually in the United States.
g. High doses of sunlight in childhood cause genetic mutations that cause skin cancer when older.
Skeletal Systems
A. Hydrostatic Skeletons (Figure 9.6)
1. Many invertebrates use their body fluids as an internal hydrostatic skeleton.
2. Muscles in the body wall of an earthworm contract against the coelomic fluids that are
incompressible.
3. In a body divided into compartments by septa, each surviving part can still develop pressure and
move.
4. The elephant trunk, tongues of mammals and reptiles, and tentacles of cephalopods are examples of
muscular hydrostats based on muscles arranged in cross-wise patterns.
B. Rigid Skeletons
1. Rigid skeletons provide rigid elements to which muscles can attach.
2. Muscles can only contract; to be lengthened, they must be extended by pull of an antagonistic muscle.
3. Antagonistic muscles are functional opposites that oppose the other’s action.
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4.
The exoskeleton is a protective skeleton that often must be molted to allow growth; in the case of
molluscs, the shell grows with the animal.
5. The endoskeleton is found in echinoderms and vertebrates.
6. The vertebrate endoskeleton is composed of bone and cartilage; it protects and supports, is the major
reservoir for calcium and phosphorus, and is the origin of blood cells.
C. Notochord and Cartilage
1. The notochord is a semirigid supportive axial rod of the protochordates and all vertebrate larvae.
2. Except in jawless vertebrates, a notochord is surrounded or replaced by backbone during
development.
3. Cartilage is a major skeletal element of jawless fishes and elasmobranchs; the cartilage is a derived
feature since their Paleozoic ancestors had bony skeletons.
4. Hyaline cartilage is the basic form of cartilage made of cartilage cells surrounded by firm complex
protein gel interlaced with a meshwork of collagenous fibers.
5. Blood vessels are missing in cartilage; this is the reason many sport injuries heal poorly.
6. Hyaline cartilage also makes up articulating surfaces of bone joints of adult vertebrates, as well as
supporting tracheal, laryngeal and bronchial rings.
7. In some invertebrates, cartilage occurs in the radula of gastropods and lophophore of brachiopods.
8. Cephalopods have cartilage with long, branching processes that resemble cells of vertebrate bone.
D. Bone (Figure 9.7)
1. Bone Types
a. Bone is living tissue with significant deposits of calcium salts in an extracellular matrix.
b. Bone is nearly as strong as cast iron, yet only one-third as heavy.
c. Bone is always laid down in a “replacement area” formed by some connective tissue.
d. Most bone develops from cartilage and is called endochondral or replacement bone.
e. Embryonic cartilage is eroded, leaving honeycomb spaces that are invaded by bone-forming
cells.
f. Bone-forming cells deposit calcium salts around the strandlike remnants of the cartilage.
g. Intramembranous bone develops from sheets of embryonic cells, mainly the face and cranium.
h. Cancellous, or spongy, bone has an open, interlacing framework of bony tissue.
i. Some bones proceed to add additional salts to become compact bone.
2. Microscopic Structure of Bone
a. Compact bone has a calcified bone matrix arranged in concentric rings.
b. The rings contain cavities (lacunae) filled with bone cells (osteocytes).
c. Lacunae are interconnected with canaliculi passages that distribute nutrients.
d. The whole cylindrical structure is an osteon or haversian system.
e. Osteoclasts slowly resorb bone while osteoblasts deposit additional bone.
f. These simultaneous processes allow the growth of a rigid structure without any weakening.
g. Parathyroid hormone stimulates bone resorption; calcitonin inhibits bone resorption.
h. Both hormones, together with a derivative of vitamin D, maintain constant blood calcium levels.
i. Bone growth also responds to usage; astronauts living without gravity suffer bone loss.
3. Plan of the Vertebrate Skeleton (Figures 9.8, 28.9)
a. The vertebrate skeleton is composed of the axial and appendicular skeleton.
1) The axial skeleton includes skull, vertebral column, sternum and ribs.
2) The appendicular skeleton includes limbs and pectoral and pelvic girdles.
b. Skull
1) Movement from water to land forced dramatic changes in body form.
2) Increased cephalization made the skull the most intricate part of the skeleton.
3) Some early fishes had 180 skull bones.
4) Over time, many skull bones were lost or fused.
5) Amphibians have from 50 to 95, mammals have 35 or fewer and humans have 9.
c. Vertebral Column
1) The vertebral column is the main stiffening axis and serves the same function as a notochord.
2) Movement from water to land resulted in selection for withstanding new vertebral stresses
from the two pair of appendages.
3) Vertebrae are separated into cervical thoracic, lumbar, sacral and caudal.
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9.3.
4) In birds and humans, the caudal vertebrae are reduced in size and number and sacral
vertebrae are fused.
5) The python has over 400 vertebrae.
6) A young child has 33 vertebrae; in adults, five fuse to form the sacrum and four form the
coccyx.
7) Humans have 7 cervical or neck vertebrae, 12 thoracic, and five lumbar or back vertebrae.
8) The number of cervical vertebrae is seven; this is constant in nearly all mammals.
9) The first cervical vertebra is the atlas; it supports the skull and allows it to pivot.
10) The second cervical vertebra is the axis; it allows the head to turn side-to-side.
d. Ribs
1) Fishes have a pair of ribs for every vertebra.
2) They serve as stiffening rods and improve effectiveness of muscle contractions.
3) Some vertebrates have reduced ribs; the leopard frog has no ribs at all.
4) In mammals, the ribs from the thoracic basket prevent collapse of the lungs.
5) Sloths have 24 pairs of ribs; horses possess 18 pairs.
6) Primates other than humans have 13 pairs of ribs; humans have 12 pairs, rarely a 13th pair.
e. Appendages
1) Most vertebrates have paired appendages.
2) Fishes, except agnathans, have pectoral and pelvic girdles supporting pectoral and pelvic
fins.
3) Tetrapods, unless they are limbless, have two pairs of pentadactyl limbs.
4) Even when highly modified, living and fossil tetrapods have the same homologous limb.
5) Horses have gained speed by evolution of a longer third toe.
6) Bird embryos demonstrate 13 distinct wrist and hand bones that reduce to three in adults.
7) In tetrapods, the pelvic girdle is firmly attached to transmit force.
8) The pectoral girdle is more loosely attached to allow greater freedom for manipulation.
6. Effect of Body Size on Bone Stress (Figure 9.10)
a. Cross-section-to-volume-ratio
1) Consider one animal twice as long, wide and tall as a second animal.
2) The larger animal would have eight times the volume and eight times the weight.
3) However, the cross-sectional area of bones, tendons and muscles would be four times
greater.
4) Therefore, eight times the weight would have to be carried by four times the strength.
5) Mammalian bone is uniform per cross-sectional area and this places an upper limit on size.
6) Bone shape does not change much; mammals adapted by shifting posture and alignment.
7) Mechanical advantage can be gained by aligning weight with ground reaction forces, as is
the case with an upright horse; beyond the size of a horse, not much advantage can be
gained.
8) Elephants and large dinosaurs had thick and robust bones but this decreases running speed.
Animal Movement
A. Mechanism
1. Animal movement is an important characteristic of animals, compared to plants.
2. Movements include streaming of cytoplasm and massive muscle movements.
3. Most animal movement relies on a single fundamental mechanism: contractile proteins.
4. Contractile machinery is composed of ultrafine fibrils: fine filaments, striated fibrils or tubular fibrils.
5. All are arranged to contract when powered by ATP.
6. The most important protein contractile system is composed of actin and myosin.
7. The acto-myosin system is almost universal and is found from protozoa to vertebrates.
8. However, cilia and flagella are composed of different proteins.
B. Ameboid Movement
1. Ameboid movement is found not only in amebas, but also in wandering cells of metazoans.
2. Ameboid cells change shape by extending and withdrawing pseudopodia on any cell surface.
3. Under the plasmalemma is a non-granular gel-like ectoplasm that encloses a more liquid endoplasm.
4. Under one model, as the pseudopod extends, hydrostatic pressure forces actin subunits into the
pseudopod where they assemble into a network to form a gel.
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Copyright © 2005 – The McGraw-Hill Companies srl
5.
6.
At the trailing edge of the gel, the network disassembles and freed actin interacts with myosin to
create a contractile force that pulls the cell along.
Locomotion is assisted by membrane-adhesion proteins that attach to the substrate to provide traction.
C. Ciliary and Flagellar Movement (Figures 9.11, 9.12)
1. Cilia are minute, hairlike, motile processes that extend from the surfaces of many animal cells.
2. It is a distinctive feature of ciliate protozoans.
3. Except for nematodes, where they are absent, they are found in all major animal groups.
4. Cilia function to move whole unicellular organisms and ctenophores.
5. Cilia also propel fluids and materials across epithelial surfaces in larger animals.
6. Everywhere cilia are found, they have a uniform diameter of 0.2 to 0.5 micrometers.
7. Each cilium contains a peripheral circle of nine double microtubules around two central microtubules.
8. Exceptions to this “9+2" arrangement are the “9+1" and “9+0" sperm tails of flatworms and mayflies.
9. Each microtubule has a spiral array of protein subunits called tubulin.
10. The microtubule doublets around the periphery are connected to each other and the central pair.
11. Extending from each doublet is a pair of arms composed of the protein dynein.
12. Dynein arms act as cross bridges between doublets and produce a sliding force between microtubules.
13. The flagellum is whiplike, longer than a cilium and present in fewer numbers.
14. Flagella are found in flagellate protozoans, animal spermatozoa, and in sponges.
15. Flagella differ more in their beating pattern than in structure.
16. A flagellum beats symmetrically with snakelike undulations to propel water parallel to the long axis.
17. A cilium beats asymmetrically with a fast power stroke in one direction followed by a slow recovery;
water is propelled parallel to the ciliated surface.
18. Although the mechanism of ciliary movement is not fully understood, the microtubules behave
similar to the sliding microtubule hypothesis described for muscle cell movement.
D. Muscular Movement
1. Contractile Tissue
a. Contractile tissue is most highly developed in muscle cells, called fibers.
b. During ciliary flexion, dynein arms link to adjacent microtubules, swivel and release in cycles.
2. Types of Vertebrate Muscle (Figures 9.13-9.15)
a. Striated Muscle
1) Striated muscle is transversely striped with alternating dark and light bands.
2) Striated or skeletal muscle is organized into sturdy, compact bundles.
3) Skeletal muscles attach to skeletal elements and move the trunk, appendages, eyes, etc.
4) Skeletal muscle fibers are very long, cylindrical cells with many nuclei.
5) They are packed together in bundles called fascicles and are enclosed in connective tissue.
6) Fascicles are grouped into a discrete muscle enclosed in thin connective tissue.
7) Some muscles taper at ends as they connect by tendons to bone; others are flattened sheets.
8) Skeletal muscle contracts powerfully and quickly, but fatigues more rapidly than smooth
muscle.
9) Skeletal muscle, called voluntary muscle, is stimulated by motor fibers under conscious
control.
b. Smooth Muscle
1) Smooth or visceral muscle lacks the alternating bands or striations.
2) Cells are long, tapering strands, each containing a single nucleus.
3) Smooth muscle cells form sheets of muscle circling the walls of the alimentary canal, blood
vessels, respiratory passages, and urinary and genital ducts.
4) Smooth muscle is slow acting; it maintains prolonged contractions using little energy.
5) Controlled by the autonomic nervous system, contractions are involuntary and unconscious.
6) Most smooth muscles push material in a tube or regulate tube diameter.
c. Cardiac Muscle
1) Cardiac muscle has striations but is uninucleate with branching cells.
2) It is the muscle tissue of the vertebrate heart and is seemingly tireless.
3) It is fast acting and striated like skeletal muscle, but contraction is under autonomic control.
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
3.
4.
5.
6.
4) The heartbeat originates within the specialized muscle; the autonomic nerves merely speed
up or slow down this rate.
5) Cardiac muscle is composed of closely opposed but separate uninucleate cell fibers.
Types of Invertebrate Muscle
a. Giant barnacles and Alaska king crabs have giant muscle fibers 3 mm in diameter and 6 cm long.
b. Such large cells are important in studying muscle physiology.
c. There is a wide variety of invertebrate muscles; two are described here.
d. Bivalve Molluscan Adductor Muscles
1) Scallops use “fast” striated muscle fibers to close its valves during its swimming actions.
2) A slower smooth muscle is able to keep up long-lasting contraction for hours or days.
3) Slow adductors use very little energy and require very little stimulation to keep contracted.
4) The contracted state resembles a “catch mechanism” with stable cross-linkages.
e. Insect Flight Muscles
1) Some small flies can beat their wings faster than 1000 beats per second.
2) This fibrillar muscle contracts at frequencies much faster than any vertebrate muscle.
3) A wing leverage system is arranged so the muscles shorten very little during each downbeat.
4) Muscles and wings operate as a rapidly oscillating system in an elastic thorax.
5) Rebounding elastically and activated by stretch, they do not need one impulse per
contraction.
6) One reinforcement impulse for every 20-30 contractions is enough to keep the system active.
Structure of Striated Muscle
a. Striated muscle is named for the periodic bands visible under the light microscope.
b. Each cell or fiber is a multinucleated tube with many myofibrils packed together.
c. The cell membrane folds in to form the sarcolemma.
d. A myofibril contains thick filaments of protein myosin and thin filaments of protein actin.
e. Thin filaments are held together by a dense structure called the Z line.
f. The sarcomere extends between successive Z lines.
g. Repeated, high-intensity, short exercises cause synthesis of additional actin and myosin.
h. Endurance exercise develops more mitochondria, myoglobin and capillaries.
i. Thick Filaments
1) Each thick filament is made of myosin molecules packed together in a bundle.
2) Each myosin molecule has two polypeptide chains, each having a club-shaped head.
3) The double heads of each myosin molecule face outward from the center of the filament.
4) The heads act as molecular cross bridges that interact with the thin filaments in contraction.
j. Thin Filaments
1) Thin filaments are composed of three different proteins.
2) The backbone is a double strand of actin twisted into a double helix.
3) Surrounding the actin filament are two strands of tropomyosin that lie in the grooves of
actin.
4) Each tropomyosin is a double helix.
5) The third protein of the thin filament is troponin, a complex of three globular proteins.
6) Troponin is a calcium-dependent switch that acts as the control point in contraction.
Sliding Filament Model of Muscle Contraction (Figure 9.16)
a. A sliding filament model was proposed independently in the 1950s by two English physiologists.
b. According to this model, the thick and thin filaments link together by molecular cross bridges.
c. They then act as levers to pull the filaments past each other.
d. The cross bridges on the thick filaments snap rapidly back-and-forth, attaching and releasing
from special receptor sites on the thin filaments.
e. This ratchet action draws the Z lines together.
f. All sarcomere units shorten together as the muscle contracts.
g. Relaxation is passive; when the cross bridges between thick and thin filaments release, the
sarcomeres are free to lengthen.
h. This requires some force, usually supplied by antagonistic muscles or by gravity.
Control of Contraction
a. Muscles contract in response to nerve stimulation.
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Copyright © 2005 – The McGraw-Hill Companies srl
When a nerve to a muscle is severed, the muscle atrophies or wastes away.
Skeletal muscles are innervated by motor neurons whose cell bodies are located in the spinal
cord.
d. Each cell body leads to an axon that branches to many terminal points on a muscle.
e. Each terminal branch innervates a single muscle fiber; a single motor axon may innervate a few
fibers (for precise control) or up to 2000 muscle fibers (for general effect).
f. The motor neuron and all of the muscle fibers it innervates are a motor unit.
g. When a motor neuron fires, the action potential passes simultaneously to all motor units.
h. The total force of the muscle contraction depends on the number of motor units activated.
i. Precise control of movement requires varying the number of motor units activated at one time.
j. Motor unit recruitment is a steady increase in muscle tension by increasing the motor units.
The Myoneural Junction (Figure 9.17)
a. A motor axon terminates on a muscle fiber at the myoneural junction.
b. At this junction is a tiny synaptic cleft.
c. The neuron stores acetylcholine in small synaptic vesicles.
d. When the nerve impulse reaches the cleft, the acetylcholine is released.
e. Acetylcholine causes depolarization of the muscle fiber membrane.
f. This depolarization spreads through the muscle fiber causing it to contract.
g. The synapse provides a chemical bridge that couples the nerve impulse and muscle fibers.
h. On the sarcolemma surface are numerous invaginations that project as tubules into a muscle
fiber.
i. This is called a T-system and it is continuous with the sarcoplasmic reticulum, fluid-filled
channels that run parallel to the myofilaments.
Excitation-Contraction Coupling (Figure 9.18)
a. In resting muscle, the tropomyosin strands block the myosin heads from attaching with actin.
b. When muscle is stimulated, the electrical depolarization causes calcium ions to be released from
the sarcoplasmic reticulum.
c. When calcium binds to troponin, the troponin changes shape, which allows the tropomyosin to
move out of its blocking position.
d. This exposes the active sites on actin myofilaments and the myosin heads begin binding to them.
e. Attach-Pull-Release Cycle
1) Release of bond energy from ATP activates the myosin head, which swings 45 degrees and
releases a molecule of ADP.
2) This power stroke pulls the actin filament about 10 nanometers.
3) This pull comes to an end when another ATP molecule binds to the myosin head,
inactivating the site.
4) Each cycle of attach-pull-release requires expenditure of energy in the form of ATP.
f. Shortening continues as long as nerve stimulation keeps free calcium available.
g. The attach-pull-release cycle can repeat 50-100 times per second.
h. While each sarcomere shortens a very small distance, the pull is magnified by the thousands of
sarcomeres lying end to end in a muscle fiber.
i. A strongly contracting muscle may shorten by one-third its resting length.
j. When stimulation stops, calcium is pumped back into the sarcoplasmic reticulum.
Energy for Contraction
a. Muscle contraction requires large amounts of energy.
b. The ATP normally present will sustain contraction only a second or two.
c. Creatine phosphate is a high-energy phosphate compound that stores bond energy while at rest.
d. Creatine phosphate releases stored bond energy to convert ADP to ATP in the reaction:
1) Creatine phosphate + ADP –> ATP + Creatine
e. Within a few to 30 seconds, the reserves of creatine phosphate are depleted.
f. Glycogen is the third and largest store of energy.
g. Glycogen is a chain of glucose molecules and is stored in the liver and in muscle.
h. Glycogen is abundant, can be mobilized quickly, and provides energy under anoxic conditions.
i. As creatine phosphate declines, enzymes convert glycogen into glucose-6-phosphate.
j. This first stage of glycolysis proceeds into mitochondrial respiration and generates ATP.
b.
c.
7.
8.
9.
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
k.
If muscle contraction is not too vigorous or prolonged, glucose is completely oxidized to carbon
dioxide by aerobic respiration.
l. During prolonged exercise, the blood cannot provide enough oxygen for complete oxidation.
m. The contractile machinery must then receive energy from anaerobic glycolysis.
n. Without anaerobic glycolysis, all heavy muscular exertion would be impossible.
o. Anaerobic glycolysis degrades glucose to lactic acid; energy released is used to resynthesize
creatine phosphate.
p. Lactic acid accumulates in the muscle and diffuses into general circulation.
q. Continued muscular exertion causes a buildup of lactic acid that leads to fatigue.
r. Muscles incur an oxygen debt because accumulated lactic acid must be oxidized by extra
oxygen.
s. Oxygen consumption must remain elevated until all lactic acid has been oxidized.
E. Muscle Performance
1. Fast and Slow Fibers
a. Skeletal muscles have several types of fibers.
b. Slow fibers are specialized for slow, sustained contractions without fatigue (e.g. posture).
c. Slow fibers constitute red muscles because they contain a rich blood supply, a high density of
mitochondria, and abundant stored myoglobin oxygen reserves.
d. Two kinds of fast fibers provide fast, powerful contractions.
e. One type of fast fiber lacks efficient blood supply and high density of mitochondria and
myoglobin; they are pale in color and, function anaerobically and fatigue rapidly.
f. White meat of chicken is an example of this fast fiber muscle.
g. Another kind of fast fiber has the extensive blood supply, mitochondria and myoglobin and
functions aerobically and can sustain exercise for long periods of time.
h. Geese, dogs and ungulates have limb muscles with a high percentage of fast aerobic fibers.
i. The cat family has running muscles made up almost entirely of fast fibers that operate
anaerobically.
j. Such muscles rapidly build up an oxygen debt; cheetahs must rest 30-40 minutes after a chase.
2. Importance of Tendons in Energy Storage (Figure 9.19)
a. During walking and running, kinetic energy is stored from step to step.
b. A kangaroo also uses the recoil of energy in tendons to bound along; therefore each movement
does not have to rely on alternate muscle contractions and relaxations.
c. Elastic storage occurs in legs of grasshoppers and fleas, wing hinges of flying insects, hinge
ligaments of bivalve molluscs, and the dorsal ligament that supports the head of hoofed
mammals.
Lecture Enrichment
1.
2.
3.
4.
A long balloon can be used to illustrate muscular hydrostats; when the “muscle cell” balloon shortens, it becomes
fatter and when other muscles that wrap around it constrict, the “muscle cell” is elongated.
The continuous restructuring of bone during growth is a process that has no analogies in the human construction
world; it is somewhat like expanding a small brick room into a large brick building without ever allowing the
structure to become weak from removing bricks or wedging new ones in! Osteoblasts and osteoclasts can
accomplish what we cannot.
This is a good place to begin the concept that the blood maintains a constant pool of nutrients (e.g. the amino acid
pool, the calcium pool, etc.) by organs and tissues storing or releasing the nutrients based on hormonal responses.
Bears that hibernate are not using their bones; yet they do not suffer bone loss and we do not yet know the reason.
Discovering this mechanism might provide a basis for astronauts having bone loss while in space.
Commentary/Lesson Plan
Background: Cartilage is rather commonly seen by anyone eating chicken breasts; the keel underneath the long spears
of white meat tapers from bone into milky and bendable cartilage.
Misconceptions: Few students realize that the surface of other people that we see is dead skin cells; to inspect living
tissues directly, you would have to look into someone’s eye with a special scope. Students often conceptualize bone as
relatively nonliving since it is “rock-hard”; in reality, bone is active tissue heavily infused with blood vessels and
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Copyright © 2005 – The McGraw-Hill Companies srl
indeed, bone surgery is very bloody, while cartilage is the inactive and bloodless tissue. High school biology texts
usually explain all muscles as antagonist pairs. Therefore in structures that lack bones, the fact that muscle cells never
forcibly extend themselves is not intuitive and appears to contradict our ability to lick stamps, etc. The textbook
explanation of muscular hydrostats will be new to many students. The reduction in the number of skull bones over
time, and the loss of bones in limbs, are again cases where evolution proceeds to lose or fuse bones and reduce the
number of structures, in contradiction to many students’ understanding of evolution as an increase in number and
complexity. From general biology discussions which relate many traits to number of cells, students may incorrectly
assume that bigger muscles are due to more cells.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Schedule:
HOUR 1 9.1.
9.2.
Integument Among Animal Groups
A. General
B. Invertebrate Integument
C. Vertebrate Integument and
Derivatives
Skeletal Systems
A. Hydrostatic Skeletons
B. Rigid Skeletons
C. Notochord and Cartilage
D. Bone
HOUR 2 9.3.
Animal Movement
A. Mechanism
B. Ameboid Movement
C. Ciliary and Flagellar Movement
D. Muscular Movement
E. Muscle Performance
ADVANCED CLASS QUESTIONS:
1. Why does a suntan soon wear off? If the melanin molecule is stable and does not break down, where does the
melanin go?
2. Many katydids and long-horned grasshoppers are a strong green color when living, but after being dried in an
insect collection, slowly “fade” to a yellow color. Why?
3. When a mother is pregnant, the embryo or fetus has priority on nutrients such as calcium. Why is tooth and bone
erosion a problem for pregnant women—detail exactly what sequences of physiological events transfer calcium
from her teeth to the infant—and how does a physician prevent this loss?
4. When a person has big biceps, do they have more muscle cells or just larger cells? Why?
5. What is the physiological cause of some muscles having fine control and other muscles having very coarse control?
6. What is the physiological difference between a small muscle acting to pick up a pencil and the same muscle acting
to lift a large weight?
Twelfth Edition Changes: Only minor changes have been made in this chapter:
1.
2.
3.
4.
5.
6.
Cells in the connective tissue layer (macrophages, mast cells, and lymphocytes) provide a first line of defense
if the outer epidermal layer is breached.
Most amphibians lack dermal bones in their skin except for vestiges of dermal scales found in a few tropical
caecilian species.
Recent analysis of Tyrannosaurus rex suggests that it could not run (it apparently would have had less than
half enough leg muscle mass to run and could only walk).
Cilia have a basal body (kinestosome) that is structurally similar to a centriole.
The actin filament complexes extend outward from both sides of the Z oline and overlap with myosin bundles
toward the center of each sarcomere.
The sarcopolasmic reticulum stores calcium and releases it around the actin and myosin filaments in response
to depolarization.
Source Materials
[Bold = recommended; vendor abbreviations are provided in Appendix 1]
Anatomy and Physiology (VDISC), laserdisc
Aquatic Locomotion (UC), 16-min. videoBiochemistry of Muscle (CBSC) (ei), Apple II, MS-DOS
Biochemistry of Muscle (CAM), Mac, Win CD
Biomedical Software: Neuromuscular Concepts (PLP), Apple
Biomedical Software: Skeletal Muscle Anatomy and Physiology (PLP), Apple
Body Atlas: Muscle and Bone (AVP) (JLM), 30-min. video
Body Atlas: Skin (AVP) (JLM), 30-min. video
Body Language: Muscular System and Skeletal System (PLP), Apple, MS-DOS or Mac
Bones and Muscles (IFB), 15-min. video
Cardiac Muscle Mechanics (Q), MS-DOS
Comprehensive Review in Biology: Support, Locomotion and Behavior (Q), Mac, Win
Cycles of Life: Exploring Biology–Animal Structure (A-CPB), 30-min. video
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Exercise Physiology (PLP), MS-DOS
Frog Gastrocnemius Muscle (INT), Mac
Graphic Human A and P Tutor: Muscular System and Skeletal System (PLP), MS-DOS
Growing Old in a New Age–How the Body Ages (A-CPB), 1-hr. video
Growing Old in a New Age–Illness and Disability (A-CPB), 1-hr. video
How the Body Works: Skin, Bones and Muscles (AIMS), Mac, Win CD, 19-min. video, laserdisc
Human Body Series: Muscular System (PHO), 12-min. video
Human Body Series: Skeletal System (PHO), 12-min. video
The Interactive Skeleton 1.1 (IM) (Q), Mac, Win CD
Introduction to General Biology: The Human Body II (Q), Mac, DOS
Locomotion of Four-footed Animals (UC), 15-min. video
Locomotion and Skeletons (IM), 29-min. video
MacExercise (INT), Mac
Mechanical Properties of Active Muscle (Q) (TS), MS-DOS
Mechanics of Flight in Flying Foxes (UC), 8-min. video
Moving Parts (FH), 26-min. video
Muscle (CRM), 26-min. video
Muscle and Bone (IM), 25-min. video
Muscle Contraction (ei), slides or video
Muscle Power (FH), 26-min. video
Muscle Tutorial (INT), Mac
Muscle: A Study of Integration (CRM), 25-min. video
Muscle: Chemistry of Contraction (EBE), 21-min. video
Muscle: Electric Activity of Contraction (EBE), 9-min. video
Muscle Mechanics: A Computer-Simulated Experiment (C-BE), MS-DOS
The Muscle Tutorial (INT), Mac
Muscles and Exercise (IM), 29-min. video
Muscles and Joints: Moving Parts (FH), 26-min. video
Muscles and Joints: Muscle Power (FH), 26-min. video
Muscular and Skeletal Systems (IM), 20-min. video
Muscular System (IM), 12-min. video
Neuromuscular Junction: Physiology (IM), 23-min. video
NEUROSIM II (STAT), MS-DOS
Osteoporosis: Progress and Prevention (FH), 24-min. video
Physiology of Exercise (FH), 15-min. video
Riddle of the Joints (PHO), 58-min. video
SimMuscle (THIEME), Mac, Win CD
Skeletal System (PHO), 12-min. video
Snake Locomotion (UC), 12-min. video
The Physiology of Exercise (FH), 15-min. video
Ultimate 3-D Skeleton (Q), Mac, Win CD
WARD's Epithelial Cells Smart Slides (WARDS), Mac, Win CD
WARD's Histology Collection (WARDS), Mac, Win CD
281
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
CHAPTER
10
HOMEOSTASIS
CHAPTER OUTLINE
10.1.
Water and Osmotic Regulation (Figures 10.1, 10.2)
A. Marine Invertebrates Meet Problems of Salt and Water Balance
1. Most marine invertebrates are in osmotic equilibrium with their seawater environment.
2. With body surfaces permeable to water and salts, the internal and external concentrations are equal.
3. Such animals that cannot regulate osmotic pressure of their body fluids are called osmotic
conformers.
4. This functions for open ocean organisms because the open ocean is stable.
5. Animals that must live within a narrow salinity range are stenohaline.
6. Organisms that can tolerate the wide variations found in estuaries are euryhaline.
7. A hyperosmotic regulator maintains body fluids in higher concentration than surrounding water.
8. Kidneys, or antennal glands in a crab, can maintain a higher concentration by excreting excess water.
9. Salt-secreting cells in the gills that remove ions from seawater counter loss of salt ions.
10. Any process that requires an expenditure of energy is an active transport process.
11. Any process that works against the diffusion gradient will require active transport.
12. Systems within an organism function in an integrated way to maintain a constant internal
environment around a setpoint.
B. Invasion of Fresh Water (Figures 10.3, 10.4)
1. During Silurian and Devonian periods, jawed fishes began to penetrate brackish and freshwater
rivers.
2. The unexploited habitat with abundant food presented a physiological evolutionary challenge.
3. Freshwater fishes must prevent salt loss and unload excess water.
4. The scaled and mucus-covered surface of a fish is nearly waterproof.
5. Water that enters by osmosis across the gills is pumped out by the kidney as very dilute urine.
6. Salt-absorbing cells in the gills move sodium and chloride ions from water to blood.
7. Salt present in the fish’s food also replaces any salt that is lost by diffusion.
8. Clams, crayfishes and aquatic insect larvae are also hyperosmotic regulators with similar
mechanisms.
9. Amphibians that live in water use their skin to transport sodium and chloride; these tissues are
standard laboratory models for ion transport.
C. Fishes Return to the Sea
1. Marine bony fishes maintain salt concentration of body fluids at about one-third that of seawater.
2. They are therefore hypoosmotic regulators, maintaining their body fluids at lower concentration.
3. Modern oceanic bony fishes are descendants of freshwater fishes, returning during the Triassic
period.
4. Their ionic body concentration of about one-third that of seawater is related to their marine heritage.
5. Freshwater fish returning to the sea in the Triassic period lost water and gained salt-it “dried out.”
6. Marine fish therefore drink seawater and it is absorbed in the intestine; salt is carried by blood to
gills.
7. Special salt-secreting cells in the gills transport the salt back to the sea.
8. Ions that remain in the intestine as residue (e.g. magnesium, sulfate, calcium) are voided with feces.
9. A marine fish consumes only enough water to replace water loss.
10. Elasmobranchs (i.e., sharks and rays) achieve the same osmotic balance by a different mechanism;
the urea compounds accumulate in the blood until there is no osmotic difference with seawater.
D. How Terrestrial Animals Maintain Salt and Water Balance (Table 10.1; Figures 26.4, 27.13)
1. Animals carried their watery composition with them as they evolved within a terrestrial existence.
2. They continued to adapt to the threats of desiccation and became abundant in arid areas.
3. Animals lose water across respiratory and body surfaces, excretion of urine and elimination of feces.
4. Water is gained from water in food, drinking water and metabolic water.
5. Some desert arthropods can absorb water vapor from the air.
6. In desert rodents, metabolic water constitutes most of the animal’s water uptake.
7. Water balance in a human and a desert rodent is quite different.
8. Dilution of Wastes
a. The primary end product of protein breakdown is highly toxic urea.
b. Fishes excrete urea across the gills and the abundance of water keeps it dilute.
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
10.2.
10.3.
c. Terrestrial insects, reptiles and birds convert urea to nontoxic uric acid.
d. Uric acid is insoluble and is excreted with little water loss.
e. Uric acid can be stored in harmless crystalline form within an egg until hatching.
9. Marine birds and turtles have a salt gland that secretes concentrated sodium chloride; these are
important accessory glands to the kidneys that only produce very diluted urine.
Invertebrate Excretory Structures (Figure 11.8)
A. Contractile Vacuole
1. These are small, spherical, intracellular vacuoles of protozoa, freshwater sponges, and radiate
animals.
2. They are not truly excretory; ammonia and other nitrogenous wastes diffuse across the cell
membrane.
3. The contractile vacuole is an organ of water balance; it expels excess water that enters by osmosis.
4. A network of channels populated with proton pumps probably surrounds them.
5. Contractile vacuoles are absent in marine forms that are isosmotic with seawater.
B. Protonephridium (Figures 10.5-10.8)
1. This tubular structure is the most common design to maintain osmotic balance.
2. The flame cells system or protonephridium is the simplest arrangement.
3. Planaria and other flatworms have a highly branched duct system to all parts of the body.
4. Fluid enters the system through specialized “flame cells” and passes through tubules to exit the
body.
5. Rhythmical beating of a flagellar tuft creates a negative pressure that draws fluid into the tubes.
6. In the tubule, water and metabolites are recovered by reabsorption; wastes are left to be expelled.
7. Nitrogenous wastes, mainly ammonia, diffuse across the surface of the body.
8. Flatworms have no circulatory system so the flame cell system must branch throughout the animal.
9. This system is a closed system since the fluid must pass across flame cells.
C. Metanephridium
1. A metanephridium is an open system found in molluscs and annelids.
2. The tubule is open at both ends; fluid is swept into the tubule through a ciliated funnel-like opening.
3. A network of blood vessels to reclaim water and valuable solutes surrounds a metanephridium.
4. The basic process of urine formation in the tubule remains the same: withdraw valuable solutes and
add waste solutes.
D. Arthropod Kidneys
1. The Paired Antennal Glands of Crustaceans
a. Located in the ventral part of the head, they are an advanced design of nephridia.
b. They lack open nephrostomes.
c. Hydrostatic pressure of the blood forms a protein-free filtrate in the end sac.
d. In the tubular portion, certain salts are selectively reabsorbed or actively secreted.
e. This crustacean system is similar to the vertebrate system in sequence of urine formation.
2. Malpighian Tubules
a. Insects and spiders use this system in conjunction with rectal glands.
b. The thin, elastic, blind Malpighian tubules are closed and lack an arterial supply.
c. Salts, largely potassium, are actively secreted into portions of the tubule from the hemolymph.
d. Secretion of salt creates an osmotic drag that pulls water, solutes and wastes into the tubule.
e. Uric acid enters the upper end of the tubule as soluble potassium urate and precipitates as
insoluble uric acid in the proximal end of the tubule.
f. When the solution reaches the rectum, rectal glands reabsorb water and potassium.
g. Uric acid and other wastes continue out in the feces.
h. This is an especially efficient system for dry environments.
Vertebrate Kidney (Figure 10.9)
A. Ancestry and Embryology
1. The earliest vertebrate kidney had segmentally arranged tubules similar to an invertebrate
nephridium.
2. Each tubule opened into the coelom at a nephrostome; the other end led into a common archinephric
duct.
3. This ancient kidney is called an archinephros; a similar segmented kidney is in embryos of
hagfishes.
4. From the earliest time, the reproductive system from the same mesoderm used the nephric ducts.
5. Three developmental stages occur in the embryonic development of vertebrate kidneys.
6. The pronephros is observed in vertebrate embryos; it usually degenerates except in hagfish.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
7.
The mesonephros replaces the pronephros and contributes to the adult kidney of fishes and
amphibians.
8. The Metanephros
a. This is found in adult amniotes.
b. It is more caudally located and is much larger and compact.
c. It contains a large number of nephric tubules.
d. The ureter is a new duct that drains the system; the archinephric duct has shifted to sperm
transport.
9. The three stages succeed each other embryologically and phylogenetically in amniotes.
B. Vertebrate Kidney Function (Figures 10.10, 10.11)
1. The vertebrate kidney is the principal organ that regulates volume and composition of internal fluids.
2. The removal of metabolic wastes is incidental to its regulatory function.
3. Urine is formed in the nephron by filtration, reabsorption and secretion.
4. Structure of Human Kidney
a. Kidneys comprise less than one percent of body weight but filter 20-25% of blood output.
b. Blood flows through nearly a million nephrons in each kidney.
c. The nephron begins in the renal corpuscle that contains a tuft of capillaries called the
glomerulus.
d. Blood pressure in capillaries forces protein-free filtrate into a renal tubule.
e. Filtrate passes into a proximal convoluted tubule, the loop of Henle and the distal convoluted
tubule.
f. Collecting ducts join to form the renal pelvis and carry urine through a ureter to the urinary
bladder.
g. Throughout the passage, some solutes are reabsorbed and some are concentrated.
h. The blood from the dorsal aorta enters each kidney through the renal artery.
i. A renal artery branches to an afferent arteriole; they leave the renal corpuscle as efferent
arterioles.
j. Efferent arterioles travel through extensive capillary networks around the proximal and distal
convoluted tubules and the loop of Henle.
k. The capillary network collects to form the renal vein that returns blood to the vena cava.
C. Glomerular Filtration (Figure 10.12)
1. The glomerulus is a specialized mechanical filter.
2. Blood pressure drives a protein-free filtrate across capillary walls into the fluid-filled renal
corpuscle.
3. Smaller solute particles are also carried across if they can fit through the slit pores of capillary walls.
4. Red blood cells and plasma proteins are too large to pass across.
5. The filtrate will undergo extensive modification before becoming urine.
6. About 180 liters (50 gallons) of filtrate form each day; most is reabsorbed and 1.2 liters of urine
form.
D. Tubular Reabsorption (Figure 10.13)
1. About 60% of filtrate volume and nearly all glucose, amino acids, and vitamins are reabsorbed in the
proximal convoluted tubule.
2. Most reabsorption is by active transport; unique ion pumps retrieve sodium, calcium, potassium, etc.
3. Water passively follows the osmotic gradient with active reabsorption of solutes.
4. For most substances, there is an upper limit to reabsorption (transport maximum or renal threshold).
5. Normally there is no glucose in urine because the transport maximum is well above the glucose
level.
6. A kidney filters 600 grams of sodium a day and retrieves 596 grams, excreting 4 grams.
7. If human intake of sodium is higher than 4 grams, excess sodium may build in tissues and cause
problems.
8. The distal convoluted tubule carries out final adjustment of filtrate composition.
9. About 85% of sodium absorbed by the proximal convoluted tubule is obligatory or set.
10. In the distal convoluted tubule, sodium reabsorption is controlled by aldosterone.
11. Aldosterone increases active reabsorption of sodium in distal tubules and decreases loss of sodium.
12. Secretion of aldosterone is regulated by the enzyme renin, produced by the juxtaglomerular
apparatus, a complex of cells located in the afferent arteriole at its junction with the glomerulus.
(Figure 32.10)
13. Renin is released in response to low blood sodium level or low blood pressure.
14. Renin initiates a series of enzymes that result in production of angiotensin, a blood protein.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
10.4.
15. Angiotensin stimulates release of aldosterone, which increases sodium reabsorption in the distal
tubule.
16. Angiotensin also increases secretion of antidiuretic hormone (vasopressin) that promotes water
conservation by the kidney.
17. Angiotensin increases blood pressure and stimulates thirst.
18. These actions reverse the circumstances that triggered the secretion of renin: sodium and water are
conserved, and blood volume and pressure return to normal.
19. Selective pressure has restricted sodium levels in humans while sodium range is broad in rodents.
E. Tubular Secretion
1. The nephron also secretes materials into the filtrate, the reverse of tubular reabsorption.
2. Carrier proteins in tubular epithelial cells selectively transport substances from blood to tubule.
3. This allows a build up of urine concentrations of hydrogen and potassium ions, drugs, etc.
4. Most tubular secretion is at the distal convoluted tubule.
5. Marine fishes, reptiles and birds use tubular secretion far more than do mammals.
6. Marine bony fishes actively secrete large amounts of magnesium and sulfate from seawater salts.
7. Uric acid is actively secreted by the tubular epithelium.
F. Water Excretion (Figures 10.14, 10.15)
1. The kidney closely regulates the osmotic pressure of the blood.
2. When fluid intake is high, the kidney excretes dilute urine and saves salts.
3. When fluid intake is low, the kidney conserves water and forms concentrated urine.
4. A dehydrated person can concentrate urine to approximately four times blood osmotic concentration.
5. Countercurrent Multiplication
a. Mammal and bird kidneys produce concentrated urine by interaction between the loop of Henle
and the collecting ducts.
b. This forms an osmotic gradient in the kidney.
c. In the cortex, the interstitial fluid is isosmotic with the blood.
d. Deep in the medulla, the osmotic concentration is four times greater than that of the blood.
e. High osmotic concentrations in the medulla are produced by an exchange of ions in the loop of
Henle.
f. “Countercurrent” refers to the opposite directions of the loop of Henle, down the descending
limb and up the ascending limb.
g. “Multiplication” describes the increasing osmotic concentration in the medulla from ion
exchange between the two limbs.
h. The descending limb of the loop of Henle is permeable to water but impermeable to solutes.
i. The ascending limb of the loop of Henle is impermeable to both water and solutes.
j. Sodium chloride is actively transported out of the thick portion of the ascending limb and into
surrounding tissue.
k. As the interstitial area surrounding the loop becomes concentrated, water is withdrawn from the
descending limb by osmosis.
l. Tubular fluid at the base of the loop is more concentrated and moves up the ascending limb
where more sodium is pumped out.
m. The effect of active ion transport in the ascending limb is multiplied as more water is withdrawn
from the descending limb and more concentrated fluid is presented to the ascending limb ion
pump.
6. Because of high concentration of solutes surrounding a collecting duct, water is withdrawn from
urine.
7. As urine becomes concentrated, urea diffuses out, adding to a high osmotic pressure in the kidney
medulla.
8. The amount of water reabsorbed depends on the permeability of the walls of the distal convoluted
tubule.
9. This is controlled by antidiuretic hormone (ADH, or vasopressin) released by the posterior pituitary.
10. ADH increases the permeability of the collecting duct and water diffuses outward.
11. In overhydration, the pituitary stops releasing ADH, pores in duct walls close, and more urine is
excreted.
Temperature Regulation
A. Chemical Environment
1. Biochemical activities are sensitive to temperature because enzymes have an optimum temperature.
2. Temperature constraints on animals are due to their need to maintain biochemical stability.
3. At colder temperatures, metabolic reactions may be too slow to maintain activity and reproduction.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
4. At too high temperatures, enzyme activity is impaired or destroyed.
5. Generally animals function between 0o and 40o C.
6. Animals may locate such habitats or develop means to stabilize their metabolism.
B. Ectothermy and Endothermy
1. “Cold-blooded” and “warm-blooded” are not well-defined terms; fishes, insects, and reptiles basking
in the sun may be warmer than mammals.
2. Many “warm-blooded” mammals hibernate and approach very cold temperatures.
3. “Poikilothermic” refers to a variable body temperature, and “homeothermic” refers to maintaining a
constant body temperature; these terms likewise pose definition problems.
4. All animals produce some heat from cellular metabolism.
5. In ectotherms, the heat is conducted away as fast as it is produced.
6. Many ectotherms may behaviorally select areas of more favorable temperature, such as basking in
the sun.
7. Endotherms are able to generate enough heat to elevate their own temperature to a high and stable
level.
8. Birds and mammals are the commonly recognized endotherms.
9. Some reptiles and fast-swimming fishes, and at times certain insects, may also be endotherms.
10. Endothermy allows birds and mammals to stabilize internal biochemical processes and nervous
system functions.
11. Endotherms can also remain active in winter and exploit habitats denied to ectotherms.
C. How Ectotherms Achieve Temperature Independence (Figure 10.16)
1. Some ectotherms behaviorally regulate body temperature.
2. Desert lizards exploit hour-to-hour changes in solar radiation.
3. In cool mornings, they bask with bodies flattened; in the hottest daytime, they retreat to burrows.
4. Such lizards hold body temperature between 36o and 39o while the environment varies from 29o to
44o C.
5. Metabolic Adjustments
a. Within limits, most ectotherms can adjust metabolic rate to the prevailing temperature.
b. Temperature compensation involves complex biochemical and cellular adjustments.
c. This process allows a fish or salamander to sustain the same level of activity in warm or cold
water.
D. Temperature Regulation in Endotherms (Figure 10.17)
1. Most mammals have body temperatures between 36o and 38o C; most birds range from 40o to 42o C.
2. Much of an endotherm’s daily caloric intake goes to generate heat; it must eat more than an
ectotherm.
3. Heat is lost by radiation, conduction and convection to a cooler environment, and by evaporation of
water.
4. If an animal becomes too cool, it can generate heat by exercise or shivering, and decrease heat loss
by increasing insulation.
5. Adaptations for Hot Environments (Figure 10.18)
a. Small desert animals are often fossorial, living in the ground, or nocturnal, active at night.
b. Lower temperatures and higher humidity of burrows also reduces water loss from evaporation.
c. Desert animals may also drink no water, but derive all water from food and produce dry feces.
d. The desert eland has many adaptations for desert living: glossy, pallid fur; fur insulation; fat
tissue isolated on the back; and dropping body temperature at night.
e. When the body temperature reaches 41o C, it uses evaporative cooling by sweating and
panting.
f. The desert camel has all of these adaptations perfected for desert living.
6. Adaptations for Cold Environments (Figure 10.19)
a. Mammals and birds use decreased conductance and increased heat production to survive the
cold.
b. In winter, fur may increase in thickness by 50%.
c. Countercurrent Heat Exchange
1) A well-insulated body can lose substantial heat through blood flowing along exposed limbs.
2) Arterial blood in the leg of an arctic mammal or bird passes in contact with returning cold
blood.
3) The heat exchange all along the opposite vessels transfers nearly all body heat to the
returning venous blood that returns to the body core.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
4) Similar countercurrent exchange systems keep aquatic mammal flippers from losing body
heat.
5) Footpads and hooves must be able to operate at near-freezing temperatures.
d. Augmented muscular activity increases heat by exercise or shivering.
e. Nonshivering thermogenesis uses increased oxidation of stores of brown fat.
f. Small mammals live in the milder climate under the snow, a subnivean environment.
E. Adaptive Hypothermia in Birds and Mammals (Figures 10.20, 10.21)
1. The endotherm must always have an energy supply to support its high metabolic rate.
2. Small birds and mammals have an intense metabolism that is difficult to support on cold nights.
3. Daily torpor is dropping body temperature when asleep or inactive; it prevents energy loss.
4. Hummingbirds may drop body temperature at night when food supplies are low.
5. Hibernation is prolonged and controlled dormancy.
6. True hibernators prepare for winter by storing body fat.
7. Entry into hibernation is gradual; the animal eventually cools to near ambient temperature.
8. Respiration may drop from 200 breaths per minute to 4-5 per minute; heart rate from 150 to 5 beats
per minute.
9. Arousal from hibernation may require shivering and nonshivering thermogenesis.
10. Bears, badgers, raccoons and opossums enter a prolonged sleep with little or no decrease in body
temperature.
11. This prolonged sleep is not true hibernation; the animal can be awakened if disturbed.
Lecture Enrichment
1.
2.
3.
4.
The human systems are explained in this and the following chapters since the human system is the most familiar
to students and therefore is more “meaningful”; however, care must be given to prevent viewing the human as
“typical” or “representative” of animals in general, since we are neither.
The human kidney was one of the first major organs to be transplanted. When describing the gross anatomy of
the kidney, note the clear encapsulation and the limited blood vessels and ureters that make this a simple organ to
transplant relative to the liver, for instance.
The complex of filtrations and absorptions involved in kidney function require both visuals and a logical sequence
of concept descriptions. The relationship of kidney function to blood pressure is difficult to explain since students
have not yet studied the circulatory system and blood pressure.
Careful and more-refined use of terms is encountered in both the discussion of regulation of body temperatures
and hibernation. It is important for the instructor to be consistently correct.
Commentary/Lesson Plan
Background: Students may have family members who take blood pressure medicine that is diuretic; this chapter’s
concepts should clarify why blood volume and viscosity are important factors on blood pressure, the extent the heart
must work to circulate the blood and why changing kidney function can relieve the heart.
Misconceptions: We culture children to think of urine as “yucky” and associated with feces as a source of disease;
the fact that this is a system that filters blood and that urine is sterile unless there is an infection present, will not
counteract this social attitude unless directly discussed.
Schedule:
HOUR 2 10.3. Vertebrate Kidney
HOUR 1 10.1. Water and Osmotic Regulation
A. Ancestry and Embryology
A. Marine Invertebrates Meet Problems
B. Vertebrate Kidney Function
of Salt and Water Balance
C. Glomerular Filtration
B. Freshwater Invasion
D. Tubular Reabsorption
C. Fishes Return to the Sea
E. Tubular Secretion
D. Terrestrial Animals Maintain Salt and
F. Water Excretion
Water Balance
10.4. Temperature Regulation
10.2. Invertebrate Excretory Structures
A. Chemical Environment
A. Contractile Vacuole
B. Ectothermy and Endothermy
B. Protonephridium
C. Ectotherms Achieve Temperature
C. Metanephridium
Independence
D. Arthropod Kidneys
D. Temperature Regulation in
Endotherms
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
E. Adaptive Hypothermia in Birds and
Mammals
ADVANCED CLASS QUESTIONS:
1. Why can the brackish-water crab withstand a wide variation in salinity while the marine spider crab is intolerant
of any change in salinity?
2. Why would a marine fish that needs to hold onto freshwater, be so careful to only take in as much water as
necessary to reach its normal body salinity, and absolutely no more?
3. If 180 liters of filtrate is produced but only 1.2 liters are excreted as urine, what percent of filtrate is excreted?
4. Why would a healthy person sometimes have concentrated urine and at other times have dilute urine?
5. How does the length of the loop of Henle correlate with the ability of animals to concentrate urine?
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Twelfth Edition Changes: Minor changes were made in this chapter and these are listed below:
1.
2.
3.
4.
5.
6.
Systems within an organism function in an integrated way to maintain a constant internal environment around
a setpoint.
Stored fat becomes an important source of metabolic water in diving mammals.
A figure of the kangaroo rat showing water balance mechanisms will be included with Table 10.1.
A more in-depth discussion of Bowman’s capsule and the renal corpuscle is included under the vertebrate
kidney function section.
The blood capillaries surrounding the lopps of Henle, the vasa recta, are also arranged in a countercurrent
fashion.
The buildup of urea contributes significantly to high osmotic concentration of the medulla.
Source Materials
[Bold = recommended; vendor abbreviations are provided in Appendix 1]
ABGAME (C-E-G), MS-DOS
ABASE: A Program for Teaching Acid Base Regulation (C-BE), Mac
A.D.A.M. Essentials: A Multimedia Exploration of the Human Body (CAM) (INT), Mac CD
A.D.A.M. Interactive Anatomy (ADAM) (SciT) Mac, MS-DOS
Anatomist 2.1 (CSG), Mac
Anatomist (CBSC), Mac CD
Biomedical Software: Anatomy and Physiology (PLP), 8 software products, Apple
Blood (FH), 23-min. video
Blood: The Microscopic Miracle (EBE), 22-min. video
The Body Atlas (AVP) (JLM), 13 25-min. videos
Body and Mind (Q), MS-DOS CD
The Body Electric (CBSC), Apple
Body Language (CBSC), Mac, MS-DOS
Body Language: Urinary System (PLP), Apple, MS-DOS or Mac
Body Language: Study of Human Anatomy 7-Part Series (PLP), Apple, MS-DOS
BodyWorks 3.0 (IM), MS-DOS and Mac CD
BodyWorks 4.0—Human Anatomy Leaps to Life (Q), Mac or MS-DOS CD
Bones and Muscles (IFB), 15-min. video
CatWorks (CAM), Mac, Win CD [anatomy]
Clinical Pharmacology (SciT) Win, Mac
Comparative Histology (BDI), Mac and MS-DOS CD or Laserdisc
Comprehensive Review in Biology: Digestion and Excretion (Q), Mac, Win
Cycles of Life: Exploring Biology–Digestion and Fluid Balance (A-CPB), 30-min. video
Cycles of Life: Exploring Biology–Endocrine Control: Systems in Balance (A-CPB), 30-min. video
Evolution of the Vertebrate Kidney (ei), slides
Excretion (IM), 29-min. video
Excretory System (IM), 19-min. video
Experiments in Human Physiology (CBSC), Apple II
Explorations in Human Anatomy and Physiology (CBSC), Mac, MS-DOS CD
Explorations in Human Biology (CBSC) (Q), Mac, MS-DOS CD
The Feedback Cycle (FH), 10-min. video
Graphic Human Anatomy and Physiology Tutor: Urinary System (PLP), MS-DOS
Growing Old in a New Age–How the Body Ages (A-CPB), 1-hr. video
Growing Old in a New Age–Illness and Disability (A-CPB), 1-hr. video
A History of Medicine (Q), Win CD
Homeostasis (HRM), filmstrip
Homeostasis (IM), 30-min. video
Homeostasis (WARDS), 6 10-min. videos
Homeostasis: Maintaining the Body’s Environment (IM), 30-min. video
Homeostasis: Maintaining the Body's Internal Environment (HRM), filmstrip or video
Homeostasis Series (6-part series) (FH), 10-min. each video
Human Biology (FH), 58-min. video or videodisc
Human Biology (Q), Mac or MS-DOS CD
The Human Body (Q) (SciT), MS-DOS CD
The Human Body Series: Excretory System (PHO), 14-min. video
288
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Human Pathology (BDI) Mac and MS-DOS CD or laserdisc
Human Physiology Data Simulation (OAK), MS-DOS, Mac
Iliad (SciT) Win, Mac [diagnosis of diseases]
The Incredible Human Machine (Fish) (NGS), 57-min. video
Incredible Voyage (CRM), 26-min. video
InnerBodyWorks (CSG), Mac
Integument, The (IM), 29-min. video
Introduction to Human Tissues (JLM), slide set (20)
Introduction to the Body: Landscapes and Interiors (FH), 26-min. video
Introduction to General Biology: The Human Body I (Q), Mac, DOS
Introduction to General Biology: The Human Body II (Q), Mac, DOS
Introduction to Human Tissues (JLM), slide set (20)
Human Biology (Q), Mac or MS-DOS CD
The Human Body (Q), MS-DOS CD
The Human Body: Structure and Function (INT), Mac
Human Pathology (BDI) Mac and MS-DOS CD or Laserdisc
Human Physiology Data Simulation (OAK), MS-DOS and Mac
InnerBodyWorks (CSG), Mac
Kidney (PLP), Apple
Kidney Functions (AIMS), Mac, Win CD, 5-min. video, laserdisc
The Kidney and Homeostasis (BSCS Classic Inquiry) (MDA), videodisc
The Living Body (CBSC) (FH), 26-part series, 26-28-min. video or videodisc
Looking Into the Body (PHO), 33-min. video
MacHomeostasis (PLP), MS-DOS
Mammalian Kidney (ei), slides
The Mammalian Kidney (Biology: Form and Function) (CPB) (IM), 24-min. video
The New Living Body (FH), 10 20-min. videos
NOVA: The Brutal Craft (WGBH), 55-min. video
NOVA: Fat in a Thin World (WGBH), 55-min. video
NOVA: MD: The Making of a Doctor (MBI) (NEB) (WGBH), 120-min. video
NOVA: The Universe Within (JLM) (NEB), 60-min. video
Osmoregulation (FH), 10-min. video
An Overview of Human Anatomy: Head and Torso (NEB), 40-min. video [dissection]
Oxford Textbook of Medicine (Second Edition), Electronic Edition (OX), MS-DOS CD
Oxford Textbook of Surgery (Q), Win CD
The Oxford Textbook of Surgery on CD-ROM (OX), MS-DOS CD
Physiological Data Simulation (OAK), MS-DOS and Mac
Physiology of the Kidney (PH), 7-min. video
Powers of Ten (PYR), 10-min. video
Problems in Fluid Compartment Re-Distribution (C-BE), MS-DOS
The Renal System [Simulations in Physiology] (NRCLSE), MS-DOS and Mac
Respiration and Waste (WARDS), 8-min. video
Review of Biology: Design for Living (FH), 26-min. video
Stress Physiology Data Simulation (OAK), MS-DOS and Mac
The Systematic Body (INT), Mac
Systems of the Body: An Introduction (ei), filmstrip
Tissues (IM), 29-min. video
Understanding Human Physiology 4-Part Series (PLP), MS-DOS
Urinary System and Its Function (ei), slides
The Urinary Tract: Water (FH), 26-min. video
The Ultimate Human Body (CBSC) (Fish), Mac, MS-DOS CD
The Videodisc Encyclopedia of Medical Images (FH) MS-DOS-driven videodisc
Virtual Anatomy's 3D Skeletal (SciT) Win, Mac
WARD's Epithelial Cells Smart Slides (WARDS), Mac, Win CD
WARD's Histology Collection (WARDS), Mac, Win CD
Water (FH), 26-min. video
The Work of the Kidneys (EBE), 29-min. video
Work of the Kidneys (IM), 23-min. video
289
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
CHAPTER
11
INTERNAL FLUIDS AND RESPIRATION
CHAPTER OUTLINE
11.1.
11.2.
Internal Fluid Environment (Figures 11.1, 11.2)
A. Fluids
1. Body fluid of a single-celled organism is cellular cytoplasm.
2. In multicellular organisms, body fluids are intracellular and extracellular.
3. Intracellular fluids are the collective fluids inside all the body’s cells.
4. Extracellular fluids are outside and surrounding the cells.
5. Extracellular fluid buffers cells from harsh physical and chemical changes outside the body.
6. In vertebrates, annelids and a few others, extracellular fluid is further divided into blood plasma and
interstitial fluid.
7. Blood vessels contain the plasma while interstitial fluid is between the cells and organs of the body.
8. Nutrients and gases passing between vascular plasma and cells must traverse this fluid separation.
9. Interstitial fluid is constantly formed from plasma by filtration through capillary walls.
B. Composition of the Body Fluids
1. Plasma, interstitial and intracellular fluids are mostly water.
2. Animals range from 70% to 90% water.
3. Humans are 70% water by weight; 50% is cell water, 15% is interstitial and 5% is blood plasma.
4. Plasma is the pathway of exchange between cells and the kidney, lung or gill, and alimentary canal.
5. Body fluids contain many inorganic and organic substances in solution.
a. Sodium, chloride and bicarbonate are the chief extracellular electrolytes.
b. Potassium, magnesium, and phosphate ions and proteins are major intracellular electrolytes.
c. Concentrations are maintained despite continuous flow of materials into and out of cells.
6. Plasma and interstitial fluids have similar composition except that plasma has more large proteins.
Composition of the Blood (Figures 11.3, 11.4)
A. Elements
1. Flatworms and cnidarians lack a circulatory system and do not have a true “blood.”
2. Invertebrates with an open circulatory system have a more complex “hemolymph.”
3. Closed circulatory systems keep blood contained in blood vessels separate from tissue fluids.
4. In vertebrates, blood is a complex liquid tissue of formed elements suspended in plasma.
5. When separated by centrifugation, blood is 55% plasma and 45% formed elements.
6. Plasma
a. Water constitutes 90%.
b. Dissolved solids include plasma proteins (e.g. albumin, globulins, fibrinogen), glucose, amino
acids, electrolytes, various enzymes, antibodies, hormones, metabolic wastes, etc.
c. Dissolved gases include oxygen, carbon dioxide and nitrogen.
7. Formed Elements
a. Red blood cells contain hemoglobin and transport oxygen and carbon dioxide.
b. White blood cells are scavengers and defend the body against foreign material.
c. Cell fragments function in blood coagulation.
8. Plasma proteins are a diverse group with many functions.
a. Albumins are 60% of plasma proteins and help maintain osmotic equilibrium.
b. Globulins are high-molecular weight proteins and include immunoglobulins.
c. Fibrinogen is a very large protein that is involved in clot formation.
d. Blood serum is plasma minus the proteins.
9. Red Blood Cells (Erythrocytes)
a. Red blood cells occur in enormous numbers in the blood.
b. In mammals and birds, they form from large, nucleated erythroblasts in red bone marrow.
c. In other vertebrates, kidneys and spleen are the major sites of red blood cell production.
d. In mammals, the nucleus shrinks and disappears during development.
e. Human red blood cells also lose ribosomes, mitochondria and most enzyme systems.
f. The human cell is biconcave in shape; this provides the greatest surface area for gas diffusion.
g. Each cell holds about 280 million molecules of hemoglobin.
h. About 33% of the weight is hemoglobin.
i. In non-mammal vertebrates, red blood cells have a nucleus and are ellipsoidal.
j. Erythrocytes have an average life of four months and may travel 11,000 kilometers.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
11.3.
k. When it is worn out and fragments, it is engulfed by macrophages in the liver.
l. Iron from hemoglobin is salvage and used again.
m. The rest of the heme molecule is converted to bilirubin, a bile pigment.
n. About 10 million erythrocytes are destroyed every second, and that number must be replaced.
10. White Blood Cells (Leukocytes)
a. White blood cells provide a wandering system of protection for the body.
b. In human adults, they number about 7.5 million per milliliter of blood, about one per 700 RBCs.
c. Varieties include: granulocytes (neutrophils, basophils, and eosinophils) and agranulocytes
(lymphocytes and monocytes).
B. Hemostasis; Prevention of Blood Loss (Figures 11.5, 11.6)
1. Blood flows under considerable hydrostatic pressure; it is important to prevent blood loss after
injury.
2. When a vessel is damaged, smooth muscle in the wall of the vessel contracts and the lumen narrows.
3. In both vertebrates and invertebrates, this constriction may totally prevent blood loss.
4. Vertebrates and larger, active invertebrates have special cellular elements to form clots.
5. Blood coagulation is the dominant hemostatic defense in vertebrates.
6. Blood clots form as a tangled network of fibers from one of the plasma proteins, fibrinogen.
7. Transformation of fibrinogen into a fibrin meshwork is catalyzed by the enzyme thrombin.
8. Thrombin is present in the blood in the inactive form prothrombin.
9. Platelets
a. Platelets form in red bone marrow from large cells that pinch off bits of cytoplasm.
b. Platelets are fragments of cells; there are about 150,000 to 300,000 per cubic millimeter of
blood.
c. Platelets adhere to any disruption in the normally smooth inner surface of a blood vessel.
d. They release thromboplastin and other clotting factors.
e. These factors and calcium ions initiate conversion of prothrombin to active thrombin.
f. This involves a long and complex catalytic sequence; each reactant cascades into release of
much more of the next reactant.
g. 13 different plasma coagulation factors are known; a deficiency of one factor can stop the
process.
h. This provides a balance between providing emergency clotting and avoiding unnecessary clots.
10. Hemophilia is one of several clotting abnormalities; it is caused by a mutation on the X
chromosome.
Circulation (Figure 11.7)
A. General Design
1. Sponges and ciliates utilize the water medium around them for transport.
2. Flattened animals can utilize diffusion across their thin surfaces, but only to a limit.
3. Larger animals cannot rely on diffusion to support respiratory and metabolic needs.
4. A full circulatory system has a propulsive organ, arteries, capillaries and a venous reservoir.
5. An earthworm demonstrates this basic system with a distributed pumping system.
B. Open and Closed Circulations (Figure 11.8)
1. A closed circulatory system confines blood to a journey through the vascular system.
2. An open circulation system lacks connecting blood vessels and capillaries.
3. In arthropods, molluscs and some other invertebrates, sinuses collectively form the hemocoel.
4. Open System
a. During development, the blastoderm is not filled by mesoderm but becomes the hemocoel.
b. The blood or hemolymph washes through this primary body cavity or hemocoel.
c. There is no distinction between blood plasma and lymph, as is the case in closed circulation.
d. Hemolymph is 20-40% of body volume in open systems; blood is 5-10% in closed systems.
e. In arthropods, the heart and all organs lie in the hemocoel bathed by blood.
f. Blood enters the heart through valved openings to the side or ostia.
g. Forward-moving waves propel blood forward to the head where it washes into the hemocoel.
h. It is routed through the body by baffles and membranes before returning back into the heart
ostia.
i. Blood pressure is very low in open systems, rarely over 4-10 mm Hg.
j. Therefore, arthropods have auxiliary hearts or contractile vessels to boost blood flow.
5. Closed Systems
a. In embryonic development of animals with closed systems, the coelom increases to obliterate
the blastocoel and forms a second body cavity.
b. The system of continuously connected blood vessels develops within the mesoderm.
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
c.
d.
e.
f.
g.
The heart pumps blood into arteries that branch into arterioles that enter a vast capillary system.
Blood leaves the capillaries in converging venules and larger veins to return to the heart.
Capillary walls are thin to allow transfer of materials between blood and tissues.
Such a closed system allows large animals to shunt blood to tissues needing it.
However, blood pressure is much higher in closed systems; fluid is pushed across capillary
walls.
h. Fluid lost into tissues and interstitial spaces is returned by osmosis and the lymphatic system.
C. Plan of Vertebrate Circulatory Systems (Figures 11.9-11.12)
1. Comparative Anatomy
a. The principal difference in vertebrate systems is the separation of the heart into two pumps.
b. These changes occurred as vertebrates converted from gill breathing to lungs.
c. The Fish Heart
1) The heart has two main chambers in series: the atrium and ventricle.
2) The atrium is preceded by an enlarged sinus venosus that collects blood and smooths
delivery.
3) Blood makes one circuit, flowing first to gills and then on to the aorta and body.
4) Oxygenated blood is provided to the body organs before the veins return to the heart.
5) However, gill capillaries offer much resistance, and blood pressure to the body tissues is
low.
d. Double Circulation
1) Terrestrial animals evolved lung breathing and eliminated gills between heart and aorta.
2) This provided a high pressure system that provided oxygenated blood to capillary beds and
a pulmonary circuit to serve the lungs.
3) This change is seen in lungfishes and amphibians.
4) Modern amphibians have separate atria.
5) The right atrium receives venous blood from the body.
6) The left receives oxygenated blood from the lungs.
7) The ventricle is undivided but venous and arterial blood do not heavily mix.
8) Ventricles are nearly separate in crocodilians and completely separate in birds and
mammals.
9) Systemic and pulmonary circulations are served by one half of a dual heart.
2. Mammalian Heart (Figures 11.13, 11.14)
a. The mammalian heart is located in the thorax and enclosed in the pericardial sac.
b. Blood returning from the lungs collects in the left atrium and passes to the left ventricle.
c. The left ventricle pumps the blood to the body in the systemic circuit.
d. Blood returns from the body into the right atrium and passes to the right ventricle.
e. The right ventricle pumps the blood to the lungs in the pulmonary circuit.
f. The bicuspid valves are between the left atrium and ventricle to prevent backflow of blood.
g. The tricuspid valves separate the right atrium and right ventricle to prevent backflow of blood.
h. Semilunar valves stop backflow from the pulmonary to right ventricle and aorta to left ventricle.
i. Contraction of the heart is systole.
j. Relaxation of the heart is diastole.
k. When the atria contract, the ventricles relax; ventricular systole is accompanied by atrial
diastole.
l. Cardiac output is the amount of blood moved through the heart; exercise can increase it fivefold.
m. Heart rates can vary from an ectothermic codfish at 30 beat per minute to a rabbit at 200.
n. Smaller animals have a faster heart rate than larger animals: an elephant has 25, a human has 70,
a cat has 125, a mouse has 400 and a tiny shrew has 800 beats per minute.
3. Excitation of the Heart
a. The vertebrate heart is a muscular pump composed of cardiac muscle.
b. Cardiac muscle fibers are branched and striated, but do not depend on nerve activity to contract.
c. Specialized pacemaker cells initiate nerve contractions.
d. In the tetrapod heart, the pacemaker is the sinus node, a remnant of the sinus venosus in fish.
e. Electrical activity of the pacemaker spreads over the muscle of the two atria and then the muscle
of the ventricles.
f. Electrical activity is conducted through the atrioventricular bundle to the apex of the ventricle
and then continues through the specialized Purkinje fibers up the ventricle walls.
g. This causes the contraction to begin at the tip and squeezes blood out efficiently at the same
time.
h. A control (cardiac) center in the medulla sends out two sets of nerves.
Fondamenti di zoologia
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Copyright © 2005 – The McGraw-Hill Companies srl
1) Impulses sent along the vagus nerves brake the heart rate.
2) Impulses sent along the accelerator nerves speed up the heart rate.
3) Both terminate at the sinus node for direct guidance of the pacemaker.
i. The cardiac center receives sensory information from pressure and chemical receptors.
j. Myogenic hearts in vertebrates, molluscs, etc. have heartbeat initiated in specialized muscle
cells.
k. In a neurogenic heart, as is found in decapods, a cardiac ganglion serves as a pacemaker and
the heart stops beating without this stimulation.
l. Isolated myogenic hearts continue to beat for hours; neurogenic hearts do not.
4. Coronary Circulation
a. A constantly active heart needs a generous blood supply.
b. Amphibian hearts are heavily channeled; the heart’s pumping action suffices to provide oxygen.
c. Bird and mammal hearts are thicker and need a dedicated vascular supply (coronary
circulation).
d. Coronary arteries divide into an extensive capillary network.
e. Heart muscle has a high oxygen demand and uses 70% of the oxygen from the blood.
f. When the heart is working hard during exercise, the blood supply must increase up to nine
times.
g. Partial or complete blockage of circulation will cause heart cells to die from lack of oxygen.
D. Arteries (Figure 11.15)
1. All vessels leaving the heart are arteries.
2. Arteries must withstand high, pounding pressures and have thick, elastic walls.
3. The wall bulges during systole and compresses the fluid column during ventricular diastole.
4. The next heartbeat surges the blood pressure before it drops to zero.
5. Blood pressure varies between systole and diastole: 120 mm Hg over 80 mm Hg in humans, or
120/80.
6. Arteries branch into narrower arterioles with smooth muscle walls.
7. Arterioles can dilate or constrict diverting blood flow to body organs where it is most needed.
8. Blood pressure is measured as the force required to support a column of mercury.
9. A sphygmomanometer compresses arteries in the upper arm; pressure is released until blood spurts
through under systolic pressure; when pressure drops below diastolic, blood flow is no longer heard.
E. Capillaries (Figures 11.16, 11.17)
1. Structure
a. Marcello Malpighi confirmed capillaries existed in 1661 by inspecting living frog lung tissue.
b. Huge numbers of capillaries infuse most tissues; muscle has over a million per square inch.
c. At rest, fewer than one percent are open; during exercise, all capillaries may be open.
d. Capillaries are extremely narrow, averaging about 8 micrometers in diameter in mammals.
e. Red blood cells are almost this wide and must pass through single-file.
f. Capillary walls are composed of a single layer of endothelial cells held together by a basement
membrane.
2. Capillary Exchange
a. Blood pressure forces fluids out through the permeable capillary walls into interstitial spaces.
b. Plasma protein molecules are too large and the filtrate is nearly protein-free.
c. Fluid exchange across a capillary wall is a balance of hydrostatic pressure and osmotic pressure.
d. If fluids leave the capillaries and do not reenter circulation, the tissues accumulate fluid
(edema).
e. In a capillary, blood pressure is higher at the arteriole end and declines toward the venule side.
f. However, osmotic pressure is created by proteins that cannot pass across the capillary wall.
g. As a result, water and solutes are filtered out at the arteriole end and drawn in at the venule end.
h. However, outflow exceeds inflow and the excess fluid is lymph that remains in interstitial
spaces.
i. This excess is removed by lymph capillaries and eventually returned to the circulatory system.
F. Veins
1. Venules and veins are thinner walled, less elastic, and larger than arteries and arterioles.
2. Blood pressure is low (10 mm Hg) where capillaries drain into venules and nearly zero at the heart.
3. Venous blood is assisted back to the heart by valves in veins, body muscles surrounding veins, and
movement of the lungs.
4. Blood would pool in the long extremities without the veins to segment the blood column.
5. Skeletal muscle action squeezes the veins, and valves keep the flow going toward the heart.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
6.
11.4.
Negative pressure in the thorax, created by breathing, speeds venous return by sucking blood up the
large vena cava.
G. Lymphatic System (Figure 11.18)
1. Thin-walled vessels extend into most body tissues to collect lymph.
2. Lymphatic vessels merge into larger vessels that drain into veins in the lower neck.
3. Lymph has a lower concentration of protein but carries some fat molecules absorbed from the gut.
4. Lymph nodes are located along the lymph vessels and trap and remove foreign particles.
5. Lymph nodes are also a center, along with bone marrow and thymus gland, for lymphocytes.
Respiration
A. Processes
1. Cellular respiration is defined as the oxidative processes that occur inside a cell.
2. External respiration is an exchange of oxygen and carbon dioxide between organism and
environment.
3. Gas exchange by diffusion alone is possible for very small organisms less than one millimeter thick.
4. A flat organism can also present a larger surface area for a volume of body tissue.
5. Because gases diffuse too slowly through tissues, a circulatory system is necessary for deep tissues.
6. Solubility of oxygen in blood plasma is low and plasma alone cannot meet metabolic demands.
7. Special oxygen-transporting proteins such as hemoglobin increase oxygen-carrying capacity.
B. Problems of Aquatic and Aerial Breathing
1. Water and land are vastly different in their physical characteristics.
2. Air contains about 20 times more oxygen than does water; fully saturated water contains 9 ml of
oxygen per liter compared to 209 ml of oxygen per liter in air.
3. Water is 800 times more dense and 50 times more viscous than air.
4. Gas molecules diffuse about 10,000 times more rapidly in air than in water.
5. Advanced fishes still must use up to 20% of their energy to extract oxygen from water.
6. Mammals use only 1-2% of their resting metabolic energy to breathe.
7. Respiratory surfaces must be thin and moist; this is not a problem for aquatic animals.
8. Air breathers have respiratory surfaces invaginated, and pumping actions move air in and out.
9. Evaginations of the body surface, such as gills, are used for aquatic respiration.
10. Invaginations such as tracheae and lungs are used for air breathing.
C. Respiratory Organs
1. Gas Exchange by Direct Diffusion
a. Protozoans, sponges, cnidarians and many worms use direct diffusion to exchange gases.
b. Cutaneous respiration is not sufficient if the body exceeds 1 mm in diameter.
c. However, flatworms extend a thin body to achieve adequate gas exchange.
d. Larger animals can use cutaneous respiration as a supplement to gills or lungs.
e. Eels secure 60% of their oxygen and carbon dioxide exchange through highly vascular skin.
f. During winter hibernation, frogs and turtles can meet their lowered respiratory requirements.
g. Lungless salamanders usually lack lungs as adults; they are limited in body size.
2. Gas Exchange Through Tubes (Figure 11.19)
a. Insects and some other arthropods have a direct and efficient system of tracheae.
b. Air enters through valve-like spiracles.
c. Tracheal channels narrow to fluid-filled tracheoles 1 micrometer in diameter embedded in
tissues.
d. Oxygen diffuses in along a gradient as oxygen is absorbed by tissues.
e. Carbon dioxide diffuses out along a gradient as carbon dioxide builds up in tissues.
f. Some insects ventilate the tracheal system with body movements.
g. The tracheal system is independent of the hemolymph that has no direct role in respiration.
3. Efficient Exchange in Water (Figure 11.20)
a. Gills may be simple external extensions of the body surface (e.g., dermal papulae of sea stars or
branchial tufts of marine worms).
b. Internal gills of fishes and arthropods are thin filamentous structures supplied with vessels.
c. In gills, blood flow is opposite the flow of water to provide the maximum extraction of oxygen;
this is countercurrent flow.
d. Water is washed over the gills in a steady stream, pulled and pushed by an efficient, two valved,
branchial pump.
e. The fish’s forward movement through water assists some gill ventilation.
4. Lungs (Figures 11.21-11.23)
a. Despite the high oxygen levels in air, gills do not function in air because they dry out.
b. Some invertebrates including snails, scorpions, some spiders, etc. have inefficient “lungs.”
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
c.
d.
Terrestrial vertebrates generally have lungs that can be ventilated by muscle movements.
The most rudimentary lungs exist in lungfishes.
1) The lungfish lung has a rich supply of capillaries on unfurrowed walls.
2) A tube connects it to the pharynx.
3) It uses a primitive ventilating system to move air in and out of the lung.
e. Amphibian lungs vary from smooth-walled, bag-like salamander lungs to divided lungs of frogs.
f. Reptiles lungs have greater surface area because they are subdivided further into air sacs.
g. The mammalian lung has millions of small sacs, called alveoli.
h. Human lungs have 1000 kilometers of capillaries and 50-90 square meters of surface area.
i. However, in contrast to flow over a gill, the air does not continuously enter a lung.
j. About one-sixth the air in human lungs is replenished each inspiration.
k. Bird Lungs
1) Bird lungs have an extensive system of air sacs as reservoirs during ventilation.
2) On inspiration, 75% of air bypasses the lungs to enter the air sacs.
3) At expiration, the fresh air flows through lung passages providing continuous gas exchange.
l. Amphibians force air into their lungs by positive pressure breathing; this requires external nares
and the ability to seal nares and mouth.
m. Most reptiles, birds and mammals ventilate lungs by negative pressure, sucking air in by
expanding the thoracic cavity.
D. Structure and Function of the Mammalian Respiratory System
1. Structure
a. Air enters the mammalian respiratory system through nostrils.
b. It passes through nasal chambers lined with mucus-secreting epithelium.
c. The internal nares are openings leading to the pharynx where the pathway crosses with
digestion.
d. Inhaled air passes out a narrow opening, the glottis, while food crosses to enter the esophagus.
e. The glottis opens into the larynx or voice box and then into the trachea or windpipe.
f. The trachea branches into two bronchi, one to each lung.
g. The bronchus divides and subdivides into small bronchioles that lead to alveoli.
h. Alveolar walls are made of single-layered endothelium.
i. Air passageways are lined with mucus-secreting and ciliated epithelial cells.
j. Partial cartilage rings in the tracheae, bronchi, and bronchioles prevent collapsing.
k. During this passage, inhaled air is filtered free from most dust, warmed, and moistened.
l. The lungs are mostly elastic tissue and a little muscle.
m. A thin layer of visceral pleura encloses the lung; parietal pleura lines the inner wall of the chest.
n. The two layers are lubricated and slide past each other during ventilation.
o. The spine, ribs and breastbone surround the thoracic cavity.
p. The diaphragm forms the floor, and a muscular diaphragm is only found in mammals.
2. Ventilating the Lungs (Figure 11.24)
a. The chest cavity is an airtight chamber.
b. In inspiration, the ribs are pulled upward and the diaphragm flattens; this enlarges the chest.
c. The increase in volume causes air pressure in the lungs to fall below atmospheric pressure.
d. Air rushes in through the air passageways to equalize the pressure.
e. Normal expiration involves relaxation of ribs and diaphragm that return to the normal position.
f. Chest cavity size decreases and air exits.
E. Coordination of Breathing
1. Breathing is normally involuntary and automatic but can come under voluntary control.
2. Neurons in the medulla of the brain regulate normal, quiet breathing.
3. They produce regular spontaneous bursts that stimulate the external intercostal muscles.
4. Respiration must increase dramatically when there is a high requirement for oxygen.
5. However, the body cues on the increasing carbon dioxide level rather than the decrease in oxygen.
6. As carbon dioxide increases, an increase in hydrogen ions making the cerebrospinal fluid acidic.
7. Carbon dioxide combines with water to form carbonic acid that releases hydrogen ions.
F. Gaseous Exchange in Lungs and Body Tissues: Diffusion and Partial Pressure (Figure 11.25)
1. Air is a mixture of 71% nitrogen, 20.9% oxygen, 0.03% carbon dioxide and a few other gases.
2. Gravity attracts the mass of atmosphere to the earth; total air pressure is 760mm Hg.
3. Each component gas contributes to this total; each component gas therefore has a partial pressure.
(Table 11.1)
4. Partial pressure of oxygen is 0.209 x 760 or 159mm Hg.
5. Partial pressure of carbon dioxide is 0.0003 x 760 or 0.23mm Hg in dry air.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
6.
7.
8.
Water vapor likewise exerts a partial pressure.
Air entering the respiratory tract changes in composition; it becomes wet and mixes with residual air.
The partial pressure of oxygen in the lung alveoli is greater (100mm Hg) than in the venous blood of
lung capillaries (40mm Hg), oxygen diffuses into the lung capillaries.
9. The carbon dioxide in the blood of lung capillaries has a higher concentration (46mm Hg) than in the
lung alveoli (40mm Hg) and carbon dioxide diffuses from blood to alveoli.
10. In tissues, respiratory gases continue to move along concentration gradients.
G. Respiratory Gas Transport (Figure 11.26)
1. In some invertebrates, respiratory gases are merely dissolved in body fluids.
2. Only animals with low metabolism can survive on such low levels of oxygen.
3. Only one percent of the human oxygen requirement could be provided by dissolved oxygen.
4. In many invertebrates and all vertebrates, respiratory pigments are used to transport oxygen.
5. In most animals and in all vertebrates, the pigments are packaged in blood cells.
6. Hemoglobin
a. Hemoglobin is the most widespread respiratory pigment among animals.
b. Each molecule is made of 5% heme, an iron-compound and 95% globin, a colorless protein.
c. The heme portion has a great affinity for oxygen; each gram can carry 1.3 ml of oxygen.
d. Heme also holds oxygen in a loose enough chemical state that tissues can take it away.
7. Other Pigments
a. Hemocyanin is a blue, copper-containing protein present in crustaceans and most molluscs.
b. Hemerythrin is a red pigment found in some polychaete worms; it does not have a heme group
and it has lower oxygen-holding properties.
8. Hemoglobin has a 200 times greater affinity for carbon monoxide than for oxygen and can displace
oxygen, resulting in death.
9. Hemoglobin Saturation Curves
a. Also called oxygen dissociation curves, they show the relationship to surrounding oxygen
levels.
b. The lower the surrounding oxygen tension, the more oxygen released.
c. This allows more oxygen to be released to tissues that need it most.
d. Carbon dioxide shifts the hemoglobin saturation curve to the right; this is the Bohr effect.
e. Therefore, as carbon dioxide enters the blood from respiring tissues, it causes hemoglobin to
unload more oxygen.
f. The opposite occurs in the lungs and more oxygen is loaded onto hemoglobin.
10. Carbon Dioxide Transport (Figure 11.27)
a. About 7% of carbon dioxide is carried dissolved in the blood.
b. The remainder diffuses into red blood cells where 70% of it becomes carbonic acid through the
action of the enzyme carbonic anhydrase.
c. Carbonic acid immediately dissociates into hydrogen ions and bicarbonate ions.
d. Several systems buffer the hydrogen ions to prevent blood acidity.
e. About 23% of the carbon dioxide combines reversibly with hemoglobin, not with the heme, but
with the amino acids to form carbaminohemoglobin.
f. The reaction is reversible and the carbon dioxide diffuses into alveoli in the lungs.
Lecture Enrichment
1.
2.
3.
4.
Note that the short four-month lifetime of the red blood cell is directly related to its inability to repair itself since it
has lost nuclear DNA, ribosomes, mitochondria, etc.
Red blood cells become damaged and fragment from wear-and-tear because, unlike other cells, they cannot repair
themselves. Therefore, they are pulled from circulation by macrophages as they pass through the liver and some
components are recycled, a process that can be compared with worn out money being pulled from circulation as it
passes through banks.
In discussion of the heart structures, the terms “right” and “left” are particularly important. This is a point where
you can remind students that directions and positions are named from the perspective of the organism that
possesses the structure, not right and left as an observer would designate viewing the organism or person head-on.
It can be noted that pulmonary circulation is not used for oxygen before birth in placental mammals because
oxygenated blood is received from the umbilical connection to the placenta. Therefore, it is not critical that the
heart have a completely separated septum before birth, and this is indeed the case where the foramen ovale, or
opening across the heart wall, does not close until late in pregnancy. If it fails to close, the baby is a “blue baby”
which reflects the lower level of oxygenated blood; and the inability of this baby to live very long without an
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Copyright © 2005 – The McGraw-Hill Companies srl
5.
6.
7.
8.
operation to close the opening is obvious evidence of our need to completely separate pulmonary and systemic
circulation.
The historical notes of Stephan Hales (blood pressure of a mare) and Marcello Malpighi (capillaries in living frog
lung) are just a few of many critical breakthrough experiments that relied on experiments with living animals.
Such examples may elicit revulsion from students who have been sheltered from meat processing farm
experiences and surgical and emergency room procedures. While discussion of these historical discoveries may
provide an intellectual perspective on reality-based laboratory work, only actual labwork by students will give
them a fuller understanding of the concepts and the need for such research practices.
An instructor can illustrate a simple diagnostic test of edema. Pressing on the surface of soft tissue in the hand,
arm, ankle, etc. with a thumb will leave a white thumbprint for about 3-5 seconds as blood has been pressed out of
the capillaries in the surface tissue and takes this much time to return. However, if there is fluid in these tissues,
the thumbprint depression will remain long after the white blanched area has returned to pink. Note that you are
using a teaching technique and not practicing medicine.
Some zoology teachers are accomplished at simulating positive pressure breathing of a frog by taking a mouthful
of air, sealing the nose and lips, and pressing the bloated cheeks so the air appears to be forced into the lungs.
Gases dissolved in fluids are not beyond student experience; the difference between a fizzy soda and a flat soda is
dissolved carbon dioxide, and the bubbles of gas can be seen sparkling off the top of a newly poured drink.
Commentary/Lesson Plan
Background: To the extent students have participated in blood drives and given blood, they will have experiences
with some blood properties, the speed of replenishment, the viscosity, and the equipment involved, including the long
tube that is crimped to provided samples for cross-matching. Students who have run on a cold, dry winter day have
experienced a mild pleurisy where the pleural membranes stick together from dryness.
Misconceptions: Sadly, blood has moved from a public image of “river of life” to potential “river of death.” With the
advent of AIDS and greater awareness of hepatitis (a far greater infection risk than AIDS), the fear is overblown and a
rational discussion of its biology may help restore some objectivity. A few people still believe that some aspects of
heredity including temperament “run in the blood line”; this is ironic since red blood cells are the only common body
cells that lack hereditary material and this old concept could not be farther from the truth. Some students have the
wrong perception that humans have the “best” or “most advanced” of all systems and yet the bird has a far more
efficient lung. Such a high efficiency lung is not needed by a lower metabolism human, just as an alveolar lung is not
useful to an ectothermic frog.
Schedule:
HOUR 1 11.1. Internal Fluid Environment
A. Fluids
B. Composition of the Body Fluids
11.2. Composition of the Blood
A. Elements
B. Hemostasis; Prevention of Blood
Loss
11.3. Circulation
A. General Design
B. Open and Closed Circulations
C. Plan of Vertebrate Circulatory
Systems
HOUR 2
D. Arteries
E. Capillaries
F. Veins
G. Lymphatic System
11.4. Respiration
A. Processes
B. Problems of Aquatic and Aerial
Breathing
C. Respiratory Organs
D. Structure and Function of the
Mammalian Respiratory System
E. Coordination of Breathing
F. Gaseous Exchange in Lungs and Body
Tissues: Diffusion and Partial Pressure
G. Respiratory Gas Transport
ADVANCED CLASS QUESTIONS:
1. What factors limit the size and life span of a red blood cell? How could an experiment be constructed that
demonstrated the inability of a red blood cell to repair itself?
2. If there is no DNA in red blood cells, then how do forensic scientists identify the blood from a crime scene and
establish the DNA match with the accused? [This involves students comprehending that RBC proteins are placed
on the membrane when the cells are formed and that there are nuclei present in the WBCs of a blood sample.]
3. Why is an opening across the heart septum, called the foramen ovale and a normal fetal condition, not a problem
before birth?
4. Arteries and veins are named by their relationship in blood flow from or to the heart. Generally, arteries carry
oxygenated blood and veins carry deoxygenated blood, but the pulmonary arteries and veins are the reverse of
Fondamenti di zoologia
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Copyright © 2005 – The McGraw-Hill Companies srl
5.
6.
7.
this. What other human circulatory circuit has such a reversal? [Answer: the umbilical cord leading to the
placenta, before birth.]
Why would a heavier person be more likely to have higher blood pressure?
Why are the substantial plasma proteins found in blood not used by cells as a source of metabolic energy?
Some terrestrial mammals ignore declining oxygen levels, and cue on to the reciprocal increase in carbon dioxide
to regulate breathing. However, some diving marine mammals pace breathing on oxygen sensors. Why would
this have evolved?
Twelfth Edition Changes:
1.
2.
3.
4.
5.
6.
Changes in this chapter are relatively minor:
There are approximately 54 million (not billion) blood cells per millileter of blood in adult men and 48
million (not billion) blood cells per milliliter of blood in women.
Scientists now think that inflammation precedes the accumulation of fat in the arteries.
Arteries father away from the heart possess more smooth muscle and less elastic fibers than those nearer the
heart.
About 25 percent of incoming air passes over the lung parabronchi (one-cell thick air capillaries) where gas
exchange takes place.
Peripheral chemoreceptors, located closet to the heart and in the neck region, monitor changes in blood levels
of carbon dioxide and hydrogen ions and send stimulating signals to the medulla respiratory centers if these
levels rise.
Bicarbonate ions are transported out of the red blood cells in exchange for chloride ions (the chloide shift).
Source Materials
[Bold = recommended; vendor abbreviations are provided in Appendix 1]
Asthma (FH), 19-min. video
Blood (FH) (IM), 22-min. video
Blood: Composition and Functions (IM), 15-min. video
Blood Is Life (FH), 45-min. video
Blood and Immunity (CAM) (Cyber) (Q), Mac, MS-DOS CD
Blood Is Life (FH), 45-min. video
Blood: The Microscopic Miracle (EBE), 22-min. video
Blood: River of Life, Mirror of Health (HRM), video
Body Atlas: The Human Pump (AVP) (JLM), 30-min. video
Body Atlas: Breath of Life (AVP) (JLM), 30-min. video
Body Language: Respiratory System (PLP), Apple, MS-DOS, Mac
Breath of Life (FH), 26-min. video
Breaths of Life: Respiratory Challenges of Animals (Biology: Form and Function) (CPB) (IM), 24-min. video
The Cardiac Cycle (JB) (Q), Mac, Win CD
Cardiac Muscle Mechanics (Q) (SciT) (TS), MS-DOS
Cardiovascular Disease (series) (Ch-F), 45-min. video
Cardiovascular Fitness Lab (CBSC), Apple, MS-DOS
Cardiovascular Function (PLP), MS-DOS
Cardiovascular Programs (C-E-G) (JB), MS-DOS
Cardiovascular Physiology Part I: Pressure/Flow Relations (C-BE), MS-DOS
Cardiovascular Physiology Part II: Reflex (C-BE), MS-DOS
Cardiovascular Simulation Program: Computer Rabbit (INT), Mac
Cardiovascular System (CBSC) (PLP), Apple, MS-DOS, Mac
Cardiovascular System (CAM), Mac, Win CD
Cardiovascular System by Logal (WARDS), Mac, Win CD
Cellular Respiration (ei), slides
Comprehensive Review in Biology: Circulation and Respiration (Q), Mac, Win
CIRCSIM: A Teaching Exercise on Blood Pressure Regulation (C-BE), MS-DOS
CIRCSYST 2.0 (C-E-G) (JB), MS-DOS
Circulation (ei), video or filmstrip
Circulation (IM), 29-min. video
Circulation of the Blood (AIMS), Mac, Win CD, 24-min. video, laserdisc
Circulatory and Respiratory Systems (IM) (NGS), 17-min. video
Circulatory System (PHO), 16-min. video
298
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Circulatory System and Its Functions (ei), slides
Circulatory System: Breath of Life (FH), 26-min. video
Circulatory System: Hot and Cold (FH), 26-min. video
The Circulatory System: Life under Pressure (FH), 26-min. video
Circulatory System: Two Hearts That Beat as One (FH), 26-min. video
Comprehensive Review in Biology: Circulation and Respiration (Q), Mac, Win
Coronary Heart Disease: Clinical Aspects (PYR), 17-min. video
Cycles of Life: Exploring Biology–Circulation: A River of Life (A-CPB), 30-min. video
Cycles of Life: Exploring Biology–Respiration (A-CPB), 30-min. video
Diffusion (IM), 29-min. video
EKGTUTOR (C-E-G), MS-DOS
Electrophysiology of the Heart (Q), Mac, Win CD
FICKSYST (C-E-G) (JB), MS-DOS
Frog Heart (INT) (JB), Mac
GASP: A Teaching Exercise on Chemical Control of Ventilation (C-BE), MS-DOS
Growing Old in a New Age–How the Body Ages (A-CPB), 1-hr. video
Growing Old in a New Age–Illness and Disability (A-CPB), 1-hr. video
The Heart (IM), 29-min. video
Heart (NEB), 14-min. video
Heart Abnormalities and EKGs: A Simulation (PLP), Apple
Heart Attack: The Unrelenting Killer (MF), 28-min. video
Heart Dissection and Anatomy (IM), 14-min. video
Heart: the Engine of Life (Q), MS-DOS CD
Hearts and Circulatory Systems (PHO), 14-min. video
How Blood Clots (PHO), 13-min. video
Heart: the Engine of Life (Q), MS-DOS CD
Human Body Series: Circulatory System (PHO), 16-min. video
Human Body Series: Respiratory System (PHO), 13-min. video
Human Circulatory System (EME), Apple II, Mac, MS-DOS
Human Electrocardiogram (INT) (SciT), Mac
Human Lung (INT), Mac
Human Physiology: Circulation (CBSC) (PH), 9-min. filmstrip
Human Physiology: Respiration (CBSC), filmstrip
Hypertension: Your Blood Pressure Is Showing (MF), 28-min. video
Incredible Voyage (CRM), 26-min. video
The Interactive Heart (Q), MS-DOS CD
Introduction to General Biology: The Human Body I (Q), Mac, DOS
Leukemia (FH), 22-min. video
Living Body: Breath of Life (FH), video
Lungs (Revised) (AIMS), Mac, Win CD, 10-min. video, laserdisc
Lymphatic System, The (IFB), 15-min. video
MacFrog Academic (INT), Mac
MacPig (INT), Mac
The Mammalian Heart (AIMS), Mac, Win CD, 15-min. video, laserdisc
Nerves and Heartbeat Rate (BSCS Classic Inquiry) (MDA), videodisc
The Nose: Structure and Function (EBE), 11-min. video
NOVA: Cut to the Heart (NEB) (WGBH), 60-min. video
NOVA: Dying to Breathe (NEB), 60-min. video
NOVA: Heart-to-Heart: The Truth About Heart Disease (NEB), 60-min. video
Our Nation's Blood Supply: The Next Threshold for Safe Blood (FH), 22-min. video
Physiology of Exercise (CBSC), 26-min. filmstrip
Respiration (IM), 29-min. video
Respiration in Man (EBE), 26-min. video
Respiration and Waste (WARDS), 8-min. video
Respiratory Programs (C-E-G) (JB), MS-DOS
Respiratory System (PLP), MS-DOS
Respiratory System (CAM), Mac, Win CD
The Respiratory System [Simulations in Physiology] (NRCLSE), MS-DOS, Apple and Mac
Respiratory System and Its Function (ei), slides or filmstrip
RESPSYST 2.0 (C-E-G), MS-DOS
299
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
RESPWIN 3.0 (JB), Win
SimHeart (THIEME), Mac, Win CD
SimVessel (THIEME), Mac, Win CD
Tuberculosis (FH), 50-min. video
Two Hearts that Beat as One (FH), 28-min. video
VENTROL (C-E-G) (JB), MS-DOS
William Harvey (IM) (UC), 19-min. video
William Harvey and the Circulation of Blood (FH), 29-min. video
The World of Chemistry–The Precious Envelope (A-CPB), 30-min. video (atmosphere)
Young Hearts (HE), 27-min. video
300
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Copyright © 2005 – The McGraw-Hill Companies srl
CHAPTER 12
DIGESTION AND NUTRITION
CHAPTER OUTLINE
12.1.
12.2.
Trophic Levels and Routing
A. Classification
1. Sunlight provides the ultimate source of energy for life.
2. Green plants are autotrophic organisms; most are chlorophyll-bearing phototrophs.
3. Some gain energy from inorganic chemical reactions and are chemotrophs.
4. Almost all animals are heterotrophic organisms that depend on compounds already synthesized.
5. Herbivorous animals mainly feed on plant life.
6. Carnivorous animals feed on herbivores and other carnivores.
7. Omnivorous animals feed on both plants and animals.
8. Saprophagous animals feed on decaying organic matter.
B. Routing
1. Ingestion of foods and their reduction by digestion only begins the steps in nutrition.
2. Foods reduced by digestion are absorbed into the circulatory system.
3. Foods are transported to the tissues of the body.
4. They are assimilated into the structure of cells.
5. Oxygen is also transported to tissues where food products are oxidized to yield energy and heat.
6. Food not immediately used is stored for future use.
7. Wastes produced by oxidation must be excreted.
8. Food products unsuitable for digestion are egested in the form of feces.
Feeding Mechanisms (Figures 12.1, 12.2)
A. Feeding on Particulate Matter
1. Ocean drifting microscopic particles consist of plankton and organic debris.
2. The richest zones occur in estuaries and upwellings and feed many larger animals.
3. Suspension Feeders
a. Suspension feeders use ciliated surfaces to draw drifting food particles into their mouths.
b. Many trap particulate food on mucous sheets that convey food to the digestive tract.
c. Others use sweeping movements to convey particles to their mouth.
e. Suspension or filter-feeding has evolved many times among crustaceans, sharks, whales, etc.
4. Deposit Feeding
a. This variation of particulate feeding extracts organic material or detritus from substrate.
b. Some annelids and hemichordates pass the substrate through their bodies and remove nutrients.
c. Scaphopods and some bivalve molluscs use appendages to gather in organic deposits.
B. Feeding on Food Masses (Figures 12.3-12.6)
1. Some animals that eat solid food are heavily adapted for this task.
2. Predators locate, capture, hold and swallow prey.
3. Some carnivores seize food and swallow it intact; some may employ toxins.
4. Although invertebrates lack true teeth, some have beaks or tooth-like structures to bite and hold.
5. The polychaete Nereis seizes food with jaws on a muscular pharynx.
6. Fish, amphibians and reptiles use teeth to grip prey until it is swallowed.
7. Many invertebrates can reduce food by shredding devices.
8. True mastication or chewing is only found among mammals where there are four types of teeth.
a. Incisors bite, cut and strip.
b. Canines seize, pierce and tear.
c. Premolars and molars are for grinding and crushing.
9. Variations in teeth reveal the specialized food habits of animals.
a. Herbivores have suppressed canines and well-developed molars.
b. Rodents have well-developed and self-sharpening incisors that must be constantly worn away.
c. An elephant’s tusk is a modified upper incisor used for defense, attack and rooting.
10. Some invertebrates have specialized scraping mouthparts, such as the radula of the snail.
11. Horses are herbivorous mammals that have corrugated molars for grinding plant tissue.
C. Feeding on Fluids
1. Fluid feeding is especially characteristic of parasites.
2. Some internal parasites simply absorb the nutrients around them.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
3.
4.
12.3.
12.4.
Some bite or rasp the tissues of the host to suck the blood or feed on intestinal contents.
Leeches, lampreys, mosquitoes, sucking lice, bedbugs, ticks and mites and fleas are a few of the
organisms that feed on blood or other body fluids and some may vector disease agents.
5. Parasites that feed on blood, such as the mosquito, use an anticoagulant to keep blood from clotting.
Digestion (Figure 12.7)
A. Overview
1. Digestion mechanically and chemically breaks food into small units for absorption.
2. Food solids contain carbohydrates, proteins and fats that must be reduced to simpler molecules.
3. An animal must then reassemble the digested and absorbed units into the animal’s own compounds.
4. Digestion in sponges and protozoa is entirely intracellular; food particles are phagocytized.
5. Intracellular digestion is limited in the size of food particle that can be utilized.
6. The invention of the alimentary system allowed extracellular digestion to take place.
7. This allowed cells lining the lumen of the alimentary canal to specialize for digestion or absorption.
8. Development of mouth-to-anus flow-through systems allowed regional specialization of digestion.
B. Action of Digestive Enzymes (Figure 12.8)
1. Mechanical processes of cutting and grinding are important but limited to reducing size of foods.
2. Reduction of molecules to absorbable size relies on chemical breakdown by enzymes.
3. Digestive enzymes are hydrolytic enzymes or hydrolases; molecules are split by adding water.
4. Proteins must be split into hundreds or thousands of small amino acid molecules.
5. Carbohydrates must be reduced to simple sugars.
6. Fats are reduced to glycerol and fatty acids although some are absorbed without being hydrolyzed.
7. Specific enzymes form an “enzyme chain” so one may complete what another has started.
C. Motility in the Alimentary Canal
1. Food moves through the digestive tract by cilia, specialized musculature or both.
2. Acoelomate and pseudocoelomate animals lack mesodermally derived gut musculature and use cilia.
3. Most molluscs also use cilia; the coelom is weakly developed.
4. In coelomic animals, the gut is lined with circular and longitudinal layers of smooth muscle.
5. Gut movements cause segmentation, alternate constriction of rings of muscle to divide gut contents;
this mixes food but does not move it through the gut.
6. Peristalsis, or waves of contractions, moves food down the gut.
Organization and Regional Function of the Alimentary Canal (Figures 12.9, 12.10)
A. Receiving Region
1. Mouthparts may include mandibles, jaws, teeth, radula or bills.
2. The buccal cavity and pharynx are inner chambers.
3. Most metazoans, other than suspension feeders, have salivary glands to produce lubricating
secretions.
4. Salivary Glands
a. Specialized saliva may contain toxins to quiet struggling prey.
b. Leech saliva contains an anaesthetic and enzymes to prevent blood coagulation and increase
flow.
c. Salivary amylase is found in herbivorous molluscs, insects and primate mammals.
d. Salivary amylase breaks starch into two-glucose fragments of maltose.
5. Tongue
a. Only vertebrates evolved a tongue, usually attached to the floor of the mouth.
b. It assists in food manipulation and swallowing.
6. As food is moved toward the pharynx, the nasal cavity reflexively raises the soft palate.
7. The epiglottis keeps food from entering the trachea.
8. Food in the esophagus is smoothly moved by peristalsis to the stomach.
B. Conduction and Storage Region
1. The esophagus of vertebrates and many invertebrates moves food to the digestive system.
2. In annelids, insects and octopods, the esophagus is expanded into a crop, a food storage area.
3. Among vertebrates, only birds have a crop; it softens grain and allows mild fermentation.
C. Region of Grinding and Early Digestion (Figure 12.11)
1. The stomach is a region for initial digestion and storage of food in vertebrates and some invertebrates.
2. Herbivorous animals often continue the grinding and crushing of plants in the stomach.
3. Swallowed stones and grit assist the muscular gizzard of oligochaete worms and birds.
4. The insect proventriculus has chitinous teeth, and crustaceans have a gastric mill.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
5.
Digestive diverticula are blind tubules or pouches that supplement the stomach and secrete enzymes
and/or absorb nutrients.
6. The Problem with Cellulose
a. The woody cellulose that encloses plant cells is a very abundant molecule.
b. Only the enzyme cellulase can break down the cellulose molecule.
c. No metazoan animal can produce cellulase for direct digestion of cellulose.
d. Many herbivorous animals harbor bacteria and protozoa in their gut that do produce cellulase.
e. These microorganisms ferment cellulose under anaerobic conditions of the gut, producing fatty
acids and sugars.
f. Ruminant mammals harbor these organisms in a multi-chambered stomach.
g. Other animals harbor the microorganisms in the intestine or the cecum.
7. Acidity of the stomach is probably an adaptation for killing prey and halting bacterial activity.
8. A cardiac sphincter opens to allow food to enter from the esophagus; it closes to prevent
regurgitation.
9. In humans, peristaltic waves churn the stomach at about three waves per minute.
10. Food is released into the intestine by the pyloric sphincter.
11. Gastric Glands
a. In humans, tubular glands in the stomach wall secrete about 2 liters of gastric juice a day.
b. Chief cells secrete pepsin, a protease that only acts in an acid medium (pH 1.6 to 2.4).
c. The pepsin breaks down only specific peptide bonds; other proteases will split all peptide bonds.
d. Pepsin is present in the stomachs of nearly all vertebrates.
e. Parietal cells secrete hydrochloric acid.
12. Rennin is a milk-curdling enzyme found in the stomach of ruminants and other mammals.
13. Secretion of gastric juices increases at the sight of food, food in the stomach or during anxiety.
14. Classic experiments were made in 1825-1833 by Army surgeon William Beaumont who observed
stomach action through a permanent gunshot wound in a patient.
15. The use of a permanent opening or fistula is common in animal digestive research.
D. Region of Terminal Digestion and Absorption: The Intestine (Figures 12.12, 12.13)
1. Absorptive Structures
a. In invertebrates with digestive diverticula, the intestine may serve only to carry wastes away.
b. In invertebrates with simple stomachs and in vertebrates, intestines digest and absorb nutrients.
c. One method to increase digestive surface is to increase the length of the intestine.
d. A coiled intestine is rare in invertebrates but may be eight times body length in some mammals.
e. Invertebrates may use infolding to increase surface area as in the typhlosole in oligochaetes.
f. Lampreys and sharks have longitudinal or spiral folds in their intestines.
g. Villi are minute finger-like projections that increase the surface area of some vertebrate
intestines.
h. Each cell likewise has short microvilli that, along with villi, increase surface area a million
times.
2. Digestion in the Vertebrate Small Intestine (Figure 12.14)
a. The pyloric sphincter releases acidic food into the small intestine.
b. The initial segment is the duodenum where pancreatic juice and bile are also added.
c. Both have high bicarbonate content, which neutralizes the stomach acid.
d. The liquified food mass is now liquid chyme; its pH rises from 1.5 to 7.
e. All intestinal enzymes function near this neutral pH.
f. Cells of the intestinal mucosa are constantly being shed in large numbers.
g. Pancreatic Enzymes (Table 12.1)
1) Trypsin and chymotrypsin are proteases that split apart peptide bonds in protein molecules.
2) Carboxypeptidase removes the amino acids from carboxyl ends of polypeptides.
3) Pancreatic lipase hydrolyzes fats into fatty acids and glycerol.
4) Pancreatic amylase is a starch-splitting enzyme identical to salivary amylase.
5) Nucleases degrade RNA and DNA to nucleotides.
h. Membrane Enzymes
1) Cell lining the intestine have digestive enzymes embedded in their surface membrane.
2) Aminopeptidase splits terminal amino acids from the amino end of short peptides.
3) Disaccharidases split 12-carbon sugar molecules into 6-carbon units; this includes maltase,
sucrase and lactase.
4) Alkaline phosphatase is an enzyme that attacks several phosphate compounds.
Fondamenti di zoologia
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Copyright © 2005 – The McGraw-Hill Companies srl
Bile
1) The liver secretes bile into the bile duct that drains into the duodenum.
2) Between meals, the bile collects in the gall bladder that responds to fat in the duodenum.
3) Bile contains water, bile salts, and pigments but no enzymes.
4) Bile salts reduce fat droplets to smaller size to allow increased enzyme action.
5) Bile contains pigments from hemoglobin breakdown and gives feces its dark color.
j. Liver Functions
1) The liver is a storehouse for glycogen.
2) It also produces proteins, detoxifies protein wastes, and destroys worn-out red blood cells.
3) The liver also is the center for metabolism of fat, amino acids and carbohydrates.
3. Absorption
a. Little food is absorbed in the stomach; digestion is not complete and absorptive surface is
limited.
b. Most digested food is absorbed by the villi of the small intestine.
c. Sugars are absorbed as monosaccharides; the intestine is impermeable to polysaccharides.
d. Proteins are absorbed as amino acids or small protein or peptide fragments.
e. Both active and passive processes transfer sugars and amino acids across intestinal epithelium.
f. Passive transfer would only occur after meals when intestinal concentrations were highest.
g. Glucose, galactose and most amino acids are transported by specific transport molecules.
h. Fat droplets are emulsified by bile salts and digested by pancreatic lipase.
i. Micelles of resulting monoglycerides and fatty acids are absorbed across villi by simple
diffusion.
j. The endoplasmic reticulum of absorptive cells resynthesizes them into triglycerides and passes
them into lacteals that transfer them to the lymph system and blood.
E. Region of Water Absorption and Concentration of Solids
1. The large intestine consolidates the undigested material as semisolid feces.
2. Reabsorption of water is the main function and is critical in desert species.
3. Some animals have specialized rectal glands to absorb water and ions, leaving nearly dry fecal pellets.
4. In reptiles and birds, most of the water is reabsorbed in the cloaca leaving a white paste-like feces.
5. In adult humans, about one-third of the dry weight of feces is bacteria.
6. Bacteria play an important role in degrading organic wastes and providing some vitamins.
Regulation of Food Intake
A. Intake Factors
1. Most animals unconsciously adjust intake of food to balance energy expenditure.
2. A hunger center in the hypothalamus regulates the intake of food.
3. A drop in blood glucose levels stimulates a craving for food.
4. In humans, obesity appears to be a genetic predisposition to gain weight on a high-fat diet and a
reduced ability to burn excess calories by “nonshivering thermogenesis.”
5. Brown Fat
a. Placental mammals have a dark adipose tissue called brown fat, specialized for heat generation.
b. Newborn animals have more than adults; it is located in the chest, upper back and near kidneys.
c. Their abundant mitochondria contain a membrane protein called thermogenin.
d. Thermogenin acts to uncouple production of ATP during oxidative phosphorylation.
e. People of normal weight dissipate excess energy as heat; obese people do not.
f. Brown fat is especially well developed in hibernating species of bats and rodents.
6. The Hypothalamus and the Set Point
a. Fat stores are supervised by the hypothalamus, which has a set point.
b. A high setting can be somewhat lowered by exercise, but the body varies little from the set point.
c. A hormone produced by fat cells and called leptin was discovered in 1995.
d. If fat levels are high, leptin is released and diminishes appetite and increases thermogenesis.
7. White fat tissue comprises the bulk of body fat and is derived from surplus carbohydrates and fats.
B. Regulation of Digestion (Figure 12.15)
1. The gastrointestinal (GI) tract is the body’s most diffuse endocrine tissue.
2. Because of their diffuse origins, the GI hormones have been difficult to isolate and study.
3. Gastrin
a. Gastrin is a small polypeptide hormone produced by endocrine cells in the pyloric stomach.
b. It is secreted on stimulation by parasympathetic nerve endings or when protein enters the
stomach.
i.
12.5.
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Copyright © 2005 – The McGraw-Hill Companies srl
12.6.
c. Its main action is to stimulate hydrochloric acid secretion and increase gastric motility.
d. Gastrin is unusual in that the stomach produces it, and the stomach is also the target tissue.
4. Cholecystokinin (CCK)
a. CCK is secreted by endocrine cells in the walls of the upper small intestine in response to fatty
acids and amino acids in the duodenum.
b. It stimulates gallbladder contraction and increases flow of bile salts into the intestine.
c. CCK stimulates an enzyme-rich secretion from the pancreas.
d. It also acts on the brain to contribute a feeling of satiety, especially after a meal rich in fats.
5. Secretin
a. Secretin was the first hormone to be discovered; it is produced by endocrine cells in the duodenal
wall.
b. It is secreted in response to food and strong acid in the stomach and intestine.
c. It mainly stimulates the release of an alkaline pancreatic fluid that neutralizes stomach acid.
d. It also aids fat digestion by inhibiting gastric motility and increasing bile secretion from the liver.
6. Other GI hormones are being isolated and some appear to play neurotransmitter roles in the brain.
Nutritional Requirements
A. Food Categories and Vitamins (Figures 12.16-12.18)
1. Carbohydrates and fats are required as fuels for energy and for synthesis of various substances.
2. The amino acid units of proteins are needed for synthesis of proteins and other nitrogen compounds.
3. Water is a critical solvent for body chemistry.
4. Inorganic salts are required for anions and cations of body fluids and to form structural components.
5. Vitamins are accessory factors from food that are often built into the structure of many enzymes.
6. Vitamins
a. A vitamin is a simple compound that is not a carbohydrate, fat, protein or mineral.
b. Vitamins are needed in very small amounts for some specific cellular function.
c. Vitamins are not themselves sources of energy, but may be associated with metabolic enzymes.
d. Animals have lost ability to synthesis these needed chemicals and must secure them from food.
e. Vitamins are classified as either fat-soluble or water-soluble.
f. Water-soluble vitamins include the B complex and vitamin C. (Table 12.1)
g. Almost all animals need B vitamins and they are considered “universal” vitamins.
h. Dietary need for vitamin C and fat-soluble vitamins A, D, E and K is restricted to vertebrates.
i. A rabbit does not require vitamin C, but guinea pigs and humans do.
j. Some songbirds require vitamin A and others do not.
B. Essential Nutrients and Malnutrition
1. It has long been recognized that lack of certain nutrients resulted in dietary deficiency diseases.
2. Essential nutrients are needed for normal growth and maintenance and must be supplied in a diet.
3. Nearly 30 organic chemicals (vitamins and amino acids) and 21 elements are essential for humans.
4. This is a short list compared to the thousands of organic compounds in the body.
5. Most compounds can be synthesized in the animal cell.
6. Lipids are needed to provide energy; three fatty acids are needed because we cannot synthesize them.
7. A human diet that is high in saturated lipids may be associated with atherosclerosis.
8. Of the 20 amino acids commonly found in proteins, eight are essential to humans.
9. All eight essential amino acids must be present for protein synthesis.
10. Amino acids cannot be stored and they are soon broken down for energy.
11. Use of several plants in a diet will probably provide the full spectrum of needed amino acids.
12. Animal proteins are a rich source of amino acids.
13. Undernourishment includes marasmus in infants on a low-calorie-low-protein diet, and kwashiorkor
that occurs in infants also lacking an adequate diet.
14. Malnutrition in late stages of pregnancy can lead to a child with uncorrectable brain damage.
15. World population growth is a major force driving the global environmental crisis.
Lecture Enrichment
1.
While a cannibalistic carnivore must reduce food molecules to basic units (e.g., amino acids, fatty acids, etc.) just
as a herbivore does, the assortment of molecules is a closer match to what it needs. Meat, as muscle tissue, can be
more fully utilized by an animal than plant tissue that contains much cellulose and other molecules. Thus, in
general, herbivores must consume much more tissue than carnivores consume, and likewise defecate more.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
2.
3.
4.
5.
The value of saliva and mucin in swallowing can be imagined by thinking about trying to swallow a spoonful of
dry cracker crumbs or blotted cole slaw with no saliva present; it cannot be done without time for more saliva to be
secreted to stick it all together. This mental illustration usually makes sense to most students.
Students can also try to mentally visualize swallowing without using the tongue. They will actually go through the
oral motions in “thinking this out.” If the tongue has to be surgically removed, or as was the case in early history
as a punishment for treason, etc., a person must resort to throwing the head backwards to swallow.
All body tubes are collapsed unless something is in them, with the exception of the trachea, etc. where rings of
cartilage hold them open. Peristalsis is the “milking” of a bolus of food through an otherwise collapsed tube.
The complexity of the liver, both in structure and function, is reflected in the fact that it was one of the last organs
to be successfully transplanted. There is no “liver machine” parallel to a dialysis unit or “kidney machine.”
Commentary/Lesson Plan
Background: Students who have cared for pet or farm animals may have an awareness of animal’s varying nutritional
requirements; however, cat and dog food and some farm feeds can be fairly artificial and distant from their natural food.
Misconceptions: The extent to which humans modify food collection and preparation, masks our underlying biological
adaptations to hunting, gathering and scavenging that molded our digestive biology. Therefore, many students will not
recognize our physical and chemical adaptation to an omnivorous diet and may hold beliefs in vegetarianism,
herbalism, etc. that do not match our biological heritage. There are a wide array of erroneous beliefs about cholesterol,
fat, sugar, vitamins, calories, obesity, etc. due to commercial and cultural values and modern myths.
Schedule:
HOUR 1 12.1. Trophic Levels and Routing
HOUR 2
C. Region of Grinding and Early
A. Classification
Digestion
B. Routing
D. Region of Terminal Digestion and
12.2. Feeding Mechanisms
Absorption: The Intestine
A. Feeding on Particulate Matter
E. Region of Water Absorption and
B. Feeding on Food Masses
Concentration of Solids
C. Feeding on Fluids
12.5. Regulation of Food Intake
12.3. Digestion
A. Intake Factors
A. Overview
B. Regulation of Digestion
B. Action of Digestive Enzymes
12.6. Nutritional Requirements
C. Motility in the Alimentary Canal
A. Food Categories and Vitamins
12.4. Organization and Regional Function of the
B. Essential Nutrients and Malnutrition
Alimentary Canal
A. Receiving Region
B. Conduction and Storage Region
ADVANCED CLASS QUESTIONS:
1. Why do the demands of feeding have such a profound effect on the morphology and behavior of animals compared
to the requirement for reproduction?
2. Are the stomach contents of an animal actually “inside” the animal proper, in the sense that blood or lymph is “in”
the animal? If a baby swallows a dime, is the dime “inside” the baby?
3. Why are stomach contents but not intestinal contents regurgitated?
4. Owls regurgitate the fur, bones, and feathers of prey items as “owl pellets” commonly found on the ground around
their roosts. Would the owl pellet be laden with bacteria similar to feces? Why?
5. Would the crop of an earthworm and a bird be considered homologous structures?
6. Would the gizzard of an earthworm and a bird be considered homologous structures?
7. What evolutionary reasons can you suggest for brown fat being especially well developed in hibernating species of
bats and rodents?
8. A tobacco hornworm caterpillar can eat tobacco but dies if fed milkweed. A monarch butterfly caterpillar eats
milkweed but dies if fed tobacco. Both insects are in the order Lepidoptera and both plants are dicotyledons. What
is the difference in these two insects from the digestive-system-enzyme perspective? Why can’t all herbivorous
insects eat all green plants, and of what importance is this to farmers and gardeners?
Twelfth Edition Changes: There are no major changes in this chapter.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
1.
2.
3.
4.
Tongues are also used as chemosensors and possess taste buds that are used to determine palatability of foods.
The increase in fast food meals, larger portion sizes, and more sedentary life style is associated with the
prevalence of obesity in developed countries.
The majority of obese humans do not respond to infusions of leptin.
Current evidence suggests that inflammation of artery wall precedes deposition of fat. Elevated cholesterol
levels can fuel such inflammation.
Source Materials
[Bold = recommended; vendor abbreviations are provided in Appendix 1]
Animal Nutrition (IM), 29-min. video
Biology–Digestion and Fluid Balance (A-CPB), 30-min. video
Biology–Endocrine Control: Systems in Balance (A-CPB), 30-min. video
Body Atlas: The Food Machine (AVP) (JLM), 30-min. video
Body Language: Digestive System (PLP), Apple, MS-DOS or Mac
Breakdown (FH), 28-min. video
Bulimia (CRM), 12-min. video
The Chemistry of Digestion (PHO), 15-min. video
Comprehensive Review in Biology: Digestion and Excretion (Q), Mac, Win
Cycles of Life: Exploring Biology–Digestion and Fluid Balance (A-CPB), 30-min. video
Diet: Health and Disease (HRM)
Dieting (series) (Ch-F), 67-min. video
Dieting: The Danger Point (CRM), 20-min. video
Digestion (IM), 29-min. video
Digestion: Breakdown (FH), 26-min. video
Digestion: Eating to Live (FH), 26-min. video
Digestion and Fluid Balance (IM), 30-min. video
Digestion: A Tough Dirty Job, it Takes a Lot of Guts (BSA) 50-min. video
Digestive System (EBE) (IM) (NGS), 18-min. video
Digestive System and Its Function (ei), slides
Eating to Live (FH), 26-min. video
Exercise Physiology (PLP), MS-DOS
Food/Analyst Plus: The Complete Nutritional Analysis Software (CAM), Mac, Win CD
The Food Machine (IM) 25-min. video
Growing Old in a New Age–Illness and Disability (A-CPB), 1-hr. video
Homeostasis (HRM), filmstrip
Human Body: Chemistry of Digestion (PHO), 15-min. video
Human Body: Digestive System (PHO), 16-min. video
Human Body: Nutrition and Metabolism (PHO), 14-min. video
Human Body Series: Digestive System (PHO), 16-min. video
The Human Digestive System (AIMS) (WARDS), Mac, Win CD, 18-min. video, laserdisc
Incredible Voyage (CRM), 26-min. video
Introduction to General Biology: The Human Body I (Q), Mac, DOS
Liver (IFB), 15-min. video
Living Body: The Lower Digestive Tract: Breakdown (FH), 26-min. video
Living Body: The Upper Digestive Tract: Eating to Live (FH), 26-min. video
MacDiet (Fish), Mac
MacDiet Academic Version 4.2 (INT), Mac
MacDiet (INT), Mac CD
Metabolism: The Fire of Life (HRM), video
New Formulae for Food—Artificial Diets for Animals (Biology: Form and Function) (CPB), 24-min. video
NOVA: Fat in a Thin World (WGBH), 55-min. video
Nutrition—A Balanced Diet (EME), Apple II
Our Living World: Parasites (AIMS), Mac, Win CD, 22-min. video
Peptic Ulcer (MF), 12-min. video
Physiology of Exercise (FH), 15-min. video
Physiology: The Gastrointestinal Tract (CBSC), 28-min. filmstrip
Teeth and Their Function (ei), slides
306
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
The Videodisc Encyclopedia of Medical Images (FH), videodisc, MS-DOS
The Waist Land: Eating Disorders (PHO) (MTI), 23-min. video
William Beaumont (UC), 23-min. video
307
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
CHAPTER
13
NERVOUS COORDINATION
CHAPTER OUTLINE
13.1.
Neuron: Functional Unit of the Nervous System
A. Structure (Figures 13.1-13.3)
1. The neuron may assume many shapes depending on function and location.
2. The nucleated cell body has two types of cytoplasmic process.
3. One or often many more dendrites are the nerve cells receptive apparatus.
4. A single axon is often very long and carries impulses away from the cell body.
5. In vertebrates and some complex invertebrates, an insulating sheath of myelin covers the axon.
6. Neurons are afferent or sensory, efferent or motor, and interneurons that connect neurons.
7. Afferent and efferent neurons lie mostly outside the central nervous system (CNS).
8. Interneurons, which in humans make up 99% of all neurons, lie entirely within the CNS.
9. Afferent neurons are connected to receptors that convert stimuli to nerve impulses.
10. Only in the central nervous system are impulses perceived as conscious sensation.
11. When impulses move to efferent neurons, effectors carry them to muscles or glands.
12. A nerve is a bundle of nerve processes, usually axons, wrapped in connective tissue.
13. Cell bodies of the nerve processes are either in the CNS or in ganglia, bundles of nerve cell bodies
outside the CNS.
14. Neuroglial cells surround neurons; in the vertebrate brain, they outnumber neurons by 10 to 1.
15. Schwann cells form the insulating myelin sheath by laying down concentric rings.
16. Oligodendrocytes form the myelin sheath in the CNS.
17. Star-shaped astrocytes serve as nutrient and ion-reservoirs for neurons and as a scaffold during brain
development so neurons can grow to a certain destination.
18. Astrocytes and microglial cells are essential in regenerating tissue after brain injury.
B. Nature of the Nerve Impulse
1. All nerve impulses are the same type of common electro-chemical message of neurons.
2. An impulse is an “all-or-none” effect; either the fiber is conducting an impulse or it is not.
3. The frequency of an impulse is the only variation a nerve fiber can accomplish.
4. Nerve impulses may vary from a few per second to nearly 1000 per second.
5. Resting Membrane Potential (Figure 13.4)
a. Neuron membranes have a permeability that creates ionic imbalances.
b. Interstitial fluid on the outside of neurons has high sodium (Na+) and chloride (Cl-) ion
concentrations and low potassium ion (K+) levels.
c. Inside the neuron membrane, there is a low Na+ and Cl- ion concentration and high K+ levels.
d. At rest, the membrane of a neuron is selectively permeable to K+ but permeability to Na+ is
nearly zero since the Na+ channels are closed.
e. Potassium ions diffuse outward until the positive charge outside repels any more K+ from
exiting.
f. When the electrical gradient balances the concentration gradient that forces the K+ out, the
resting membrane is at equilibrium.
g. Resting potential is usually -70 millivolts with the inside of the membrane negative to the
outside.
6. Action Potential (Figure 13.5)
a. A nerve impulse is a rapidly moving change in electrical membrane potential.
b. This action potential is a very rapid and brief depolarization of the membrane.
c. During the action potential, the membrane potential reverses for an instant with the inside
positive compared to the outside being negative.
d. The nerve impulse is self-propagating; it moves ahead on its own.
e. The reversal of polarity is caused when Na+ channels suddenly open and Na+ floods into the
axon.
f. Only a small portion of Na+ move in but this depolarization creates a minute electrical “hole”
that allows K+ ions to move out, and the next pore over to open.
g. As the action potential passes, the membrane regains its resting properties.
h. Na+ permeability is restored to normal and K+ permeability briefly increases above resting level.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
i.
13.2.
The action potential drops rapidly to the resting membrane level during this repolarization
phase.
7. Sodium Pump
a. Sodium pumps are a complex of protein subunits embedded in the membrane of the axon.
b. Each sodium pump uses energy stored as ATP to transport sodium from the inside to outside.
c. Astrocytes help maintain a correct balance of ions surrounding neurons by sweeping up excess
K+ .
8. High-Speed Conduction (Figure 13.6)
a. Speed varies from 0.1 m/second in sea anemones to 120 m/second in some mammal motor
axons.
b. Speed of conduction is related to diameter of the axon.
c. Small axons conduct slowly because internal resistance to current flow is high.
d. In most invertebrates, fast conduction is important for fast response, and axon diameters are
large.
e. A giant axon of a squid is 1 mm in diameter and carries impulses 10 times faster than most
axons.
f. Vertebrates do not possess giant axons but achieve high speed by using the myelin sheath.
g. Nodes of Ranvier interrupt insulating myelin sheaths where the surface is exposed.
h. Myelin insulation prevents depolarization, which therefore only occurs at the nodes.
i. Saltatory conduction describes this action potential that leaps from node to node.
j. A frog myelinated axon 12 micrometers in diameter conducts nerve impulses as fast as a squid
axon 350 micrometers in diameter.
Synapses: Junction Points between Nerves (Figures 13.7, 13.8)
A. Function
1. An action potential passing down an axon must cross a small gap, the synapse.
2. Electrical Synapses
a. Electrical synapses are uncommon, but have been demonstrated in both invertebrates and
vertebrates.
b. Ionic currents flow directly across a narrow gap junction from one neuron to another.
c. They show no time lag and are important in escape reactions.
d. They also are an important method of communication between cardiac muscle cells of the heart.
3. Chemical Synapses
a. Neurons bringing impulses to the gap are presynaptic neurons.
b. Neurons carrying impulses away are postsynaptic neurons.
c. The synaptic cleft or gap between the neuron tips is about 20 nanometers wide.
d. The presynaptic knobs of axons contain packets of chemicals called neurotransmitters.
e. Many axon terminations may input on the thousands of dendrites of one neuron.
f. The fluid-filled gap between presynaptic and postsynaptic membranes prevents the action
potential from continuing.
g. The presynaptic knobs secrete a neurotransmitter; one of the most common is acetylcholine.
h. The neurotransmitter such as acetylcholine is packaged inside tiny synaptic vesicles.
i. The action potential causes an inflow of Ca+ ions, which induces exocytosis of the synaptic
vesicles.
j. The acetylcholine molecules diffuse across the gap in a fraction of a millisecond.
k. The acetylcholine binds to receptor molecules on ion channels in the postsynaptic membrane.
l. This causes a voltage change in the postsynaptic membrane.
m. If the voltage change is large enough, a new action potential is generated.
n. The size of the voltage change depends on the number of molecules released and channels
opened.
o. The enzyme acetylcholinesterase rapidly converts acetylcholine into acetate and choline; this
prevents the acetylcholine from continuing to stimulate the postsynaptic membrane.
p. Organophosphate insecticides kill by blocking acetylcholinesterase.
q. Choline is eventually reabsorbed into the presynaptic terminal and resynthesized into
acetylcholine.
r. Excitatory synapses occur where neurotransmitters such as acetylcholine, norepinephrine and
glutamate depolarize the postsynaptic membrane.
s. Inhibitory synapses occur where neurotransmitters such as gamma aminobutyric acid
hyperpolarize the postsynaptic membrane and stabilize it against depolarization.
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Copyright © 2005 – The McGraw-Hill Companies srl
t.
13.3.
The net balance of all excitatory and inhibitory inputs determines if a neuron will send an
impulse.
u. The synapse and this summation process are the decision-making equipment of the CNS.
Evolution of the Nervous System
A. Invertebrates: Development of Centralized Nervous Systems (Figures 13.9A-C)
1. Protozoa are unicellular and lack nerves.
2. Nerve Net
a. This is the simplest pattern of nervous system found in sea anemones, jellyfish, hydra and comb
jellies.
b. The nerve net is an extensive network in and under the epidermis.
c. Impulses starting in one part are conducted in all directions; synapses do not direct one-way
impulses.
d. There are no sensory, motor or interneurons.
e. This type of system survives in advanced animals as a nerve plexus that governs intestinal
movement.
3. Bilateral Nervous Systems
a. Flatworms represent the simplest bilateral nervous system.
b. They have two anterior ganglia leading to two main nerve trunks that run posteriorly.
c. Lateral branches form a ladder appearance.
d. This is the simplest system to have a peripheral nervous system extending to all parts of the
body, and a central nervous system concentrating nerve cell bodies.
e. Annelids have advanced to segmented ganglia and distinct afferent and efferent neurons.
f. Segmental ganglia are relay stations for coordinating regional activity.
4. Molluscan Nervous Systems
a. The basic plan centers on three pairs of well-defined ganglia.
b. However, in cephalopods, the ganglia have burgeoned into nervous centers of over 160 million
cells.
5. Arthropod Nervous System
a. The ganglia are larger than those found in annelids.
b. Sense organs are generally better developed.
c. Some social behavior is elaborate, but behavior is reflex-bound and learning is limited.
B. Vertebrates: Fruition of Encephalization
1. Encephalization is the increase and elaboration in size of the brain.
2. The Spinal Cord (Figure 13.10)
a. The brain and spinal cord compose the central nervous system.
b. Both begin as an ectodermal neural groove that folds into a long, hollow neural tube.
c. The cephalic end enlarges into the brain vesicles and the rest becomes spinal cord.
d. Unlike invertebrate nerve cord, segmental nerves of spinal cord are separated into dorsal
sensory roots and ventral motor roots.
e. Both meet to form a mixed spinal nerve.
f. The spinal cord is enclosed in the spinal canal and wrapped in three layers of meninges.
g. In cross section, the spinal cord has an inner gray zone containing the cell bodies of motor
neurons.
h. The outer white zone contains bundles of axons and dendrites linking with other regions and the
brain.
3. Reflex Arc (Figures 13.11A, B)
a. Many neurons work in groups called reflex arcs of at least two neurons and often more.
b. Parts of a Reflex Arc
1) A receptor is a sense organ in the skin, muscle, or other organ.
2) An afferent or sensory neuron carries impulses toward the CNS.
3) The central nervous system makes synaptic connections between sensory and interneurons.
4) The efferent or motor neuron makes a synaptic connection with the interneuron and carries
impulses from the CNS.
5) An effector is a muscle, gland, ciliated cell, electric organ, or pigmented cell that responds.
c. The simplest reflex arc may only have a sensory and motor neuron, as in the “knee-jerk”
example.
d. Usually interneurons are interposed between sensory and motor neurons.
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Copyright © 2005 – The McGraw-Hill Companies srl
e.
4.
Reflex arcs may be complex with many inputs or outputs, and may be modified by motor
neurons.
f. A reflex act is the involuntary response due to a reflex arc.
g. Most are vital processes and are innate, but some are acquired through learning.
Brain (Figures 13.12, 13.13)
a. While the spinal cord has changed little in vertebrate evolution, the brain has changed
dramatically.
b. The primitive linear brain of fishes has become a deeply fissured intricate brain of mammals.
c. The human brain contains 35 billion nerve cells; each cell may receive tens of thousands of
synapses.
d. The ratio of weight of brain to spinal cord provides a scale of intelligence.
1) In fish and amphibians, the brain:spinal cord ratio is about 1:1.
2) In humans, this ratio is 55:1.
e. The brain of early vertebrate fishes has three principal divisions.
1) The prosencephalon, or forebrain, dealt with the sense of smell.
2) The mesencephalon, or midbrain, dealt with vision.
3) The rhombencephalon, or hindbrain, perceived hearing and balance.
f. Hindbrain (Figures 13.14, 13.15)
1) The medulla is the most posterior division of the brain and is a continuation of the spinal
cord.
2) Together with the anterior midbrain, the medulla constitutes the “brain stem” that controls
heartbeat, respiration, vascular tone, gastric secretions and swallowing.
3) The pons contains a thick bundle of fibers that carry impulses to either side of the
cerebellum and connects the medulla and cerebellum to other regions.
g. Cerebellum
1) This lies dorsal to the medulla.
2) The cerebellum controls equilibrium, posture, and movement.
3) It is more developed in agile bony fish and weakly developed in amphibians and reptiles.
4) It is most developed in birds and mammals.
5) It does not initiate movement but is a precision error-control center to program movement.
6) Movements initiated in the motor cortex of the cerebrum are programmed here.
7) Cerebellar coordination can result in simultaneous contraction of hundreds of muscles.
h. Midbrain
1) This consists of a tectum that contains nuclei and serves as centers for visual and auditory
reflexes.
2) In this usage, “nuclei” are small aggregations of nerve cell bodies within the CNS.
3) It mediates the complex behavior of fishes and amphibians using visual, tactile and auditory
input.
4) However, these functions have been assumed by the forebrain in amniotes.
5) In mammals, the midbrain is a relay center for information going to higher brain centers.
i. Forebrain
1) The thalamus and hypothalamus are the most posterior elements of the forebrain.
2) The egg-shaped thalamus analyzes and passes sensory information to higher brain centers.
3) The hypothalamus regulates body temperature, water balance, appetite and thirst.
4) Neurosecretory cells in the hypothalamus produce several neurohormones.
5) The hypothalamus has centers regulating reproductive function, sexual behavior and
emotions.
6) The anterior forebrain is the cerebrum.
7) The cerebrum is divided into the paleocortex and the neocortex.
8) The paleocortex is known as the limbic system and mediates behaviors relating to feeding
and sex, functions that evolutionarily have depended on olfaction.
9) One region, the hippocampus, is involved with spatial learning and memory.
10) Neurons do not divide in adults, but recent research has revealed cell division in the
hippocampus.
11) The neocortex is the cerebral cortex and it has expanded to envelop the forebrain and
midbrain.
12) The cortex contains discrete motor and sensory areas.
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13.4.
13) Large “silent regions” called association areas are concerned with memory, judgment,
reasoning and other integrative functions, but not directly connected to sense organs or
muscles.
j. In mammals and especially humans, separate areas mediate conscious and unconscious
functions.
k. The brain is an endocrine gland that regulates and receives feedback from the endocrine system.
l. The unconscious mind is all of the brain except the cerebral cortex.
m. The conscious mind in the cerebral cortex is the site of higher mental activities.
n. Memory appears to transcend all parts of the brain rather than being a property of any one part.
o. The corpus callosum is a neural connection bridging the right and left hemispheres.
p. In humans, the two hemispheres specialize for different functions.
1) The left hemisphere handles language, mathematical and learning capabilities.
2) The right hemisphere handles spatial, artistic, musical, intuitive and perceptual activities.
q. Birds, likewise, have one side of the brain specialized for song production.
5. Peripheral Nervous System
a. The peripheral nervous system (PNS) includes all nervous tissue outside of the CNS.
b. The sensory of afferent division brings sensory information to the CNS.
c. The motor or efferent division conveys major commands to muscles and glands.
d. The efferent division has two components: somatic nervous system and autonomic nervous
system.
e. Autonomic Nervous System (Figures 13.16, 13.17)
1) This system governs involuntary, internal functions that do not ordinarily affect
consciousness.
2) It controls movements of the alimentary canal and heart, smooth muscle of blood vessels,
urinary bladder, iris of the eye, and secretions of various glands.
3) Autonomic nerves originate in the brain or spinal cord but consist of two motor neurons.
4) They synapse once after leaving the cord and before reaching the effector organ.
5) The synapse outside the spinal cord in ganglia is between preganglionic and postganglionic
fibers.
6) The autonomic system is subdivided into parasympathetic and sympathetic systems.
7) Most organs are innervated by both systems and they both work to control activity.
8) The parasympathetic nervous has motor neurons that emerge from the brain stem or pelvic
region.
9) The sympathetic nervous system nerve cell bodies of preganglionic fibers are located in the
thoracic and upper lumbar areas; their fibers pass out through ventral roots of the spinal
nerves and form a chain along the spine.
10) All preganglionic fibers in both systems release acetylcholine at the pre/postganglionic
synapse.
11) Parasympathetic postganglionic fibers release acetylcholine at their endings, while
sympathetic postganglionic fibers usually release norepinephrine.
12) Generally, the parasympathetic division is active during resting conditions.
13) The sympathetic division is active under conditions of physical activity and stress and
during resting conditions in maintaining normal blood pressure and body temperature.
Sense Organs
A. Stimuli
1. Sense organs are specialized receptors designed to detect environmental status and change.
2. Sense organs are the first level of perception and are channels for bringing information to the brain.
3. A stimulus is some form of energy: electrical, mechanical, chemical or radiant.
4. The sense organ must transform the energy form of the stimulus into nerve impulses.
5. Sense organs are biological transducers and usually respond to only one kind of stimulus.
6. In the 1830s, Johannes Muller detected that animals perceived different sensations only because
impulses originating from one sense organ arrive at a particular sensory area: the “law of specific
nerve energies.”
B. Classification of Receptors
1. Receptors near the external surface are exteroceptors; those in internal organs are interoceptors.
2. Muscles, tendons and joints have proprioceptors sensitive to changes in the tension of muscles and
providing a sense of body position.
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Copyright © 2005 – The McGraw-Hill Companies srl
3.
Receptors can be classified by the form of energy to which they respond: chemical, light, thermal,
etc.
C. Chemoreception (Figures 13.18-13.20)
1. This is the oldest and most universal sense in the animal kingdom.
2. Protozoa use contact chemical receptors to locate food and oxygenated water, and to avoid harmful
substances.
3. Chemotaxis is an orientation behavior toward or away from a chemical source.
4. Most metazoans have specialized and sensitive distance chemical receptors or a “sense of smell.”
5. Olfaction is useful to guide feeding behavior, locate sexual mates, mark territories and elicit alarm.
6. Pheromones
a. Social insects, many mammals and others produce species-specific chemicals to communicate.
b. An animal releases a pheromone to affect the behavior of another member of the same species.
c. Ants have many glands to produce many chemical signals.
d. Releaser pheromones include alarm and trail pheromones.
e. Primer pheromones alter endocrine and reproductive systems of different castes in a colony.
f. Insects therefore bear chemoreceptors on the surface of the body for sensing specific
pheromones.
7. Taste Receptors
a. The sense of taste is more restricted in response and less sensitive than the sense of smell.
b. CNS centers for taste and smell are located in different parts of the brain.
c. In vertebrates, taste receptors are found in the mouth cavity and on the tongue surface.
d. A taste bud is a cluster of several receptor cells surrounded by supporting cells.
e. They are slender sensory cells that project through a small external pore.
f. Molecules being tasted apparently combine with specific receptor sites on microvilli of receptor
cells.
g. The correct chemical will depolarize the specific sensitive cell and generate an action potential.
h. Subjected to wear and tear, taste buds have a short life and are continually replaced.
i. Each of the four tastes detected by humans have a different taste bud: sweet, sour, salty and
bitter.
j. Many potentially dangerous materials are bitter, and this sense is most sensitive.
k. Taste sensations are categorized as sweet, salty, acid, bitter, and possibly unami (“savory”).
l. Contrary to what was originally thought, taste receptors can respond to different types of taste
categories, although they may respond more strongly to one particular type.
m. Taste discrimination depends on assessment by the brain of the relative activity of many
different taste receptors.
8. Sense of Smell
a. Olfaction is most highly developed in mammals, much more so in dogs than in humans.
b. Olfactory endings are located in epithelium in the nasal cavity and covered with a thin film of
mucus.
c. Millions of olfactory neurons lie in the epithelium, each with several hair-like cilia protruding.
d. Odor molecules bind to receptor proteins in the cilia; this generates the signal to the olfactory
lobe of the brain.
e. Odor information is then sent onto the olfactory cortex where odors are analyzed.
f. Odor information is projected to higher brain centers and affects emotions, thoughts and
behavior.
g. Recent cloning and molecular techniques have located genes in mammals that code for odor
reception.
h. Each of 500 to 1000 genes encodes a separate type of odor receptor.
i. Since mammals detect at least 20,000 different odors, each receptor must respond to several
molecules.
j. Each olfactory neuron projects to a characteristic olfactory bulb; the brain “maps” active
receptors.
k. Odors rise from the mouth to form the complex tastes beyond the four basic tastes.
l. Many terrestrial vertebrates possess an additional olfactory organ, the vomeronasal organ
(Jacobson’s Organ).
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D. Mechanoreception (Figure 13.21)
1. These receptors respond to touch, pressure, stretching, sound, vibration and gravity, and all forms of
motion.
2. Touch
a. The Pacinian corpuscle is a large mechanoreceptor for deep touch and pressure in mammalian
skin.
b. Each has a nerve terminus with a capsule of onion-like layers of connective tissue.
c. Pressure at any point on the capsule distorts the nerve ending, producing a graded receptor
potential.
d. Progressively stronger stimuli lead to stronger receptor potentials until a threshold current is
produced.
e. If pressure is sustained, the corpuscle adjusts to the new shape and no longer responds.
f. Insects have tactile hairs sensitive to both touch and vibration.
g. Most vertebrate touch receptors are gathered in “sensitive” areas—a redundant statement.
h. Each hair follicle has receptors sensitive to touch.
3. Pain and Pleasure
a. Pair receptors are unspecialized; these free nerve endings also respond to mechanical and heat
stimuli.
b. Pain fibers respond to small peptides, substance P and bradykinins, released by injured cells.
c. Chemical responses cause a slow pain response; a pin prick or burn causes a fast pain response.
d. Pain helps us avoid damage; pleasure is a stimulus to reinforce needed behaviors.
4. Lateral Line System of Fish and Amphibians
a. The lateral line detects wave vibrations and currents in water; it is a distant touch reception
system.
b. Neuromasts are receptor cells found in aquatic amphibians and some fishes.
c. They often occur in canals under the epidermis and opening at intervals to the surface.
d. Each neuromast has a collection of hair cells with the cilia embedded in a gelatinous cupula.
e. The cupula projects into the lateral line canal and bends in response to water disturbance.
f. The lateral line system is a major guide to fishes in locating predators and prey, and schooling.
5. Hearing (Figures 13.22-13.26)
a. The ear is a specialized receptor for detecting sound waves.
b. Most invertebrates inhabit a silent world; only some crustaceans, spiders and insects hear
sounds.
c. The specialized tympanic membrane of locusts, cicadas, crickets, grasshoppers and moths allow
them to detect a mate, rival male or predator.
d. Certain nocturnal moths have ears specialized for distant and high-intensity bat sounds.
e. The vertebrate ear evolved as a balancing organ, the labyrinth.
f. The labyrinth has two chambers, the saccule and utricle, and three semicircular canals.
g. In fish, the base of the saccule extended into a tiny pocket, the lagena.
h. In evolution, the fingerlike lagena evolved into the cochlea.
i. The outer ear collects sound waves and directs them down the auditory canal to the tympanum.
j. The middle ear is air-filled and contains three ossicles, the malleus, incus and stapes.
k. These bones conduct and amplify sound waves from tympanum to the oval window of the inner
ear.
l. The eustachian tube permits air pressure to equalize on both sides of the tympanic membrane.
m. The inner ear organ is the cochlea; it is coiled in mammals.
n. The cochlea is divided into three tubular canals running parallel with each other.
o. The vestibular canal has the oval window at its base.
p. The tympanic canal has its base closed by the round window.
q. The cochlear duct runs between these canals and has the organ of Corti, the sensory apparatus.
r. The organ of Corti has fine rows of hair cells from the base to the tip; over 24,000 are in a
human ear.
s. Each hair cell is connected with neurons of the auditory nerve.
t. Hair cells rest on the basilar membrane and are covered by the tectorial membrane.
u. Sound waves are transmitted from tympanum to oval window to basilar membrane with hair
cells.
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Place Hypothesis of Pitch Discrimination (Figure 13.27)
1) Georg von Bekesy proposed different areas of basilar membrane respond to different
frequencies.
2) At every sound frequency, there is a specific place on the basilar membrane hair cells
respond.
3) Isolated hair cells have been shown to respond to particular frequencies by location in the
cochlea.
4) Impulses from specific fibers are interpreted in the hearing center of the brain as particular
tones.
5) The loudness of a tone depends on the number of hair cells stimulated.
6) The quality of a tone is produced by the pattern of hair cells stimulated by sympathetic
vibrations.
6. Equilibrium (Figures 13.28, 13.29)
a. Statocysts
1) Invertebrates often detect gravity and low-frequency vibrations with statocysts.
2) Each statocyst is a sac lined with hair cells and containing a statolith.
3) Hairlike filaments of the sensory cells are activated by the shifting position of the statolith.
4) Statocysts occur in many invertebrates; from radiates to arthropods, statocysts are similar in
design.
b. Labyrinth
1) The labyrinth is the vertebrate organ of equilibrium.
2) It has two chambers, the saccule and utricle, and three semicircular canals.
3) The utricle and saccule are static balance organs that function like statocysts.
4) The semicircular canals are designed to respond to rotational but not linear acceleration.
5) Each canal has an ampulla with hair cells embedded in a gelatinous membrane.
6) Rotation causes the hair cell to be pressed back in the stable fluid and this distortion
produces the sensation of movement.
7) With three canals in different planes, acceleration in any direction provides a combination
of stimulations from each ampulla.
E. Photoreception (Figures 13.30-13.33)
1. Photoreceptors are light-sensitive.
2. They range from simple cells randomly scattered on the body surface to the complex eye of
vertebrates.
3. Arthropod Compound Eyes
a. These are composed of many independent units called ommatidia.
b. The eye of a bee contains about 15,000 and each views a separate narrow visual field.
c. This allows them to detect motion, but they do not have good resolution to see objects sharply.
4. Single-Lens Camera-Type Eye
a. The eyes of some annelids, molluscs and all vertebrates is built like a camera.
b. An image is focused on a light sensitive surface at the back of a light-tight chamber and lens
system.
c. The eyeball has three layers.
1) A tough outer white sclera provides support and protection.
2) A middle choroid coat has blood vessels for nourishment.
3) The light-sensitive retina lines the inside.
d. The cornea is a transparent anterior part of the sclera and it focuses the light that enters.
e. Light passes through the cornea, the pupil formed by the iris, and is further focused by the lens.
f. The lens is an oval disc that can be flattened by the ciliary muscles to focus the image on the
retina.
g. Watery fluid between the cornea and lens is the aqueous humor.
h. Vitreous humor fills the larger inner chamber between the lens and retina.
i. Retina
1) The retina has several cell layers.
2) The outermost layer is closest to the sclera and contains pigment cells.
3) The next layer contains rods and cones, the photoreceptor cells.
4) About 125 million rods and 1 million cones are in each human eye.
5) Rods provide colorless vision in dim light; cones detect colors in ample light.
v.
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
5.
6.
6) Next is a network of intermediate neurons that process and relay visual information to
ganglion cells that form the optic nerve.
7) Information from several hundred rods may converge on a single ganglion cell.
8) Cones, however, show little convergence.
9) The fovea centralis is a region of keenest vision near the center of a retina; it contains only
cones.
10) Visual acuity depends on the density of cones in the fovea.
11) Many birds have eight times the density of cones in this area, and far greater visual acuity.
Chemistry of Vision
a. Both rods and cones contain light-sensitive pigments known as rhodopsins.
b. Each molecule consists of a large protein enzyme, opsin and a small carotenoid molecule,
retinal.
c. When the rhodopsin molecule absorbs light, retinal changes shape.
d. Triggering the enzyme activity of opsin results in an excitatory cascade generating a nerve
impulse.
e. The amount of intact rhodopsin in the retina depends on the intensity of light reaching the eye.
f. A dark-adapted eye contains much rhodopsin and is sensitive to weak light.
g. In a light-adapted eye, much rhodopsin is broken down into retinal and opsin.
Color Vision (Figure 13.34)
a. Cones require 50-100 times more light for stimulation than rods to perceive color.
b. Nocturnal animals have pure rod retinas.
c. Purely diurnal animals, such as squirrels and some birds, have only cones and are blind at night.
d. In 1802, an English physician proposed that color vision was due to three kinds of
photoreceptors.
e. In the 1960s, researchers confirmed the function of red, green and blue photoreceptors.
f. Blue cones absorb light at 430 nm, green cones at 540 nm, and red cones at 575 nanometers
wavelength.
g. Variation in structure of opsin produces different visual pigments found in the rods and cones.
h. A comparison is made in the brain of differential excitement of cones, and the brain interprets
color.
i. Bony fishes and birds have very good color vision; amphibians lack color vision.
j. Most mammals are mostly color blind except for primates and squirrels.
Lecture Enrichment
1.
2.
3.
4.
5.
The concept of a nerve impulse as a change in polarity, but not the movement of ions as the impulse, can be
demonstrated by setting up a row of dominoes. In this analogy, as the dominoes fall the impulse moves quite
rapidly, but the individual dominoes stay in position. Setting the dominoes back up represents the sodium pump.
For students who have not had physics, the difference between the positive and negative pole of a battery may be
useful in representing a potential.
The introductory illustration of the impossibility of being able to perceive as another animal perceives becomes
clearly understandable as the various sensory systems are described.
The property of Pacinian corpuscle physiological “adaptation” can also be recognized by students who are sitting
in classroom chairs and are now unaware of the many pressure points they have with the hard chair edge, the belt
buckle, the seam in their jeans, etc.
Most students should have experienced and remembered elementary school recess where they spun around until
they became dizzy and fell down, and the world “felt” like it continued spinning. This can be used during
explication of the semicircular canal function.
Commentary/Lesson Plan
Background: Most students have sprayed an insect and watched it die with tremors representing the action described
in the text for inactivation of the enzyme acetylcholinesterase. Students are conscious of the various human sensory
systems, and examples can be readily drawn from their experiences.
Misconceptions: The “wave of negativity” that results in a nerve impulse is often visualized as the sodium ions
actually moving this distance themselves. Humans are very visual-oriented and students will often have great
difficulty understanding that many animals primarily orient by odors and live in a “world of smells.” We see a mouse
running a maze as a learning experience of turning left or right, but unless the track is cleaned each time, the mouse is
mainly cueing on its previous scent. Of their many senses, students will state “I can live without pain.” This fails to
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
recognize the critical role pain plays in providing humans and other animals with a sense of self, as is seen when the
sense of pain is lost in leprosy and a person wears away tissues.
Schedule:
HOUR 2 13.4. Sense Organs
HOUR 1 13.1. Neuron: Functional Unit of the Nervous
A. Stimuli
System
B. Classification of Receptors
A. Structure
B. Nature of the Nerve Impulse
C. Chemoreception
D. Mechanoreception
13.2. Synapses: Junction Points between Nerves
E. Photoreception
A. Function
13.3. Evolution of the Nervous System
A. Invertebrates: Development of
Centralized Nervous Systems
B. Vertebrates: Fruition of
Encephalization
ADVANCED CLASS QUESTIONS:
1. Would a species of insect ever produce a pheromone, but not have any ability to detect the pheromone?
2. What are the physiological and the evolutionary reasons that taste sensations are not all equal?
3. A Pacinian corpuscle quickly adjusts to a new shape and no longer responds, a property called “adaptation.” How
is this physiological “adaptation” also an evolutionary adaptation?
4. Why do ctenophores that drift in black ocean depths need statocysts?
5. Why do nighttime street scenes, except near the streetlights, actually appear to us to be shades of gray when we
know the objects in daytime have bright colors?
6. The lens adjustment to light and dark is relatively fast and yet, your ability to see when you enter a dimly lit room
adjusts and improves over a half-hour. What is the physiological basis of this?
Twelfth Edition Changes: There are only minor changes in this chapter.
Source Materials
[Bold = recommended; vendor abbreviations are provided in Appendix 1]
Action Potential Tutorial (INT), Mac
The Addicted Brain (FH), 26-min. video
Alcohol and Human Physiology (AIMS), 24-min. video, laserdisc
Alzheimer’s Disease: The Long Nightmare (FH), 19-min. video
Autonomic Nervous System (IFB), 17-min.
Autonomic Nervous System (IM), 29-min. video
Autonomic Nervous System (PH), 6-min.
Basic Ophthalmology (Q), Mac, Win CD
Bioethics Forums: Alzheimer Disease (CAM), Mac, Win CD
Biosensors (PHO), 32-min. video
Body Atlas: The Brain (AVP) (JLM), 30-min. video
Body Atlas: Now Hear This (AVP) (JLM), 30-min. video
Body Atlas: Taste and Smell (AVP) (JLM), 30-min. video
Body Atlas: Visual Reality (AVP) (JLM), 30-min. video
Body Language: Nervous System (PLP), Apple, MS-DOS, Mac
Body and Mind (Q), MS-DOS CD
Brain (IM), 29-min. video
Brain (FH), 23-min. video
The Brain (A-CPB), 8 1-hour videos
The Brain (IM), 50-min. video
Brain (NEB), 22-min. video [dissection]
Brain Dissection and Anatomy (IM), 22-min. video
Brain Games (SciT), Mac
The Brain and the Nervous System (PHO), 33-min. video
The Brain: Our Universe Within (IM), 2 25-min. videos
Brain Triggers: Biochemistry and Human Behavior (HRM), filmstrip or video
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
The Brain: Our Universe Within (IM), 2 25-min. videos
The Brain and Spinal Cord (AIMS), Mac, Win CD, 15-min. video, laserdisc
The Chemical Synapse Tutorial (INT), Mac
Cocaine and Human Physiology (AIMS), 20-min. video, laserdisc
Cochlear Anatomy: A Macintosh Tour (INT) (SciT), Mac
Comprehensive Review in Biology: Nervous and Hormonal Systems (Q), Mac, Win
Cycles of Life: Exploring Biology–Animal Structure (A-CPB), 30-min. video
Cycles of Life: Exploring Biology--The Neural Connection (A-CPB), 30-min. video
Designer Drugs and Human Physiology: Crack Cocaine, Methamphetamine (AIMS), 14-min. video, laserdisc
Designer Drugs and Human Physiology: PCP, Ecstasy, Fentanyl (AIMS), 19-min. video, laserdisc
Development of the Human Brain (FH), 40-min. video
Ear as a Sensory Organ (IFB), 23-min. video
The Ears and Hearing (EBE), 22-min. video
Ears and Their Function (ei), slides
Epilepsy (Q), Mac, Win CD
Experimental Psychology Data Simulation (OAK), MS-DOS and Mac
Exploring the Brain: The Newest Frontier (HRM), filmstrip or video
Exploring the Human Brain (BFA) (PHO), 18-min. video
Eye and Ear (IM), 29-min. video
Eye Dissection and Anatomy (IM), 16-min. video
Eyes and Ears (FH), 26-min. video
The Eyes and Seeing (EBE), 20-min. video
Eyes and Their Function (ei), slides
Flash: The Human Brain (also Neurons and the EEG) (PLP), Apple or MS-DOS
Frog Sciatic Nerve (INT), Mac
Glaucoma (MF), 13-min. video
Growing Old in a New Age–How the Body Ages (A-CPB), 1-hr. video
Growing Old in a New Age–Learning, Memory and Speed of Behavior (A-CPB), 1-hr. video
Growing Old in a New Age–Illness and Disability (A-CPB), 1-hr. video
Hearing (FH), 23-min. video
Heroin and Human Physiology (AIMS), 22-min. video, laserdisc
How Much Do You Smell? (FI), 50-min. film
The Human Brain (AIMS), Mac, Win CD, 14-min. video
The Human Body Series: The Brain (PHO), 16-min. video
The Human Body Series: Nervous System (PHO), 23-min. video
The Human Eye (IFB), 15-min. video
The Human Quest (FH), 4 58-min. videos
Human Vision (CAM), Mac, Win CD
The Hidden Universe: The Brain (CRM), 48-min. video
Incredible Voyage (CRM), 26-min. video
Inner Ear (FI), 11-min. film
Inside Information: The Brain and How It Works (FH), 58-min. video
Introduction to General Biology: The Human Body II (Q), Mac, DOS
Investigating the Nervous System (AIMS), Mac, Win CD, 20-min. video
Journeys to the Centers of the Brain (FH), 5 58-min. videos
Losing It All: The Reality of Alzheimer's (AVP), 60-min. video
MacRetina (INT) (SciT), Mac
Marijuana and Human Physiology (AIMS), 22-min. video, laserdisc
Marvels of the Mind (NGS), 23-min. video
Membrane Potential Problem Solver (TS), MS-DOS
Membrane Potential Tutorial (INT), Mac
Membrane Potentials (PLP), MS-DOS
Memory: Fabric of the Mind (FH), 28-min. video
The Mind as Healer (FH), 22-min. video
Mind's Eye (FI), 50-min. film
Mysteries of the Mind (FH), 58-min. video
NATURE: Inside the Animal Mind (WNET), 3-hr. video
Nature of the Nerve Impulse (FH), 15-min. video
317
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Nerve Hearing Loss (MF), 14-min. video
The Nerve Impulse (EBE) (ei), 22-min. video
Nerves (IM), 24-min. video
Nerves and Heartbeat Rate (BSCS Classic Inquiry) (MDA), videodisc
Nervous System (PHO) (IM) (NGS), 29-min. video
Nervous System (EBE), 17-min. video
Nervous System (PLP), MS-DOS
Nervous System and Its Functions (ei), slides
Nervous System: Decision (FH), 26-min. video
Nervous System: Nerves at Work (FH), 26-min. video
Nervous System: Our Talented Brain (FH), 26-min. video
The Neural Connection (IM), 30-min. video
Neuroanatomy Foundations Academic Version (INT), Mac
Neurobiology I: Excitatory Membranes (ei), slides
Neurobiology II: Neural Functions (ei), slides
The Nose—Structure and Function (EBE), 11-min. video
NOVA: The Brain Eater (NEB) (WGBH), 60-min. video
NOVA: Brain Transplant (NEB) (WGBH), 60-min. video
NOVA: Coma (NEB) (WGBH), 60-min. video
NOVA: Leprosy Can Be Cured (WGBH), 60-min. video
NOVA: Mystery of the Animal Pathfinders (MBI) (PHO) (WGBH), 60-min. video
NOVA: Mystery of the Senses–Hearing (Fish) (IM) (JLM) (MBI) (NEB) (WGBH), 60-min. video
NOVA: Mystery of the Senses–Smell (Fish) (IM) (JLM) (MBI) (NEB) (WGBH), 60-min. video
NOVA: Mystery of the Senses–Taste (Fish) (IM) (JLM) (MBI) (NEB) (WGBH), 60-min. video
NOVA: Mystery of the Senses–Touch (Fish) (IM) (JLM) (MBI) (NEB) (WGBH), 60-min. video
NOVA: Mystery of the Senses–Vision (Fish) (IM) (JLM) (MBI) (NEB) (WGBH), 60-min. video
NOVA: Secret of the Wild Child (NEB) (WGBH), 60-min. video
NOVA: Stranger in the Mirror (NEB) (WGBH), 55-min. video
Peripheral Nervous System (IFB), 19-min. video
The Senses (IM), 29-min. video
Senses (CBSC), Apple II, Mac, MS-DOS
Senses (CSG), Mac
Senses: Eyes and Ears (IFB), 26-min. video
Senses–5 Sense Organs (NEB), Apple, Mac, DOS
Senses: Physiology of Human Perception (PLP), Apple, MS-DOS, Mac
Senses: Skin Deep (FH), 26-min. video
Sensory World (CRM), 11-min. video
The Sexual Brain (FH), 28-min. video
Sight (FH), 23-min. video
SimNerv (THIEME), Mac, Win CD
SimPatch (THIEME), Mac, Win CD
The Skin as a Sense Organ (IFB), 12-min. video
Skin Deep (FH), 26-min. video
The Sleep Files (AVP), video set (9)
Smell (FH), 23-min. video
The Study of Memory (FH), 74-min. video
Systems of the Body: An Introduction (PHO), filmstrip
Taste (FH), 23-min. video
Teaching Modules from "The Brain" (CPB), 30 segments on 2 VHS videos or 4 videodiscs
Think Tank (INT), Mac
Touch (FH), 23-min. video
Touch, Taste, and Smell (ei), slides or filmstrip
Transmission of the Nerve Impulse (PLP), MS-DOS
Ultrascience: Mind Games (AVP), 30-min. video
Visual Reality (IM), 25-min. video
318
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Copyright © 2005 – The McGraw-Hill Companies srl
CHAPTER
14
CHEMICAL COORDINATION
CHAPTER OUTLINE
34.1.
Hormones and Mechanisms of Hormone Action (Figure 14.1)
A. Overview
1. Along with the nervous system, the endocrine system controls the body’s activities.
2. It communicates by chemical messengers called hormones.
3. Hormones are released into the blood and transported throughout the body.
4. Only in target cells do they initiate a physiological response.
5. Endocrine Glands
a. Endocrine glands are small, well-vascularized ductless glands with clustered cells.
b. They have no ducts and they must secrete hormones into the blood.
c. Endocrine glands capture raw materials from the bloodstream and secrete hormones into it.
d. In contrast, exocrine glands secrete fluids through the ducts.
6. The classical definitions are being blurred since some hormones may not enter the general circulation.
7. Other tissues secrete some hormones such as insulin and cytokines.
8. Some hormones function as neurotransmitters in the brain or as local tissue factors (parahormones).
9. Compared with nervous impulses, hormones are slower acting because the chemicals must reach the
tissues and diffuse across membranes.
10. However, hormonal responses in general are long lasting, for many minutes or days.
11. Endocrine control is superior if sustained effort is required for metabolism, growth or reproduction.
12. There is not a sharp distinction between nervous and endocrine systems; endocrine glands often
receive nerve stimulation and hormones may act on the nervous system.
13. All hormones are low-level signals; a hormone rarely exceeds one billionth of a 1M concentration.
14. Some target cells respond to concentrations one thousandth less than this.
15. Some hormones such as growth hormone affect most, if not all cells.
16. When only select cells are affected, this is due to receptor molecules only on these target cells.
17. Cells that do not respond to a hormone lack the specific receptors.
18. The two kinds of receptors are membrane-bound receptors and nuclear receptors.
B. Membrane-Bound Receptors and the Second Messenger Concept (Figure 14.2)
1. Many hormones are peptide hormones that are too large to pass through cell membranes.
2. These hormones, often amino acid derivatives, bind to receptor sites on the surface of target cells.
3. They are first messengers that cause activation of a second messenger system in the cytoplasm.
4. Each works by a specific kinase that causes activation or inactivation of rate limiting enzymes that
modify the direction and rate of cytoplasmic processes.
5. A single hormone molecule may activate thousands of second messengers—the message is amplified.
6. Second messenger systems that participate in hormone actions include cyclic AMP, cyclic GMP,
Ca++/calmodulin, inositol-triphosphate and diacylglycerol.
7. Cyclic AMP was discovered early and is known to mediate actions of many peptide hormones
including parathyroid hormone, glucagon, ACTH, thyrotropic hormone, melanophore-stimulating
hormone, vasopressin and epinephrine.
8. Recent evidence suggests that lipid-soluble hormones, such as estrogen, may also possess membranebound receptors that activate second messenger systems in the same way as peptide hormones,
providing multiple and complex control of target cells.
C. Nuclear Receptors
1. Steroid hormones are lipid-soluble and readily diffuse through cell membranes.
2. Steroid hormones include estrogen, testosterone and aldosterone.
3. They may be located in either the cytoplasm or nucleus but their ultimate site of activity is the nucleus.
4. A hormone-receptor complex, known as a gene regulatory protein, activates or inhibits specific genes.
5. As a result, gene transcription is altered.
6. Stimulation or inhibition of mRNA formation modifies production of key enzymes.
7. Peptide hormones act indirectly through second messengers; steroids work directly through genes.
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
14.2.
14.3.
D. Control of Secretion Rates of Hormones (Figure 14.3)
1. Hormones influence cellular functions by altering rates of biochemical processes.
2. The action of hormones may be to affect enzyme activity and alter cell metabolism, change membrane
permeability, regulate synthesis of cell proteins, or stimulate release of hormones from other glands.
3. This is a dynamic process that must be regulated, not just activated.
4. Release of a hormone into the blood depends on its rate of secretion and the rate it is inactivated.
5. Endocrine glands must receive information about the level of its own hormone in the plasma.
6. Many hormones are controlled by negative feedback systems between glands and target cells.
7. The hypothalamus secretes CRH that stimulates the pituitary to release ACTH, which stimulates the
adrenal gland to secrete cortisol; increases in blood ACTH inhibit release of CRH.
8. Such “closed loop” feedback systems are more complex because the nervous system or metabolites or
other hormones may alter them.
9. Some oscillations in hormone output result from positive feedback where output escalates rather than
remains around a set point.
9. Such mechanisms control birth and ovulation; they must have natural shutoff mechanisms.
10. During positive feedback the signal (or output of the system) feeds back to the control system and
causes an increase in the initial signal. In this way the initial signal becomes progressively amplified
to produce an explosive event.
Invertebrate Hormones (Figure 14.4)
A. Neurosecretory Cells and Molting
1. In metazoans, a main source of hormones is neurosecretory cells, nerve cells that secrete hormones.
2. Neurosecretions or neurosecretory hormones are placed directly in the circulation.
3. They link the nervous and endocrine systems.
4. This is well studied in the process of molting during metamorphosis in insects.
5. Two hormones control molting.
a. Molting hormone, or ecdysone, is produced by the prothoracic gland.
b. Juvenile hormone is produced by the corpora allata.
c. Ecdysone is controlled by prothoracicitropic hormone (PTTH) produced in the brain and
transported by axons to the corpora allata where it is stored.
d. Ecdysone acts directly on chromosomes and favors development of adult structures.
e. Juvenile hormone favors larval features and predominates at each larval stage.
f. Juvenile hormone decreases at the final stage, allowing metamorphosis to the adult stage.
g. Analogs of juvenile hormone may be able to replace some insecticides by blocking development.
Vertebrate Endocrine Glands and Hormones
A. Hormones of the Hypothalamus and Pituitary Gland (Figures 14.5-14.7)
1. Structure
a. The pituitary gland, or hypophysis, is at the floor of the brain above the roof of the mouth.
b. The anterior pituitary is derived from the roof of the mouth.
c. The posterior pituitary arises from the ventral portion of the brain, the hypothalamus, and is
connected to it by a stalk, or infundibulum.
d. The anterior pituitary’s only connection to the hypothalamus is a special portal circulatory system.
e. The neurosecretory cells of the hypothalamus therefore have a link to the anterior pituitary gland.
2. Hypothalamus and Neurosecretion
a. The pituitary influences most hormonal activities but is controlled by centers in the hypothalamus.
b. Groups of neurosecretory cells in the hypothalamus manufacture releasing hormones and release
inhibiting hormones or factors.
c. These neurohormones travel down nerve fibers to endings where they enter a capillary network.
d. The pituitary portal system takes them directly to the anterior pituitary.
e. The hypothalamic hormones stimulate or inhibit various anterior pituitary hormones.
f. Some hormones have been isolated and characterized; others are tentative.
3. Anterior Pituitary (Table 14.1)
a. The anterior pituitary has an anterior lobe and an intermediate lobe (absent in humans).
b. The anterior lobe produces six hormones and the intermediate produces one.
c. Four hormones are tropic hormones that regulate other endocrine glands.
d. Thyroid-stimulating hormone (TSH) stimulates production of thyroid gland hormones.
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Copyright © 2005 – The McGraw-Hill Companies srl
e.
f.
g.
Follicle-stimulating hormone (FSH) promotes egg production or sperm production.
Luteinizing hormone (LH) induces ovulation and corpus luteum and sex steroid production.
Adenocorticotropic hormone (ACTH) increases production and secretion of steroid hormones
from the adrenal cortex.
h. Prolactin is a protein hormone that prepares mammary glands for lactation and milk production.
i. Prolactin is also implicated in parental behavior of a wide variety of vertebrates, a mediator of the
immune system, and a factor in formation of new blood vessels.
j. Growth hormone (GH or somatotropin) governs cell mitosis, synthesis of mRNA, and metabolism.
k. Growth hormone acts indirectly through a polypeptide hormone, insulin-like growth factor (IGF).
l. The intermediate lobe produces melanocyte-stimulating hormone (MSH) that promotes dispersion
of pigment in cells in bony fishes, amphibians and reptiles.
m. In birds and mammals, MSH is produced in the anterior pituitary and has unclear roles.
4. Posterior Pituitary
a. The hypothalamus is source of two hormones of the posterior lobe of the pituitary.
b. The hormones form in neurosecretory cells in the hypothalamus and are released through axons
into the blood capillaries of the posterior lobe.
c. The posterior lobe is not therefore an endocrine gland but a storage and release center.
d. Both oxytocin and vasopressin are chemically similar; both are octapeptides.
e. Both hormones are fast acting, producing a response within seconds of their release.
f. Oxytocin
1) Oxytocin stimulates contraction of uterine smooth muscle during birth.
2) It can be used to induce delivery.
3) Oxytocin also triggers milk ejection by mammary glands in response to suckling.
4) Oxytocin in monogamous voles is also involved in pair-bonding in both sexes.
g. Vasopressin
1) Vasopressin acts on collecting ducts of the kidney to increase water absorption.
2) It is also called antidiuretic hormone.
3) It increases blood pressure by constricting smooth muscles of arterioles.
4) Vasopressin also acts centrally to increase thirst and drinking.
h. All jawed vertebrates secrete two posterior lobe hormones similar to oxytocin and vasopressin.
i. Amino acid substitutions vary the octapeptides but their actions are analogous.
j. Vasotocin
1) This is a widely distributed octapeptide and the parent hormone from which others evolved.
2) Vasotocin is not found in mammals, but plays a water-conserving role in birds and reptiles.
3) In amphibians is increases permeability of the skin and stimulates water reabsorption from the
urinary bladder.
B. Pineal Gland
1. In all vertebrates, the diencephalon gives rise to a sac-like pineal complex.
2. It lies just below the skull in a mid-line position.
3. In ectothermic vertebrates the pineal complex has glandular tissue and photoreceptors.
4. As a sensory organ, it is involved in pigments responses and light-dark biological rhythms.
5. In lampreys, some amphibians, lizards and the tuatara it resembles a third eye in structure.
6. In birds and mammals, the pineal complex is entirely glandular and forms the pineal gland.
7. It produces melatonin in a cycle with exposure to light; production is highest at night.
8. In nonmammalian vertebrates, it maintains circadian rhythms and provides a biological clock.
9. In mammals, the suprachiasmatic nucleus of the hypothalamus is the primary circadian pacemaker.
10. In mammals with reproduction keyed to photoperiod, melatonin regulates gonadal activity.
11. Long-day breeders have reproduction suppressed during winter months.
12. Short-day breeders increase reproductive activity in the fall.
13. Seasonal affective disorder, jet lag and shift-work all are linked to melatonin rhythms.
C. Brain Neuropeptides
1. A growing list of hormone-like neuropeptides has been discovered in the central and peripheral
nervous systems of both vertebrates and invertebrates.
2. Over 40 neuropeptides have been located using immunological techniques in mammals.
3. Many are both hormones carrying signals to gland cells, and neurotransmitters relaying nerve signals.
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4.
5.
6.
7.
Both oxytocin and vasopressin occur in widespread sites in the brain.
Unrelated to its antidiuretic function, vasopressin can increase learning and memory.
Gastrin and CCK have been isolated in cerebral cortex and CCK functions in control of feeding.
Endorphins and Enkephalins
a. These neuropeptides bind with opiate receptors and influence perception of pain and pleasure.
b. They are also found in brain circuits that control blood pressure, body temperature, etc.
c. They are derived from the same prohormones that give rise to ACTH and MSH.
D. Prostaglandins and Cytokines
1. Prostaglandins
a. Prostaglandins were discovered in seminal fluid in the 1930s.
b. They are derived from long-chain unsaturated fatty acids.
c. First thought to be produced only in the prostate, prostaglandins are in nearly all mammalian
tissues.
d. They have diverse actions in different tissues but have more effect on smooth muscle.
e. They regulate vasodilation and vasoconstriction of blood vessels.
f. They stimulate contraction of the uterine smooth muscle during childbirth.
g. Overproduction of prostaglandins may contribute to dysmenorrhea.
h. Prostaglandins also intensify pain in damaged tissues and mediate inflammation, and fever.
2. Cytokines
a. This large group of hormones mediates communication between cells during the immune
response.
b. Cytokines affect the cells that secrete them, nearby cells, and distant target cells.
c. One cytokine that activates some cells to divide may suppress division of other target cells.
d. Cytokines are also involved in formation of blood.
E. Hormones of Metabolism
1. Thyroid Hormones (Figures 14.8-14.10)
a. Hormones never initiate enzymatic processes but can alter their rate.
b. The thyroid is a large endocrine gland located in the neck of vertebrates.
c. The thyroid contains thousands of tiny sphere-like follicles that produce and store hormones.
d. The thyroid concentrates iodine; it contains well over half the iodine in the body.
e. The thyroid produces triiodothyronine (T3) with three iodine atoms and thyroxine (T4) with four.
f. T4 is produced in greater amounts but T3 is the more physiologically active.
g. T4 is considered a precursor to T3.
h. Their most important actions are to promote normal growth and development of the nervous
system and to stimulate metabolic rate.
i. Undersecretion of thyroid hormones in fish, birds and mammals dramatically impairs growth.
j. Oversecretion of thyroid hormones causes premature development.
k. Frogs and toads transform from tadpole to adult when the thyroid becomes active.
l. In birds and mammals, thyroid hormones control oxygen consumption and heat production.
m. The thyroid is critical in maintaining a normal level of metabolism in homeotherms.
n. Thyroid hormones reduce efficiency of cellular oxidative phosphorylation to produce more heat.
o. Therefore, many cold-adapted mammals eat more food in winter and more is converted to heat.
p. Thyrotropic hormone from the anterior pituitary governs synthesis and release of these hormones.
q. In turn, the hypothalamus controls TSH production with thyrotropin-releasing hormone (TRH).
r. The TSH-TRH balance is a case of simple negative feedback between hypothalamus and pituitary.
s. Goiter
1) Goiter is enlargement of the thyroid gland due to deficiency of iodine in food and water.
2) By striving to produce thyroid hormone, the gland grows much larger and swells the neck.
3) Goiter is prevented in the U.S. by adding iodine to salt; it still exists in mountainous regions.
2. Hormonal Regulation of Calcium Metabolism (Figures 14.11, 14.12)
a. Human parathyroid glands occur in two pairs; they vary in number and position in other animals.
b. Associated with the thyroid, they were discovered when removal of the “thyroid” caused death.
c. In birds and mammals, removal of these glands causes blood calcium levels to drop.
d. Continued decrease in calcium leads to excitability, muscle spasms, tetany and death.
e. Parathyroid hormone (PTH) is essential to maintenance of calcium homeostasis.
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Copyright © 2005 – The McGraw-Hill Companies srl
f.
g.
h.
i.
3.
4.
5.
Although 98% of calcium is in bone, this living tissue is constantly being dissolved and rebuilt.
Three hormones coordinate the absorption, storage, and excretion of calcium ions.
If blood calcium decreases slightly, the parathyroids increase secretion of PTH.
PTH stimulates osteoclasts to dissolve bone adjacent to these cells, releasing calcium and
phosphate into the blood and returning calcium levels to normal.
j. PTH also decreases the rate calcium is excreted by the kidney.
k. PTH increases production of the hormone 1,25-dihydrovitamin D.
l. Vitamin D
1) Vitamin D is a dietary requirement, but can also be synthesized in the skin by sunlight.
2) Vitamin D converts by a two-step oxidation to a hormonal form: 1,25-dihydroxyvitamin D.
3) Vitamin D deficiency causes rickets, a disease of low blood calcium and weak bones.
m. Calcitonin
1) Calcitonin is secreted by C cells in the mammal thyroid gland and in the ultimobranchial
gland of other vertebrates.
2) It is released in response to elevated levels of calcium in the blood.
3) It rapidly suppresses calcium withdrawal from bone, decreases intestinal absorption of
calcium and increases excretion of calcium by the kidneys.
4) Calcitonin protects the body against a rise in blood calcium, just as PTH protects against loss.
5) However, removal of the thyroid (and therefore the C cells) does not affect homeostasis.
Hormones of the Adrenal Cortex (Figures 14.13, 14.14)
a. The mammalian adrenal gland is a double gland composed of unrelated glandular tissue.
b. The outer region is the adrenal cortex; the inner region is the adrenal medulla.
c. In non-mammal vertebrates, the equivalent tissues are organized quite differently.
d. 30 compounds have been isolated from adrenocortical tissue; only a few are steroid hormones.
e. Many compounds are intermediates in the synthesis of hormones from cholesterol.
f. Corticosteroid hormones are grouped into glucocorticoids and mineralocorticoids.
g. Glucocorticoids
1) Cortisol and corticosterone are involved with food metabolism, inflammation and stress.
2) They promote synthesis of glucose from amino acids and fats by gluconeogenesis.
3) This increases glucose in the blood as a quick energy source for muscles and nerve tissues.
4) They also decrease the immune response and are used to treat inflammatory diseases.
5) ACTH controls synthesis and secretion; ACTH is controlled by corticotropin-releasing
hormone (CRH) of the hypothalamus.
6) A negative feedback relationship exists between CRH, ACTH, and adrenal cortex.
h. Mineralocorticoids
1) Mineralocorticoids are corticosteroids that regulate salt balance.
2) Aldosterone is the most important steroid in this group.
3) Aldosterone promotes tubular reabsorption of sodium and secretion of potassium in kidneys.
4) This helps many animals since sodium is often in short supply and potassium is in excess.
5) The salt-regulating action is controlled by the renin-angiotensin system and by blood levels.
i. Adrenocortical tissue also produces androgens that act similar to testosterone.
Hormones of the Adrenal Medulla
a. Adrenal medullary cells secrete epinephrine (adrenaline) and norepinephrine (noradrenaline).
b. Adrenal medulla is embryologically the same tissue that gives rise to neurons of the autonomic
nervous system and can be considered a very large sympathetic ganglion.
c. Norepinephrine serves as a neurotransmitter at the endings of sympathetic nerve fibers.
d. Release of epinephrine produces the same emergency responses as the sympathetic system.
e. Both hormones moderate constriction of arterioles, mobilization of liver glycogen and fat stores,
oxygen consumption, blood coagulation, and gastrointestinal tract.
Insulin and Glucagon from Islet Cells of the Pancreas (Figures 14.15, 14.16)
a. The pancreas is both an exocrine and endocrine gland.
b. Scattered among the exocrine portion are small islets of Langerhans.
c. This endocrine portion only constitutes 1-2% of the total weight of the pancreas.
d. In the islets, alpha cells produce glucagon and beta cells produce insulin.
e. Insulin and glucagon have antagonistic actions on the metabolism of carbohydrates and fats.
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
f.
g.
h.
i.
j.
k.
6.
7.
All body cells except neurons require insulin for entry of glucose into body cells.
Without insulin, the level of glucose in the blood rises to abnormal levels or hyperglycemia.
Insulin deficiency also inhibits uptake of amino acids by skeletal muscle.
Body cells starve while glucose exceeds the kidney’s ability to reabsorb it.
Diabetes mellitus afflicts nearly 5% of the human population.
Banting and Best Experiment of 1921
1) Earlier researchers had determined that removing the pancreas caused diabetes.
2) Isolation had been impossible because digestive enzymes destroyed the hormone in surgery.
3) Banting and Best tied off the pancreatic ducts of dogs and allowed the exocrine portion to
degenerate.
4) This allowed removal and isolation of insulin without the digestive enzyme destruction.
5) This led to extraction of insulin for treatment of human diabetes.
l. Glucagon has effects on carbohydrates and fat metabolism opposite of insulin.
m. Glucagon raises blood glucose level by converting liver glycogen to glucose.
n. Not all vertebrates have the same response to glucagon and insulin and some lack glucagon.
Growth Hormone and Metabolism
a. Growth Hormone (GH)
1) GH is very important in young animals during growth and development.
2) It acts directly to increase bone length and density by cell division and protein synthesis.
3) GH releases fat from adipose tissue stores and glycogen from liver to support metabolism.
4) GH is diabetogenic; oversecretion leads to an increase in blood glucose and insulin
insensitivity or diabetes.
5) If produced in excess, GH causes giantism; a deficiency in childhood leads to dwarfism.
6) GH also acts indirectly via stimulation of insulin-like growth factor (IGF) from the liver.
The Newest Hormone-Leptin
a. In 1994, the ob gene was found to code for a hormone leptin produced in white fat cells.
b. Receptors have been found in many cells but are primarily in the hypothalamus.
c. Leptin regulates eating behavior and energy balance in the feedback system that informs the brain
of energy status in the body.
d. Blood plasma levels of leptin are similar to insulin, another feedback signal.
Lecture Enrichment
1.
2.
3.
The effect of estrogen and testosterone can be related to the broad shoulders, head and other features of a bull
compared to the more-marbled meat and female-like development of a steer that develops without normal
testosterone levels.
We tend to think of adaptations as being external morphological characteristics, but the biochemistry that shifts cells
to more heat production is a biochemical adaptation vital to survival, just as the special digestive enzymes that allow
an animal to eat a plant toxic to most others.
The history of Bayliss and Starling’s work as well as the classic experiments of Banting and Best are fundamental
examples of research procedure and application. They provide students with background and insight on how
pioneer experiments are performed, and also provide a foundation of understanding on the critical role animal
research has played in solving both pure and medical research problems. Endocrinology is nearly 100 percent based
on lab animal research and an instructor can provide additional examples, in both readings and lecture, from the
history of physiology. Students who do not have an understanding of this extensive laboratory basis for
endocrinology will be susceptible to claims being made that such work was not central or even necessary to this
science.
Commentary/Lesson Plan
Background: Nearly all students’ experiences with hormones will center on the sex hormones, testosterone and
estrogens. For rural students, the effects of these hormones are quite dramatically seen in the different structuring of
bulls, cows, steers, etc. Women will be familiar with the action of estrogen creams for reducing hair growth and keeping
the skin smooth.
Misconceptions: Hormones and the endocrine system are closely associated with puberty and sex due to society’s
allusion to hormones and adolescent development, etc.; it is therefore necessary to paint the full picture where sex
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Copyright © 2005 – The McGraw-Hill Companies srl
hormones are a relatively minor although interesting small sample. The only other examples given in general biology
textbooks are usually under- or over-secretion problems which likewise presents a “freakish” perspective; an instructor
will have to work hard to normalize the vital role of endocrines. Because we speak of “estrogen” as if it was just one
molecule, students may not recognize there are three common natural estrogen molecules in humans and a growing
number of eco-estrogens in the environment. Due to dietary advertisements, “cholesterol” is often seen by the public as
something that is always bad and something we can live without; this error can be addressed under coverage of steroid
hormones.
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Schedule:
HOUR 1 14.1. Hormones and Mechanisms of
HOUR 2 14.3. Vertebrate Endocrine Glands and Hormones
Hormone Action
A. Hormones of the Hypothalamus and
A. Overview
Pituitary Gland
B. Membrane-Bound Receptors and the
B. Pineal Gland
Second Messenger Concept
C. Brain Neuropeptides
C. Nuclear Receptors
D. Prostaglandins and Cytokines
D. Control of Secretion Rates of Hormones
E. Hormones of Metabolism
14.2. Invertebrate Hormones
A. Neurosecretory Cells and Molting
ADVANCED CLASS QUESTIONS:
1. An effect of thyroid hormones is the reduced efficiency of cellular phosphorylation. Why would evolution ever
select for a less efficient metabolism?
2. You notice your urine is milky colored. You add a drop of weak vinegar and it immediately clarifies. What is in
your urine that makes it milky? What hormone imbalance(s) could cause this?
Twelfth Edition Changes:
1.
2.
3.
4.
5.
Minor changes have been made to this chapter:
Recent evidence suggests that lipid-soluble hormones, such as estrogen, may also possess membrane-bound
receptors that activate second messenger systems in the same way as peptide hormones, providing multiple and
complex control of target cells.
During positive feedback, the signal (or output of the system) feeds back to the control system and causes an
increase in the initial signal. In this way the initial signal becomes progressively amplified to produce an
explosive effect.
Recent data suggest that steroid abuse among adolescents is increasing.
The exact role of insulin-dependent glucose transporters in the brain is not clear, but insulin is important in
central regulation of food intake and body weight.
Recent evidence suggests that leptin is more important during times of lower food, and consequently, energy
availability.
Source Materials
[Bold = recommended; vendor abbreviations are provided in Appendix 1]
Animal Hormones I: Principles and Functions (ei), slides or video
Biochemistry of the Immune System (CAM) (CBSC), Apple II, Mac, MS-DOS
Biochemistry of Hormones (CBSC) (ei) Apple II, Mac and MS-DOS
Body Atlas: Glands and Hormones (AVP) (JLM), 30-min. video
Chemistry of Life: Hormones and the Endocrine System (FH) (HRM), video
The Chemistry of Life: Hormones and the Endocrine System (HRM), slides
Comprehensive Review in Biology: Nervous and Hormonal Systems (Q), Mac, Win
Cycles of Life: Exploring Biology–Endocrine
Control: Systems in Balance (A-CPB), 30-min. video
Endocrine Control: Systems in Balance (IM), 30-min. video
Endocrine Glands (IM), 29-min. video
The Endocrine System (GA), 48-min. video
The Endocrine System (EBE) (IM), 21-min. video
Endocrinology Data Simulation (OAK), MS-DOS and Mac
Glands and Hormones (IM), 25-min. video
Graphic Human A & P Tutor: Endocrine System (PLP), MS-DOS
Hormones and the Endocrine System (IM), 45-min. video
Hormones: Messengers (FH), 26-min. video
Human Body Series: Endocrine System (PHO), 16-min. video
Insect Hormones—The Control of Moulting (Biology: Form and Function) (A-CPB) (IM), 24-min. video
Introduction to General Biology: The Human Body II (Q), Mac, DOS
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Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
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Messengers (FH), 26-min. video
Minimizing Long Term Complications of Diabetes (MF), 12-min. video
327
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Copyright © 2005 – The McGraw-Hill Companies srl
CHAPTER
15
ANIMAL BEHAVIOR
CHAPTER OUTLINE
15.1.
15.2.
15.3.
Science of Animal Behavior
A. Ethology (Figure 15.1)
1. The study of animal behavior as a science had its roots in the 1872 work of Charles Darwin.
2. Questions about how animals behave ask about physiological functions or proximate causation.
3. Questioning why animals behave a certain way as selected adaptations asks about ultimate causation.
4. Comparative psychology attempts to find general laws of behavior that apply across species.
5. Ethology is the science of animal behavior in the animal’s natural habitat.
6. A central theme of ethology is that behavioral traits can be isolated and measured and they have
evolutionary histories.
7. Sociobiology is the ethological study of social behavior and originated with E.O. Wilson’s 1975 book.
8. Social behavior is reciprocal communication of a cooperative nature that permits a group of organisms of
the same species to become organized and is represented by four “pinnacles.”
a. Colonial invertebrates, such as the Portuguese man-of-war, are tightly knit composites of individual
organisms.
b. Social insects such as ants, bees and termites have developed sophisticated systems of communication.
c. Dolphins, elephants and some primates, have highly developed social systems.
d. Humans have a unique social behavior.
9. Behavioral ecology focuses on individual behavior that maximizes reproductive success and studies mate
choice, foraging, parental investment, etc.
10. Much of the work by comparative psychologists and ethologists can be found under the discipline of
behavioral ecology.
Describing Behavior: Principles of Classical Ethology (Figures 15.2-15.4)
A. Early Work
1. The work of Konrad Lorenz and Niko Tinbergen laid down basic concepts in animal behavior.
2. What appears to be intelligent retrieval of an egg by a goose can be a “fixed pattern” behavior.
3. Such predictable sequences are called stereotypical behaviors.
4. Lorenz labeled any stimulus that triggered a certain innate behavior as a releaser.
5. If the animal responded to just one specific aspect of the releaser, this was a sign stimulus.
6. As an example, an alarm call of an adult bird may release a freeze response in a chick.
7. Tinbergen’s male stickleback fish became aggressive at the sign of another male’s red flank.
8. These automatic programmed responses are most efficient in wild conditions that do not pose the
unusual and artificial conditions set up by the researchers.
Control of Behavior (Figures 15.5, 15.6)
A. Innate Behavior
1. Invariable and predictable stereotyped behaviors are inherited or innate.
2. Although the behavior is independent of learning, it depends on interactions during development.
3. Programmed behavior is important for survival, especially when animals do not know their parents.
4. Programmed behavior can equip an animal for immediate response to the world at birth or hatching.
5. More complex animals with longer lives have more time for social interactions and learning.
B. Genetics of Behavior
1. Hereditary transmission of most innate behaviors is complex with many interacting genes.
2. However, some behavioral differences within species show simple Mendelian transmission.
3. Honeybee Hygiene
a. Honeybees are susceptible to a bacterial disease called American foulbrood.
b. If bees remove the dead larvae from the hive, they reduce the chance of infection spreading.
c. A strain of bees, called “hygienic,” uncaps cells containing rotten larvae and carries them out.
d. The two components of the behavior are removal of cell caps and removal of larvae.
e. Individuals homozygous for a recessive allele u at one gene perform uncapping behavior.
f. Individuals homozygous for recessive allele r at a second gene perform removal behavior.
g. Hygienic bees were crossed with nonhygienic bees; all heterozygous hybrids were nonhygienic.
h. A backcross with hygienic strains produced a one-quarter hygienic portion, one-quarter that did
not uncap but would remove bees, and one-quarter that uncapped but did not remove dead larvae.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
4.
5.
15.4.
Most inherited behaviors do not show simple segregation, but show an intermediate behavior.
Cross-breeding of lovebirds that carried nest material either in the beak or in the feathers produced
hybrids that had a confused carrying behavior.
C. Learning and the Diversity of Behavior (Figures 15.7, 15.8)
1. Learning is the modification of behavior through experience.
2. The marine opisthobranch snail Aplysia has provided an excellent experimental animal for learning.
a. When its siphon is prodded, the snail withdraws its gills for protection.
b. If repeatedly prodded, it soon ignores the stimulus, a behavior modification called habituation.
c. If a noxious stimulus is added to the prodding, it is sensitized and rapidly withdraws its gills.
d. These behaviors have been traced to nervous pathways, connecting sensory neurons to motor
neurons that control the withdrawal muscles.
e. Repeated stimulations diminished release of synaptic transmitter from sensory neurons.
f. Sensory neurons continued to fire, but with less neurotransmitter the system was less responsive.
g. Sensitization involved action of a facilitating neuron that was stimulated by the noxious agent and
increased the amount of transmitter released by the siphon sensory neurons.
h. This study showed that strengthening or weakening the gill-withdrawal reflex involved changes in
the levels of transmitter in existing synapses.
3. More complex kinds of learning may involve formation of new neural pathways and connections as
well as changes in existing circuits.
4. Imprinting (Figures 15.9, 15.10)
a. Imprinting imposes a stable behavior in a young animal by exposure to particular stimuli during a
critical period in development.
b. A newly hatched or duckling follows its mother; if isolated, it follows the first large object it sees.
c. Konrad Lorenz hand-reared goslings and they imprinted on him.
d. There is only a brief sensitive period when imprinting can occur; the bond then lasts for life.
5. Bird Songs Learned During a “Critical Window”
a. The songs of sparrows are important territorial calls and rely partially on learning.
b. If a baby bird is reared in isolation, it sings a rudimentary song.
c. The sparrow must hear a normal bird song in a critical period 10-50 days after hatching.
d. However, the young sparrow does not learn the songs of other species of birds during this time.
Social Behavior (Figure 15.11)
A. Definitions
1. Any response of one animal to another animal of the same species is a social behavior.
2. Two rival males fighting for possession of a female is a social interaction.
3. Moths swarming around a light, or trout in a cold portion of a stream are not social behaviors, but are
merely individuals responding to an environmental cue.
4. Social aggregations depend upon signals from the animals themselves.
5. Among some animals, breeding may be the only adult social behavior.
6. Other animals form strong monogamous relationships for life.
7. Mother mammals and birds often form social bonds with their young until they are fledged or weaned.
B. Advantages of Sociality (Figures 15.12, 15.13)
1. Living together provides both passive and active defense; they are safer in a group than they are alone.
2. In a breeding colony of gulls, an alarm call brings many to attack the predator en masse.
3. Prairie dogs live in a loose group and benefit from the extra eyes, ears and noses of others for warning.
4. The more animals there are in a group, the less likely an individual within the group will be eaten.
5. Sociality brings together males and females and synchronizes reproductive behavior.
6. In colonial birds, the sounds and displays trigger pre-reproduction endocrine changes in the birds.
7. Living in close quarters, a bird colony conspires to defend young and increase survival.
8. Social organization also benefits in cooperation in hunting for food, huddling for mutual protection
from severe weather, opportunities for division of labor and the potential for learning and transmitting
useful information through the society.
9. Transfer of innovative behaviors is illustrated in the case of Imo and fellow macaques on a Japanese
beach; her discoveries of washing potatoes and wheat-sifting soon became common in the troop.
10. Social living has disadvantages.
a. Camouflaged individuals survive predators by being dispersed.
b. Large predators need large amounts of food.
c. The ecological situation determines if a solitary or social strategy is better.
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Copyright © 2005 – The McGraw-Hill Companies srl
C. Aggression and Dominance (Figures 15.14-15.16)
1. Although social species must cooperate, each looks out for their own interests.
2. This includes competition for food, sexual mates, or shelter when any of these are limited.
3. Aggression is an offensive physical action, or threat, to force others to abandon something.
4. Agonistic behaviors are a broader category including any activity related to fighting.
5. Animals reserve their dangerous weapons for securing prey and do not use them on their own species.
6. Animal aggression within a species involves symbolic or ritualized displays that avoid injury or death.
7. A ritualized display is a behavior that has been modified through evolution to make it effective in
serving a communicative function.
8. A wide array of animal “fights” involve ritual jousts: fiddler crab claw battles, male rattlesnake dances,
puffing fish, giraffe “necking,” and bighorn sheep butting heads.
9. The loser of a ritualized battle often runs away or signals defeat by a subordination ritual.
10. The victor in such competition has access to the contested food, mates or territory.
11. Schjelderup-Ebbe first described the dominance hierarchy of chickens from the pecking order that
the animal established in a barnyard.
12. Weaker members may die in times of food shortage, etc. as a consequence of this arrangement, but not
for any purposeful “good of the species.”
D. Territoriality (Figure 15.17)
1. A territory is a fixed area from which intruders of the same species are excluded.
2. Territorial defense occurs in insects, crustaceans, fishes, amphibians, lizards, birds and mammals.
3. Territoriality may be an alternative to dominance behavior.
4. High cost of maintaining the territory boundaries may outweigh the benefits.
5. Most energy may be expended in establishing a territory; once established, it may be easy to defend.
6. Male songbirds establish territories; the population remains stable as young assume the parent’s role.
7. Sea birds may establish a territory in a colony that is barely the size of one nest site.
8. Mammals have home ranges rather than territories, and ranges may overlap.
9. A baboon troop may switch ranges to obtain better resources.
E. Mating Systems (Figures 15.18, 15.19)
1. Behavioral ecologists classify mating systems by the extent males and females associate during
mating.
2. Monogamy is an association between one male and one female at a time.
3. Polygamy is a term that incorporates all male and female systems with more than one mate.
4. Polygyny indicates that a male mates with more than one female.
5. Polyandry is a system where a female mates with more than one male.
6. Resource defense polygyny occurs when males gain access to females by holding critical resources.
7. Female defense polygyny occurs when females aggregate and are defendable.
8. Male dominance polygyny occurs when females select mates from aggregations of males, as when a
female grouse selects a male on a communal display ground or lek.
F. Altruistic Behavior and Kin Selection (Figures 15.20, 15.21)
1. If animals behave selfishly to produce as many offspring as possible, then why do some animals help
others at risk to themselves?
2. Until the mid-1960s, it was difficult to explain altruistic behaviors.
3. Group-selection theory suggested that animals that helped others “for the good of the species” helped
the group survive, and selection was therefore at the group level.
4. Group-selection is not supported by field evidence; there is nothing to prevent a cheater who lacks the
genes from benefiting and leaving more offspring (and genes) than the altruistic risk-taker.
5. Mathematical game theory is now used to study behaviors to determine if they are evolutionarily stable
strategies or ESSs. An ESS is expected to persist over long periods of evolutionary time.
6. Kin Selection
a. In 1964, William Hamilton proposed a theory of kin selection.
b. Fitness is not just measured by an animal’s own offspring, but the increase or decrease in genes
shared in the gene pool.
c. Alleles are shared closely with parents and siblings.
d. Inclusive fitness is the relative number of an individual’s alleles that are passed on to future
generations from one’s own offspring or that of related individuals.
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Copyright © 2005 – The McGraw-Hill Companies srl
e.
15.5.
This explained the mathematics that allows eusocial insect workers to give up reproduction and
aid the queen: in a haplodiploid system, workers are 75% related to their sister queen’s offspring
compared to only 50% related to their own offspring if they were fertile and mated.
f. This places a high value on being able to recognize kin from non-kin.
Animal Communication
A. Signals
1. Through communication, one animal can influence the behavior of another.
2. Animals are limited to communication using sounds, scents, touch and movement.
3. In contrast to learned and highly variable human language, animal communication is by signals.
4. Each signal conveys one message and cannot be rearranged to construct new kinds of information.
5. The song of a cricket signals the species, sex, location and social status of the sender.
6. The cricket cannot alter his song to provide additional information.
B. Chemical Sex Attraction in Moths (Figure 15.22)
1. Virgin female silkworm moths have special scent glands to produce pheromones to attract males.
2. Adult male moths smell with their large antennae covered with thousands of sensory hair receptors.
3. The chemical attractant, bombykol, is detected and the male moth locates her.
4. Such chemical communication evolves easily since there is selection for any improved detectors.
C. Language of Honeybees (Figure 15.23)
1. Honeybees can communicate the location of food.
2. The Waggle Dance
a. This dance is used when a worker has located a rich source of pollen or nectar.
b. The dance is a figure-eight pattern on the vertical surface of a comb inside the hive.
c. The waggle run in the middle of the figure eight indicates the direction relative to the sun.
d. The tempo of the waggle is inversely related to the food’s distance from the hive.
e. If the food source is close to the hive, the forager uses a simpler round dance.
f. When food is plentiful, dancing is less common; if food is scarce, dances are intense.
D. Communication by Displays (Figure 15.24)
1. A display is a behavior that serves a communicative purpose.
2. Moth pheromones, bee dances, gull alarm calls and courtship dances are all displays.
3. The elaborate displays of the blue-footed boobies ensure that the message is understood.
4. Redundancy of display behavior also ensures that both partners are committed in courtship.
E. Communication Between Humans and Other Animals
1. Humans may have difficulty determining what sensory channel an animal is using.
2. Animal Cognition
a. Animal cognition is a general term for mental function, including perception, thinking and
memory.
b. Recent studies have focused on non-human primates and African gray parrots.
c. Researchers taught a chimpanzee to use 132 words in American Sign Language.
d. Parrots can vocalize like humans; work with the African gray parrot reveals ability to identify
shapes, colors and numbers.
e. Studies of animal cognition attempt to detect the extent some animals are capable of selfawareness and various levels of reasoning.
Lecture Enrichment
1.
2.
3.
This is a field of zoology where care with terminology is very important, and there are far more definitions provided
in this chapter than in any other chapter. It is critical to avoid “anthropomorphizing,” using terms that place human
thoughts into the minds of animals, for animals do not mentally verbalize.
Animal behavior is a fabulously interesting part of zoology, but only if students can see the behaviors that are often
rare or seasonal or hard to view in nature. Therefore, use of videos is particularly important in this section to
illustrate the often complex behaviors described.
Nearly seventy years ago and well before William Hamilton, J.B.S. Haldane [of the Oparin-Haldane hypothesis]
wrote a brief and very readable article describing the limited benefits of a gene for altruism. His example is useful
in classes to simplify the complex mathematics. If a gene promoted jumping overboard to rescue a person, and the
risk of drowning from such an action was 1-in-10, simple genetics allows us to calculate that the gene will increase
in frequency if we only save our own children, brothers and sisters (who share one-half of our genes) or our
grandchildren and near distant relatives who share one-fourth or one-eighth our genes. Consequently, if we save
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4.
5.
more distant relatives or strangers, the gene would fade from existence because it now has a higher chance of being
lost than saved–the chance of dying exceeds the chance of saving the gene carriers.
It is very important not to exaggerate the reports of animal use of language. A critique of such research is available
in Joel Wallman’s Aping Language, Cambridge University Press, 1993.
Likewise, students may confuse evidence of animal self-recognition to human self-awareness. To distinguish these,
an instructor can use examples from D.L. Cheney and R.M. Seyfarth, How Monkeys See the World, Univ. Chicago
Press, 1990.
Commentary/Lesson Plan
Background:
Misconceptions:
Schedule:
HOUR 1 15.1. Science of Animal Behavior
A. Ethology
15.2. Describing Behavior: Principles of
Classical Ethology
A. Early Work
15.3. Control of Behavior
A. Innate Behavior
B. Genetics of Behavior
C. Learning and the Diversity of
Behavior
15.4. Social Behavior
A. Definitions
B. Advantages of Sociality
C. Aggression and Dominance
D. Territoriality
E. Mating Systems
F. Altruistic Behavior and Kin
Selection
15.5. Animal Communication
A. Signals
B. Chemical Sex Attraction in Moths
C. Language of Honeybees
D. Communication by Displays
E. Communication Between Humans
and Other Animals
ADVANCED CLASS QUESTIONS:
1. What evidence would you seek to determine if left or right handedness was genetic or learned? With humans, we do
not conduct breeding experiments but must work with natural assortments of individuals. If handedness was a
Mendelian trait with one handedness dominant and the other recessive, what combinations would disprove a simple
hereditary model?
2. In a most general sense, as we move from protozoans to mammals there is an increase in the repertoire of learned
behaviors. Why?
Twelfth Edition Changes: Some new information has been added to this chapter:
1.
2.
3.
4.
5.
Questions of ultimate causation are answered using comparative methodology applying phylogenetic analysis to
understand evolutionary changes in behavior and their associated morpholocal and environmental contexts.
Much of the work by comparative psychologists and ethologists can be found under the discipline of behavioral
ecology.
Behavioral ecologists often focus on how individuals are expected to behave to maximize their reproductive
success.
There is an extensive discussion on reciprocal altruism and new information concerning evolutionary stable
strategy (ESS).
Phylogenetic studies have been important for testing hypotheses of the evolution of mating behavioral and
morphological characters by sexual selection.
Source Materials
[Bold = recommended; vendor abbreviations are provided in Appendix 1]
The Aggressive Impulse (EBE), 24-min. video
Analysis of Behavior (IM) 40-min. video
Animal Behavior (IM), 29-min. video
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Animal Behavior Data Simulation (OAK), MS-DOS and Mac
Animal Behavior: The Mechanism of Imprinting (PHO), 15-min. video
Animal Defenses (JLM), slides (20)
Animal Senses (IM), 30-min. video
Baboon Behavior (UC), 31-min. video
Baboon Social Organization (UC), 17-min. video
Behavior and the Protein Record (FH), 20-min. video
Bird Brain: The Mystery of Bird Navigation (T/L), 27-min. video
Breeding Behavior of Tropical Pelagic Birds (UC), 18-min. video
Chemical Communication (BSCS Classic Inquiry) (MDA), videodisc
Community Dynamics (EME, PLP), Apple, MS-DOS
Courting (FH), 27-min. video
Deception in the Animal Kingdom (JLM), slides (20)
Feeding Behavior of Aquatic Carnivorous Turtles (UC), 13-min. video
Feeding Behavior of Burton's Pygopodid (UC), 10-min. video
Feeding Behavior in Hydra (BSCS Classic Inquiry) (MDA), videodisc
Feeding and Defense in Arachnids (UC), 11-min. video
Feeding and Swimming Behavior of the Antarctic Krill (UC), 10-min. video
Flights of Fancy: Insect Reproductive Strategies (IM), 58-min. video
Food Handling in Kangaroo Rats (UC), 10-min. video
The Fruit Fly: A Look at Behavior Biology (CRM), 21-min., video
Function of Beauty in Nature; Konrad Lorenz—Science of Animal Behavior (NG), 14-min. each
Hunting Behavior of the Aplomado Falcon (UC), 14-min. video
Imprinting (BSCS Classic Inquiry) (MDA), videodisc
Jane Goodall (CBSC), 28-min. video
Life's Clocks (JLM), 27-min. video
Mating Behavior in the Cockroach (BSCS Classic Inquiry) (MDA), videodisc
Mechanics of Flight in Flying Foxes (UC), 8-min. video
Metabolism and Activity of Lizards (UC), 12-min. video
Miss Goodall and the Lions of Serengeti (FI), 52-min. video
Mysteries of Nature (FH), Mac, Win CD
NATURE: Bower Bird Blues (WNET), 1-hr. video
NATURE: Conversation With Koko (WNET), 1-hr. video
NATURE: Extraordinary Cats (WNET), 1-hr. video
NATURE: Extraordinary Dogs (WNET), 1-hr. video
NATURE: Inside the Animal Mind (WNET), 3-hr. video
NATURE: Jane Goodall’s Wild Chimpanzees (WNET), 1-hr. video
NATURE: The Joy of Pigs (WNET), 1-hr. video
NATURE: Mans Best Friend (WNET), 1-hr. video
NATURE: Monkey in the Mirror (WNET), 1-hr. video
NATURE: Mozu The Snow Monkey (WNET), 1-hr. video
NATURE: Nature of Sex (WNET), 6-hr. video
NATURE: Parrots Look Who’s Talking (WNET), 1-hr. video
NATURE: Sea Otter Story–Warm Hearts and Cold Water (WNET), 1-hr. video
Nesting Behavior of the Egyptian Plover (UC), 14-min. video
NOVA: Animal Imposters (JLM) (NEB), 60-min. video
NOVA: Mystery of Animal Pathfinders (JLM) (NEB) (PHO), 60-min. video
NOVA: Private Lives of Dolphins (NEB), 60-min. video
Ourselves and Other Animals (FH), 12-part series of 27-min. videos
Pavlov: The Conditioned Reflex (FH), 25-min. video
Predatory Behavior of Snakes (UC), 16-min. video
Predatory Behavior of the Grasshopper Mouse (UC), 10-min. video
Prey Capture by Terrestrial Toads and Frogs (UC), 11-min. video
Prey Detection in the Rattlesnake (BSCS Classic Inquiry) (MDA), videodisc
Private Life of the Herring Gull (T/L), 26-min. video
Questions About Behavior (IM) 25-min. video
Recognizing Gender Differences (FH), 24-min. video
340
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Regulation of Social Organization (FH), 27-min. video
Reproduction: Coming Together (FH), 26-min. video
Reproduction and Social Behavior of Belding's Ground Squirrel (UC), 18-min. video
Research in Animal Behavior (H&R), 19-min. video
The Rituals of Courtship (FH), 25-min. video
Sociobiology: The Human Animal (T/L), 23-min. video
Social Behavior in Chickens (BSCS Classic Inquiry) (MDA), videodisc
Social Primates (IM) 38-min. video
Societies (FH), 27-min. video
Stimulus Response in Animals (FH), 33-min. video
Thinking Animals (FH), 27-min. video
Ultrascience: What Do Animals Feel? (AVP), 30-min. video
Ultrascience II: Mosquito Wars (AVP), 30-min. video
Ultrascience II: Talk to the Animals (AVP), 30-min. video
WARD's Animal Behavior: Habitat Selection (WARDS), Mac, Win CD
Washoe: Apes and Sign Language (FH), 52-min. video
Why Do Birds Sing? (T/L), 27-min. video
341
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Copyright © 2005 – The McGraw-Hill Companies srl
CHAPTER
16 THE BIOSPHERE AND ANIMAL DISTRIBUTION
CHAPTER OUTLINE
16.1.
16.2.
Earth Environment (Figure 16.1)
A. Overview
1. Water has physical properties critical to life on earth.
2. The steady supply of sunlight maintains a suitable range of temperatures for life metabolism.
3. Living matter requires a supply of major and minor elements available on earth.
4. The earth’s gravity is strong enough to hold an extensive gaseous atmosphere.
5. The environment is modified by organisms; organisms are adapted by evolution to the
environment.
6. The earth is an open system with a continuous supply of energy.
7. Building materials for life come from producers and are cycled through consumers.
8. Life is part of a cycle of life-death-decay-recycling.
9. The primitive earth of 4.5 billion years ago had a reducing atmosphere of ammonia, methane and
water and was fit for pre-biotic synthesis of early living forms.
10. This early atmosphere would be fatal to today’s organisms.
11. The appearance of free oxygen in the atmosphere is an example of the reciprocity of life and the
earth.
12. Living organisms produce changes in their environment and must adapt and evolve.
Distribution of Life on Earth (Figures 16.2, 16.3)
A. Biosphere and Its Subdivisions
1. The biosphere is the thin outer layer of the earth capable of supporting life.
2. It is a global system including all life on earth and the physical environments where organisms
exist.
3. The lithosphere is the rocky material of the earth’s shell and is the source of all mineral elements.
4. The hydrosphere is the water on the earth’s surface; it extends into the lithosphere and
atmosphere.
a. The global hydrological cycle involves evaporation, precipitation and runoff.
b. Five-sixths of the evaporation is from the ocean, and more evaporates from the ocean than
returns.
c. This difference is rainfall that supports life on land.
5. Atmosphere extends up 3500 kilometers above the earth surface; life is confined to the lower 8-15
km.
a. A layer of oxygen-ozone screens ultraviolet light at between 20 and 25 km altitude.
b. Gases present in the atmosphere are nitrogen (78%), oxygen (21%), argon (0.93%), carbon
dioxide (0.03%) and varying amounts of water vapor.
c. Atmospheric oxygen originates nearly completely from photosynthesis.
d. The present level of oxygen was reached by the mid-Paleozoic about 400 billion years ago.
e. The earth’s oxygen surplus will remain due to its vast supply and ongoing photosynthesis.
f. Current rapid input of carbon dioxide from burning fossil fuels may significantly affect the
earth.
g. Much of the sun’s energy is absorbed and re-radiated as heat energy.
h. The greenhouse effect describes the measurable trapping of this heat in the atmosphere.
i. Carbon dioxide is a greenhouse gas and adds to this effect.
j. Accumulation of carbon dioxide could lead to an increase in the temperature of the biosphere.
B. Terrestrial Environments: Biomes (Figures 16.4-16.6)
1. A biome is a major biotic unit with characteristic and easily recognized plant life.
2. Plant distribution is easier to map, but plant formations support characteristic animal life.
3. Biomes are distinctive but the boundaries are not; communities grade into one another.
4. A gradient from forest to woodlands to prairies forms an ecocline.
5. Biomes nevertheless have distinctive dominant plants and animals.
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The Climate Machine
a. Global variation in climate arises from uneven heating of each region due to the solar
radiation.
b. More sunlight directly hits the equator and therefore more heat is absorbed.
c. Warmed air is lighter and rises and moves toward the poles; it is replaced by cooler air
moving along the surface from the poles.
d. Air circulation in each hemisphere is broken into three latitudinal zones or cells.
e. Hot moist air from the equator cools as it rises, condensing and saturating the rain forests.
f. Dry air sinks at 20-30o latitude; it sinks in regions where there are subtropical belts of deserts.
g. The Coriolis Effect of the earth’s rotation also deflects air circulation.
7. Temperate Deciduous Forest
a. We see these forests well developed in eastern North America.
b. Deciduous, broad-leafed trees such as oak, maple and beech shed their leaves in winter.
c. Deciduous trees are adapted for low-energy levels from the sun and for freezing winter
conditions.
d. In the summer, the closed canopy creates a deep shade underneath.
e. Therefore, understory plants grow rapidly in spring or fall.
f. Rain falls throughout the year and climate is relatively wet.
g. Animal communities are adapted to seasonal changes; some migrate and some hibernate.
8. Coniferous Forest (Figure 16.7)
a. Coniferous forests form a broad, continuous belt across Canada and Alaska and south through
the Rocky Mountains into Mexico.
b. This biome also continues across northern Eurasia.
c. It is dominated by evergreens: pines, fir, spruce and cedar.
d. These plants are adapted to withstand freezing and survive with short summer growing
seasons.
e. The trees conical shape shed snow.
f. The northernmost edge is boreal forest, often called taiga.
g. Mean annual precipitation is less than 100 cm (40 inches) and temperatures are fairly cold.
h. Mammals include deer, moose, elk, snowshoe hares, many rodents, foxes, wolverines, lynxes,
weasels, martins and bears.
i. Animals must be adapted physiologically or behaviorally for long, cold and snowy winters.
j. Birds are adapted to the forest resources.
k. Many mosquitoes and flies are adapted to feed on the blood of the large mammals.
l. Southern coniferous forests lack northern mammals, but have snakes, lizards and amphibians.
9. Tropical Forest (Figure 16.8)
a. The worldwide equatorial belt of tropical forests has high rainfall and constant temperatures.
b. This nurtures luxurious, uninterrupted growth that is at a maximum in rain forests.
c. Compared to deciduous forests with a few dominant tree species, the tropical forest may have
up to a thousand species and none are dominant.
d. Tropical forests are often stratified into six to eight feeding strata.
e. Insectivorous birds and bats fly the air above the canopy.
f. Middle zones have tree species such as monkeys and tree sloths, birds and amphibians.
g. Climbing animals range along the trunks.
h. Large mammals that are unable to climb forage on the forest floor.
i. A large community of carnivores and herbivores scavenges in the litter and on trunks for
food.
j. Food webs are intricate and difficult to unravel.
k. Litter is thin and the soil is an impoverished laterite; most of the biomass is in the forest
above.
10. Grassland (Figure 16.9)
a. North American prairie is one of the most extensive grasslands in the world.
b. Much prairie has been transformed into the most productive agricultural region in the world.
c. In grazing lands, nearly all native grasses have been replaced by exotic species.
d. The bison was the dominant herbivore, but jackrabbits, antelope, and prairie dogs remain.
6.
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e.
f.
Mammalian predators include coyotes and the now uncommon ferrets, badgers, and cougar.
Annual rainfall is more than in deserts, less than deciduous forests, at 40-80 cm (16-31
inches).
11. Tundra (Figure 16.10)
a. Tundra is a severe cold biome in treeless Arctic regions or high mountaintops.
b. Plant life is restricted to a short growing season of about 60 days.
c. Soil remains frozen most of the year; annual precipitation is usually less than 25 cm (10
inches).
d. Dwarf woody vegetation, lichens, grasses, and sedges predominate.
e. Arctic animals include lemming, caribou, musk ox, arctic fox, ptarmigan and migratory birds.
12. Desert
a. Deserts receive less than 25 cm (10 inches) of rainfall a year.
b. Desert plants have reduced foliage, drought-resistant seeds and adaptations to conserve water.
c. Large desert animals are adapted for keeping cool and conserving water.
d. Smaller animals often live in burrows or are nocturnal.
e. Desert mammals include mule deer, jackrabbit, peccary, kangaroo rat and ground squirrel.
f. Desert birds include the roadrunner, cactus wren, turkey vulture and burrowing owl.
g. Reptiles are numerous and many insects and arachnids are also desert adapted.
C. Aquatic Environments
1. Inland Waters
a. Freshwater constitutes only 2.5% of the water in the world.
b. Most is stored in ice caps or underground aquifers leaving only 0.01% as freshwater habitat.
c. Yet a quarter of the world’s vertebrates and half of its fishes live in freshwater.
d. Lotic waters are flowing and have high oxygen content.
e. Lentic water is standing water and has less dissolved oxygen.
f. A large number of animals live on the bottom as benthic organisms.
g. Swimming freshwater organisms found in lakes and larger ponds are nekton.
h. Small floating plants and animals are plankton.
i. Lakes and ponds are generally short-lived since they eventually fill up with sediment.
j. Human pollution includes the inflow of nitrates and phosphates that cause huge blooms of
algae.
2. Oceans (Figures 16.11, 16.12)
a. Oceans easily represent the largest portion of the earth’s biosphere.
b. The marine world is relatively uniform, compared to land.
c. Over 200,000 species live in oceans and 98% are benthic and live on the seabed.
d. Only 2% are pelagic, swimming freely in the ocean.
e. Of the benthic forms, most live in intertidal or shallow regions; less than 1% live in deep
ocean.
f. The most productive areas are where upwelling currents bring nutrients to the sunlit photic
zone.
g. With a few exceptions, life below the photic zone lives on the “rain” of organic matter from
above.
h. The littoral, or intertidal zone, where sea and land meet is the richest and harshest
environment.
i. Intertidal zones provide the most diverse habitats.
j. Below the littoral is the rich sublittoral or subtidal zone that is always submerged.
k. An estuary is a transition zone where freshwater mixes with seawater; it is nutrient-rich.
l. A neritic or shallow water zone extends to the end of the continental shelf; nutrients are
delivered by rivers and upwellings and algal growth is prolific.
m. Upwellings are restricted to small areas; many productive fisheries are centered on
upwellings.
n. The vast open ocean constitutes the pelagic realm.
o. Except in upwellings, organisms that die here sink to the bottom.
p. The polar seas combine upwellings with high oxygen content; they support enormous
populations of krill that feed on phytoplankton.
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16.3.
q. The surface is the epipelagic layer.
r. The mesopelagic is the “twilight zone” where dim light supports a community of animals.
s. In perpetual darkness are the bathypelagic, abyssopelagic and hadopelagic zones.
t. Deep-sea forms are limited by the portion of organic debris that rains from above.
u. Most deep ocean bottom dwellers are deposit feeders with slow growth and long lives.
Animal Distribution (Zoogeography)
A. Geological History
1. Zoogeography tries to understand why animals are distributed where they are and how they
disperse.
2. Most animals have a limited geographic range; humans and a few other animals can live
anywhere.
3. Barriers can prevent a population from moving from one region to another identical habitat
elsewhere.
4. Study of fossils often shows that animals occurred in areas where they are now absent.
5. For instance, ancestors of camels originated in North America and spread across Alaska to Eurasia
and Africa; their descendants occur as true camels in Africa and llamas in South America.
6. It is important to know the fossil history of the animal species to understand its present range.
7. Geological changes and changes in climate are also important in understanding zoogeography.
B. Disjunct Distributions (Figure 16.13)
1. Disjunct distributions occur when closely related species live in widely separated areas.
2. There are two possible explanations for disjunct distributions.
a. Dispersal is the simple movement of a population from one locale to another and the
intervening territory is not suited for long-term colonization.
b. A second scenario has a widely distributed population broken into separate populations due to
a vicariance event such as climate change, habitat fragmentation or movement of landmasses.
C. Distribution by Dispersal (Figure 16.14)
1. Dispersal can involve emigration away from a home region and/or immigration into another
region.
2. Dispersal is one-way movement, not to be confused with seasonal migrations.
3. Animals can disperse under their own power, or passively disperse by wind, floating, etc.
4. Animals have high reproductive rates and this provides continuous pressure to move into new
ranges.
5. The retreat of Pleistocene glaciers left favorable habitats for animals that could disperse into them.
6. In tracing back the origin of animals, as in the case of flightless ratite birds on isolated islands, it is
necessary to locate the center of origin of the species.
7. Long-distance dispersal and vicariance events are both used to explain current animal
distributions.
D. Distribution by Vicariance
1. The study of fragmentation of biotas is called vicariance biogeography.
2. At the species level, “vicariance” can be used as a synonym of “allopatry” or separation of
populations.
3. Since speciation is likely to occur when populations are geographically isolated, an analysis of the
relatedness of modern species should match up with geographically isolating or vicariant events.
4. A branching pattern for species that matches the pattern of vicariant events, forms a general area
cladogram that depicts the history of fragmentation of the geographic areas studied.
5. The remaining branch may be a case of dispersal; of a cladogram for a taxon, that explains all but
one branch by vicariant events.
E. Continental Drift Theory
1. Alfred Wegener proposed continental drift theory in 1912; it was ignored until a new theory of
plate tectonics provided a mechanism.
2. The earth’s surface is composed of 6 to 10 rocky plates that shift on a malleable underlying layer.
3. The earth’s continents have been drifting since the breakup of a single landmass called Pangaea.
4. Pangaea broke apart 200 million years ago, forming a northern Laurasia and a southern
Gondwana.
5. About 135 million years ago, these supercontinents further fragmented and drifted apart.
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6.
7.
This theory is now supported by the fit of continents, paleomagnetic surveys, seismographic
studies, mid-ocean ridges where the ocean bottoms spread, and much biological data.
The Case of Marsupial Evolution
a. Marsupials appeared about 100 million years ago in South America.
b. They spread through Antarctica and Australia that were at that time joined together.
c. Marsupials encountered placental mammals in North America and could not compete, and
became extinct; the modern opossums are recent arrivals from South America.
d. The placental expanded into South America, but the marsupials were well established there.
e. About 50 million years ago, Australia drifted apart from Antarctica and remained in isolation
with only marsupials to diversify on the continent.
f. Temporary land bridges have also occurred; the bridge across the Bering Strait was an
important corridor for placentals to enter North America.
g. The land bridge from North to South America was absent from 50 million years ago to 3
million years ago, but accounts for dramatic changes in animal life after the bridge was
reestablished.
Lecture Enrichment
1.
2.
3.
4.
5.
6.
We are so used to moving laterally on the surface of the earth that we do not appreciate how limited we are “upand-down.” Probably some students travel to class each day a distance of 15 or 20 miles; they cannot travel
half that distance upward or down in the ocean without special protective gear, as they can understand if they
have been aboard a jetliner. The biosphere is relatively very thin.
In discussion of the organism-environment relationship, students may bring up the Gaia hypothesis that asserts
that the earth is self-healing and actively maintains a wide array of physical conditions within habitable limits.
Gaia proponents vary from bona-fide researchers making limited claims, to New Age mother-earth
philosophers. An instructor should keep discussion centered on biology and geology.
One explanation for why tropical forests lack dominant trees is provided by work by Dan Jantzen. He observed
that there is no winter to knock down seed predators, and clusters of dominant trees would build up seed
predators that would consume 100% of the seeds. A species that has members spaced far apart makes it
difficult for seed predators to locate and build up populations. His experiments in Costa Rica show decimation
of seeds when he concentrates a plant in one area.
The ecocline should not be considered an unfavorable habitat unsuitable for residents of biomes to either side.
There are usually relict communities or islands of “forests” within grasslands and grasslands within forests, etc.
that provide “homes” for animals out of their main range. An ecocline often presents a unique and often more
diverse mix of animals not found deep within either biome.
Not all animals adjusted to natural and wild biomes will be adversely affected by human settlement. The whitetailed deer and the coyote are two examples of wild animals that have not reduced numbers, and encroach on
human activity.
The study of biogeography is closely allied with systematics and taxonomy described in Chapter 10. In
describing new species and establishing genera, etc., the systematist often tries to work out the center or origin
and determine where the group was originally endemic, sometimes with the help of fossil evidence if it is
available.
Commentary/Lesson Plan
Background: Students that have diving experience can relate how we are limited to several hundred feet diving
depth unless protected in a pressure bell. Thanks to nature and underwater documentaries on television, many of
these biomes and realms will be familiar to students in travelogue fashion, and most students have probably moved
among several during vacations, etc.
Misconceptions: On land, abundant water means luxurious growth; therefore, it is difficult for some students to
imagine that the open ocean is essentially a “desert” in terms of abundance of organisms.
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Schedule:
HOUR 1 16.1. Earth Environment
A. Overview
16.2. Distribution of Life on Earth
A. Biosphere and Its Subdivisions
B. Terrestrial Environments: Biomes
C. Aquatic Environments
16.3. Animal Distribution (Zoogeography)
A. Geological History
B. Disjunct Distributions
C. Distribution by Dispersal
D. Distribution by Vicariance
E. Continental Drift Theory
ADVANCED CLASS QUESTIONS:
1. Why do the distributions of animals not exactly match the vegetation zones? Why does the distribution of a
plant species not always match the vegetation zone to which it is characteristic?
2. The Saharan Desert is just north of the equator; why does it not have lush rain forests as occur in the Amazon?
3. Fossils of ferns and other warm climate organisms have been found in the rocks of Antarctica. Explain this.
Twelfth Edition Changes: Only minor changes have been made to this chapter:
1.
There is a new box describing the contributions of Alfred Russel Wallace to modern historical biogeography.
Source Materials
[Bold = recommended; vendor abbreviations are provided in Appendix 1]
Adaptation to Site (FH), 28-min. video
America's Rainforest: A Disappearing Glory (FH), 35-min. video
Antarctica on the Edge: Impending Ecological Doom (FH), 52-min. video
Applied Biology/Chemistry: Water (FH), Mac, Win CD
Applied Biology/Chemistry: Natural Resources (FH), Mac, Win CD
Aquaculture (FH), 26-min. video
The Balance of Nature (FH), 28-min. video
Basic Ecology (IM), 29-min. video
Bioethics Forums (VDISC) laserdisc
Bioethics Forums: Development and Biodiversity (CAM), Mac, Win CD
Biomes (CBSC), Mac, MS-DOS CD
Biomes (IM), MS-DOS and Mac CD
Biomes and Food Webs (PLP), Mac, MS-DOS
Biomes and Natural Cycles (Q), Mac, Win CD
Biosphere: Life in a Glass Bubble (FH), 30-min. video
The Biosphere (HH), 42-min. video
Casualties of the Wild: Animal Recovery (FH), 28-min. video
Comprehensive Review in Biology: Ecology (Q), Mac, Win
The Commons: An Environmental Dilemma (K-H), Mac, Win CD
Decisions, Decisions: The Environment (CSG), Mac
Earthbeat: Global Warming (IM), 25-min. video
Ecodisc (WARDS), Mac CD
Ecology (NEB) (PLP), Mac, MS-DOS
Ecology CD-ROM Set (SKBL), Mac, Win CD
Ecology: Interactions and Environments (PHO), filmstrip
Ecology and the Environment: Galapagos, Mauritania, Madagascar (FH), 33-min. video
Ecology of North American Grasslands (JLM), slides (40)
Ecology Sampling Methods (IM), 32-min. video
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Ecology: Wanted Alive! (AIMS), 10-min. video, laserdisc
EcoSim and EcoStat (SciT) (TS), MS-DOS
EcoSim: An Ecological Simulation Program (TS), MS-DOS
Ecosystem, Parts 1-3 (ei), video
An Ecosystem: A Struggle for Survival (NG), 22-min.
Ecosystems (HH) (IM) (JLM) (SKBL), 31-min. video
Ecosystems and the Biosphere (IM), 30-min. video
El Nino: Disaster on the Wind (FH), 35-min. video
The Environment (FH), 23-min. video
Environmental Ethics (SLVP), 40-min. video
Environmental Problems (JLM), slides (40)
The Estrogen Effect: Assault on the Male (FH), 51-min. video
Exploration of the Earth's Marine and Freshwater Systems (WARDS), Mac, Win CD
Focus on Environment CD-ROM (CBSC) (WARDS), Mac, MS-DOS CD
Focus on Environment 4-Part Series (PLP), Mac, MS-DOS
4,000 Meters Under the Sea (FH), 28-min. video
Future of Energy Gases (JLM), 30-min. video
Feast or Famine (FH), 27-min. video
Focus on Environment (WARDS), Mac, Win CD
Food for Tomorrow: Critical Issues in Global Agriculture (SLVP), 30-min. video
Food Policy in the Dynamics of Global Agriculture (SLVP), 23-min. video
Fragile Ecosystems (FH), 23-min. video
Future of Energy Gases (JLM), 30-min. video
The Gaia Hypothesis (FH), 25-min. video
The Global Gardener (SLVP), 30-min. video
Global Trends Presentation Set (WRI), 50 slides or transparencies
Global Warming--Future Quest (HH), 31-min. video
The Great Barrier Reef (FH), 60-min. video
Great Lakes Alive: Clear Water, Cloudy Future (FH), 56-min. video
Great Lakes Alive: To The Last Drop (FH), 60-min. video
Great Lakes Alive: Restoring the Balance (FH), 60-min. video
The Greenhouse Effect (IM) (NEB), 17-min. video
The Greenhouse Effect and Global Climate: Jessica Tuchman Mathews (FH), 30-min. video
Health and the Environment: Epidemics and the Environment (FH), 29-min. video
Health and the Environment: Dealing with Solid Waste (FH), 30-min. video
The Heat is On: The Effects of Global Warming (FH), 26-min. video
The History of the Earth: Over the Eons (AIMS), Mac, Win CD, 30-min. video
Hole in the Sky: The Ozone Layer (FH), 52-min. video
Hothouse Planet (EME, PLP), Mac, MS-DOS, Mac
How the Biosphere Was Born (HH), 15-min. video
Introduction to Ecology (JLM), slide set (20)
Introduction to General Biology: Ecology (Q), Mac, DOS
Investigating Lake Iluka (Q), Mac, Win CD
Is the Weather Changing (PHO), 16-min. video
Is There Global Warming? (HH) (JLM), 15-min. video
Land Pollution (ei), slides
Last Chance to See (Q), Mac or MS-DOS CD
The Last Drop: Is The World Running Out of Water? (FH), 51-min. video
Learning About Our Environment (Q) (WARDS), Mac, Win CD
Learning to Live in a World of Plenty (HH), 21-min. video
Learning to Live in a World of Scarcity (HH), 27-min. video
The Living Planet (AVP) (JLM), 12 60-min. videos
Lost Worlds, Vanished Lives (AVP), 4 40-min. videos
Man and the Biosphere: Life in Arid and Semi-Arid Lands (FH), 28-min. video
Man and the Biosphere: The Desert as Laboratory (FH), 28-min. video
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Man and the Biosphere: Life at the Top (FH), 28-min. video
Man and the Biosphere: Equilibrium in a Mountain Habitat (FH), 28-min. video
Man and the Biosphere: Coastlines (FH), 28-min. video
Man and the Biosphere: Ecology of the Coral Reef (FH), 28-min. video
Man and the Biosphere: Urban Ecology (FH), 24-min. video
Man and the Biosphere: Toward a Livable City (FH), 28-min. video
The Miracle of Agriculture: Growing a Sustainable Future (SLVP), 45-min. video
The Miracle Planet (AVP), 6 60-min. videos
Modeling Animal Populations: Blue Haven (FH), 25-min. video
Mount St. Helens: Out of the Ash (FH), 50-min. video
Natural Resources–Future Quest (HH), 33-min. video
Natural Resources (Q), Mac, Win CD
NATURE: Forest in the Sea (WNET), 1-hr. video
NATURE: Iceland–Fire and Ice (WNET), 1-hr. video
NATURE: Land of the Eagle (WNET), 4-hr. video
NATURE: Seasons in the Sea (WNET), 1-hr. video
NATURE: Wild Shores of Patagonia (WNET), 1-hr. video
NATURE: Realm of the Russian Bear (WNET), 6-hr. video
NATURE: Gremlins–Faces in the Forest (WNET), 1-hr. video
NATURE: Life at the Edge of the Sea (WNET), 1-hr. video
NATURE: Secret World of Sharks and Rays (WNET), 1-hr. video
NATURE: American Buffalo–Spirit of a Nation (WNET), 1-hr. video
NATURE: Humpback Whales (WNET), 1-hr. video
NATURE: Spirit of the Sound (WNET), 1-hr. video
NATURE: The Emerald Isle (WNET), 1-hr. video
NATURE: Secrets of an African Jungle (WNET), 1-hr. video
NATURE: Pantanal–The Great Prairie (WNET), 1-hr. video
NATURE: Treasure of the Andes (WNET), 1-hr. video
No Easy Answers (PHO), 14-min. video
North American Ecosystems (Q), Mac, Win CD
NOVA: Adrift on the Gulf Stream (NEB) (WGBH), 60-min. video
NOVA: Acid Rain: New Bad News (UM), 60-min. video
NOVA: City of Coral (NEB) (WGBH), 60-min. video
NOVA: Cracking the Ice Age (WGBH), 60-min. video
NOVA: Dying to Breathe (WGBH), 60-min. video
NOVA: The Endangered Earth: The Politics of Acid Rain (UM)
NOVA: Journey to the Sacred Sea (NEB) (WGBH), 60-min. video
NOVA: Haunted Cry of a Long Gone Bird (WGBH), 60-min. video
NOVA: The Hole in the Sky (UM), 60-min. video
NOVA: Saddam's War on Wildlife (UM), 60-min. video
NOVA: Warnings from the Ice (WGBH), 60-min. video
NOVA: The Water Crisis (UM), 60-min. video
Ocean Resources (FH), 23-min. video
Oceanography (FH), 23-min. video
Oceanus: The Marine Environment (PLP), 30 30-min. videos
Organic Cleanup: Microbes and Pollution (FH), 28-min. video
Our Fragile World (FH), 4-part series of 15-min. videos
Ozone: Protecting the Invisible Shield (NGS), 25-min. video
Planet Earth (CPB), 7 one-hour videos
Pollution Control (PLP), Mac, MS-DOS
Pollution Simulator (ei), MS-DOS
Pollution: World at Risk (NGS), 25-min. video
Powers of Ten (PYR), 10-min. video
Principles of Ecology (FH), 23-min. video
Race to Save the Planet (IM) (JLM) (CPB), 10 1-hr. videos
Fondamenti di zoologia
Cleveland P. Hickman, Jr., Larry S. Roberts, Allan Larson, Helen I'Anson
Copyright © 2005 – The McGraw-Hill Companies srl
Rainforest Remedy (FH), 31-min. video
Rainforest: The Puzzle of Biodiversity (FH), 24-min. video
Recycle (AIMS), Mac, Win CD, 16-min. video, laserdisc
Recycling: The Endless Circle (NGS), 25-min. video
Reduce (AIMS), Mac, Win CD, 14-min. video, laserdisc
The Redwoods (PHO), 21-min. video
Reuse (AIMS), Mac, Win CD, 13-min. video, laserdisc
The Roots of Wildlife Conservation (FH), 43-min. video
A Sand County Almanac (PHO), 16-min. video
Saving the Atmosphere (FH), 15-min. video
Science and Human Values (EME), 24-min. video
The Search for Clean Air (FH), 57-min. video
Secrets of the Bay (UC), 28-min. video
Secret of the Rain Forest: The Tree Canopy (FH), 51-min. video
The Sky's the Limit (UC), 56-min. video
Sustainable Agriculture (SLVP), 30-min. video
Sustainable Environments (SLVP), 33-min. video 3d Atlas (WRI), CD in Mac, Win
Through Fish Eyes: A Close-Up Look at Water Pollution (FH), 30-min. video
The Tragedy of the Commons (PHO), 23-min. video
Ultrascience: Fast Frozen Future (AVP), 30-min. video
Volcanoes and the Atmosphere (FH), 25-min. video
Urban Ecology (FH), 24-min. video
WARD’S Exploring Environmental Science Topics CD-ROM (WARDS), Mac, Win CD
WARD's Exploring Environmental Science: Water Quality Testing and Analysis (WARDS), Win CD
Water (Q), Mac, Win CD
The Water Cycle (WARDS), 20 slides
Water: A Precious Resource (NGS), 40-min. video
Waterworld (FH), 60-min. video
The Wetlands Explorer (NEB), Mac, Win CD
What Is Ecology? (CBSC) (EBE), 21-min. video
When the Rivers Run Dry (UC), 29-min. video
Wild America: Who Needs It? (PHO), 20-min. video
A World Alive (JLM), 25-min. video
World Habitats (FH), Win CD
The World of Natural Science: Ecology (FH), 15-min. video
The World of Natural Science: Land Ecosystems (FH), 14-min. video
The World of Natural Science: Aquatic Ecosystems (FH), 15-min. video
The World of Natural Science: Environmental Pollution (FH), 15-min. video
The World of Natural Science: Forestry and Mining (FH), 15-min. video
The World of Natural Science: Forest Management (FH), 15-min. video
The World's Weather (FH), Mac, Win CD
Yellowstone Aflame (JLM), 30-min. video