THREE DOMAINS NOTES
LEVELS OF ORGANIZATION
Cells – Tissue – Organ – Organ System - Organism – Population – Community – Ecosystem
FREE ENERGY AND ORGANISMS
A. Living systems require free energy and matter to maintain, grow, and reproduce
B. Energy deficiencies are detrimental to individual organisms and can also cause disruptions at the
population and ecosystem level
C. Heterotroph and Autotroph – Words that describe the two possible ways that organisms capture
and store free energy for use in biological processes; how cells can meet their energy needs
D. Heterotrophs
1. These organisms must "take in" nutrition
2.they capture free energy that is present in carbon compounds produced by other organisms
3. includes all animals, all fungi, and many protists and bacteria
E. Autotrophs
1. these organisms capture free energy from physical sources (simple inorganic substances)
in the environment and then make their own food (energy-rich organic molecule glucose)
2. Two different kinds of autotrophs
a. Photosynthetic autotrophs
1) organisms that capture free energy present in sunlight and use it for their
synthesis reactions to produce glucose (during photosynthesis)
2) includes plants and several types of protists and bacteria
b. Chemosynthetic autotrophs
1) organisms that capture free energy from small inorganic molecules (such
as sulfur or methane) present in their environment (this process can
occur in the absence of oxygen)
2) includes certain groups of bacteria
F. Metabolism = the chemical processes that occur within a living organism in order to maintain
life; these chemical processes use the food available to the organism and provide energy to
the organism
F. Metabolic rate = the speed at which an organism’s cell perform the reactions that keep it alive;
the rate at which metabolism occurs in an organism
a. There is a relationship between metabolic rate per unit body mass and the size of
multicellular organisms
b. Generally, the smaller the organism, the higher the metabolic rate
G. If an organism acquires more free energy than the amount that is necessary to survive, it puts that
extra free energy into storage or growth
H. If an organism doesn’t acquire sufficient free energy that is necessary to survive (its expenditure
is greater than what it acquires), the result is a loss of mass, and ultimately, the death of the
organism
THERMOREGULATION - Strategies for regulation of body temperature & metabolism
I. Ectothermy – when organisms can only use external thermal energy to help regulate and maintain body
temperature
A. Behavioral, physiological, or anatomical adaptations that increase an animal's ability to survive
in a certain environment
1. hibernation
2. hair, feathers, blubber
3. staying in the shade or sun
4. restrict activity to night
THREE DOMAINS, P. 2
THERMOREGULATION CONTINUED…
II. Endothermy – when organisms are able to use thermal energy that is generated by metabolism to
maintain homeostatic body temperatures (they can control their own body temperature)
A. Cooling by evaporation
1. sweating and panting
2. since changing from a liquid to gaseous state requires energy (endergonic), body heat is
removed when water evaporates
B. Warming by metabolism
1. muscle contraction and other metabolic activities generate heat
2. shivering warms animals from the heat generated by muscle contractions
C. Adjusting surface area to regulate temperature
1. Changing the volume of blood that flows to extremities by vasodilation or
vasoconstriction can cause heat to be lost or conserved
2. In hot environments - increase blood flow to extremities
3. In cold - decrease blood flow to extremities to conserve heat
D. Behavioral, physiological, or anatomical adaptations that increase an animal's ability to survive
in a certain environment
1. hibernation
2. hair, feathers, blubber
3. staying in the shade
4. restrict activity to night
CLASSIFICATION - CH 19 - PAGES 308-314
I. TAXONOMY - Study of the grouping of organisms
A. Taxon- group of organisms defined by the classification scheme
B. Levels of Taxa – Domain, Kingdom, Phylum (in animals)/Division (in plants), Class, Order,
Family, Genus, Species
C. Three Domains, Six Kingdoms – Listed from most primitive to most advanced
1. Domain Archaea – Kingdom Archaebacteria
2. Domain Bacteria – Kingdom Eubacteria
3. Domain Eukarya
a. Kingdom Protista - euglena, amoeba, paramecium, algae
b. Kingdom Fungi
c. Kingdom Plantae - ferns, gymnosperms, angiosperms
d. Kingom Animalia - vertebrates, invertebrates
II. BINOMIAL NOMENCLATURE - The naming of an organism
A. The scientific name of an organism is: Genus/species
1. Homo sapiens - humans
2. Felis domesticus - house cat
3. Ursus horribilis - brown bear
B. Rules
1. Capitalize 1st letter of genus name
2. Underline genus and species names
3. 1st use of name must be written out in each paragraph
4. After 1st use - abbreviate genus name to 1st letter
H. sapiens
U. horribilis
III. Types of Taxonomy – both are used in classification
A. MorphologicalTaxonomy
1. Carolus Linnaeus - the Swedish botanist who was the first to start classifying organisms
2. This system classifies organisms based on observable physical characteristics
B. Systematic Taxonomy
1. This system uses phylogeny (the evolutionary history of a species of group of related
species) to group organisms
2. This system classifies organisms by lines of evolutionary descent
THREE DOMAINS, P. 3
III. EVOLUTIONARY SYSTEMATICS
A. Study of relationships between organisms in order to develop phylogenetic evolutionary lines
and taxonomic classification
B. Cladistics
1. an approach to classification that organizes all the organisms into evolutionary
branch
2. organizing the branches according to the order in which they arose evolutionarily based
on shared derived characteristics (characteristics that were passed down from their
ancestors)
C. Phylogenetic Tree/ Cladogram
1. are graphical representations (models) of evolutionary history that can be tested
2. they show genealogies of probable evolutionary relationships among species and other
groups
pages 310 - 313
a. monophyletic - represents one evolutionary line; is the ideal in classification
b. polyphyletic - represents multiple evolutionary lines - organisms evolved from
more than one source
D. General Information - Phylogenetic trees and cladograms
1. Show that all organisms share a common ancestral origin of life
2. Can represent traits that are either derived or lost due to evolution, such as the number of
heart chambers in animals, or the evolution of opposable thumbs, or the absence of
legs in some sea mammals
3. Illustrate speciation that has occurred – when there is a new “branch” on the tree
4. The relatedness of any two groups on the tree is shown by how recently two groups had a
common ancestor – the more recently they shared a common ancestor, the more
closely related they are
5. Are dynamic (are constantly being revised and/or created) based on:
a. the biological data used
b. new mathematical and computational ideas
c. current and emerging knowledge – such as advancements in technology or the
discovery of a new species
E. Phlyogenetic trees and cladograms can be constructed:
1. from morphological similarities of living or fossil species
2. from DNA and protein sequence similarities
3. by employing computer programs that have sophisticated ways of measuring and
representing relatedness among organisms
4. by comparing organisms’ physical (morphological) traits
5. by comparing organisms’ biochemical make-up – the makeup of their organic molecules,
such as comparing the amino acid sequence in their proteins
6. by comparing organisms’ genetic make-up – the makeup of their DNA and genes,
such as comparing the nucleotide sequence in their DNA
7. by using paleontogical (fossil) evidence
8. by testing for homology = same origin
Homologous structure – have a common ancestor; not necessarily the same function
or appearance (Ex. forelimbs of vertebrates)
9. by examining life cycle stages and patterns of embryonic development, such as fetal
structures, larval structures, gametes or reproductive mechanisms
10. Figure 19.19 page 314
THREE DOMAINS, P. 4
SPECIATION
I. Speciation - The formation of a new species
A. Species
1. Definition - a population whose members can interbreed with one another to produce
viable, fertile offspring but cannot (or at least usually do not) interbreed with members of other groups
2. Essential feature of the definition - reproductive isolation (genetic isolation)
3. Two separate species exist when the two can occupy the same space without interbreeding
4. Members of a species share a common gene pool that is separated from the gene pools of
other species
(Gene pool = all the genes available within a species)
B. Speciation may occur when two populations become reproductively isolated from each other –
when there is no gene flow between the populations
C. Types of Speciation
1. Allopatric speciation - speciation that is the result of the geographic separation of a
population of organisms
2. Sympatric speciation - speciation that occurs without geographic isolation
D. Allopatric speciation
1. Examples of geographic barriers – islands, rivers, mountain, lake, trees
2. Description of how allopatric speciation occurs
a. Once a population has been geographically separated from the parent population,
it may begin to diverge genetically if the separated group and the parent
group are under different selective pressures
b. IF enough time passes (thousands or even millions of years) AND the selective
pressures are sufficiently great, the isolated population may diverge so much
that, even if it were reunited with the parent population, interbreeding under
natural conditions would no longer occur. Speciation is said to have taken place.
c. Every isolated population does not become a species
E. Sympatric speciation - species can be formed two ways
1. by polyploidy - an increase in the number of chromosomes beyond the typical diploid
a. often occurs as a result of nondisjunction (when the chromosomes don't separate
during meiosis)
b. fairly common in plants, but rare in animals
c. this type of speciation would be rapid – it wouldn’t take large amounts of time
2. by disruptive natural selection, when 2 extreme traits are selected over the “average” trait
II. Maintaining Genetic Isolation
A. isolating mechanisms - that thing that keeps two species from mating and preventing gene flow
between the two species
B. Two types of isolating mechanisms
1. premating isolating mechanisms (Prezygotic barriers)- which prevent mating between
members of different species
a mechanical isolation - the male and female reproductive don't match; no lock and
key fit
b. temporal isolation - two species are separated by time or seasons
c. behavioral isolation - certain behavior or rituals are necessary for mating to occur
2. postmating isolating mechanisms (Postzygotic barriers) - which prevent the production
of fertile offspring from matings between members of the two species
a. Hybrid inviability – the embryo or baby formed by the two different species dies
b. Hybrid sterility - the baby formed by the two different species is sterile (can’t
have babies itself)
c. Gamete isolation – the sperm and the egg (gametes) of the two different species
don’t recognize each other
THREE DOMAINS, P. 5
HOMEOSTASIS AND FEEDBACK MECHANISMS
I. The goal of an organism’s body = to maintain homeostasis, the narrow limits of the stable, internal
conditions necessary to keep an organism alive
II. Organisms use feedback mechanisms to maintain their internal environments and respond to external
environmental changes
A. Negative feedback
1. helps to maintain homeostasis for a particular condition (variable) by regulating
physiological processes, and returning the changing condition back to its target set
point (it returns the organism to homeostasis)
2. How it works:
a. Control center (usually the brain) constantly monitors conditions using receptors
b. a sensing mechanism (receptor) detects a change in conditions beyond specific
limits
c. the control center, or integrator, evaluates the change and activates a second
mechanism (an effector) to correct the condition and return conditions to its
original state (its set point)
d. When the control center determines that conditions have returned to normal,
corrective action is discontinued
3. Overall result: the original condition is canceled, or negated, so that conditions are
returned to normal
4. Examples:
a. operons in gene regulation – sections of DNA that turn genes on and off
b. temperature regulation in animals
c. plant responses to water limitations
B. Positive feedback
1. an action (stimulus) intensifies a condition so that it is driven further beyond normal
limits – it amplifies responses and processes
2. the variable initiating the response is moved farther away from the initial set-point.
3. Amplification occurs when the stimulus is further activated which, in turn, initiates
an additional response that produces system change
4. The amplification continues until the stimulus is removed
5. is uncommon, but does occur during:
a. childbirth (labor contractions)
b. lactation (where milk production increases in response to an increase in nursing)
c.. Ripening of fruit – in some fruits, it is controlled by the hormone ethylene (it
causes the fruit to get fleshy and turn colors). As the levels of ethylene rise,
positive feedback causes even more ethylene to be produced.
III. Alteration in the mechanism of feedback often results in deleterious (harmful) consequences
A. Normal Function: When sugar is in the blood, insulin is supposed to be released by the body so
that the sugar can get out of the blood and into the cells. An increase in blood sugar causes a
release of insulin, which causes a decrease in blood sugar because the sugar leaves the blood
and goes into the cells.
Diabetes is caused when negative feedback in the body doesn’t respond properly to sugar levels
in the blood. In diabetes, this negative feedback doesn’t occur because insulin doesn’t work
properly – it doesn’t get the sugar out of the blood.
B. Normal Function: As the level of water in the blood falls, the brain releases a hormone that tells
the body to release the antidiuretic hormone (ADH), which tells the kidneys not to get rid of
much water in its urine. In this way, negative feedback ensures that the amount of ADH
rises when the water level in the blood is low. As the level of the water in the blood rises,
negative feedback causes ADH to stop being released.
THREE DOMAINS, P. 6
Dehydration occurs in response to decreased antidiuretic hormone because the body gets rid of
too much water. This could be caused if the brain isn’t working properly and it doesn’t send
out the signal that ADH should be released
C. Blood clotting
IV. Organisms respond to changes in their environment through behavioral and physiological
mechanisms in an effort to maintain homeostasis
1. Photoperiodism in plants
4. Phototropism in plants
2. Hibernation in animals
5. Migration in animals
3. Taxis in animals
6. Chemotaxis in bacteria
V. Homeostatic control systems in organisms support common ancestry (that all organisms share a
common ancestor)
A. Excretory systems in flatworms, earthworms, and vertebrates are all similar
B. Osmoregulation in bacteria, fish, and protists – they all match their body osmolarity to their
environment
C. Osmoregulation in aquatic and terrestrial plants – they all use a vacuole and stomata
D. Circulatory systems in fish, amphibians, and mammals – blood vessels, heart, etc
E. Thermoregulation in aquatic and terrestrial animals – they all use countercurrent exchange
mechanisms
TIMING AND COORDINATION OF PHYSIOLOGICAL
EVENTS ARE REGULATED BY MULTIPLE MECHANISMS
I. In animals, internal and external signals regulate a variety of physiological responses that
synchronize with environmental cycles and cues
A. Circadian rhythms (the physiological cycle of about 24 hours)
B. Nocturnal cycles or sleep/awake cycles
C. Seasonal responses, such as hibernation, estivation, and migration
D. Release and reaction to pheromones
E. Visual displays in the reproductive cycle
II. In fungi, protists and bacteria, internal and external signals regulate a variety of physiological
responses that synchronize with environmental cycles and cues
A. Fruiting body formation in fungi slime molds and certain types of bacteria
B. Quorum sensing in bacteria – stimulus and response is correlated to population density
III. Individuals can act on information and communicate it to others
A. Organisms exchange information with each other in response to internal changes and external
cues, which can change behavior. Examples:
1. Fight or flight response
2. Predator warnings
3. protection of young
4. Plant-plant interaction due to herbivory
5. Avoidance responses
B. Animals use visual, audible, tactile, electrical and chemical signals to communicate between
themselves. This occurs through various mechanisms which the organisms use to indicate
dominance, find food, establish territory and ensure reproductive success
1. Bee dances
7. colony and swarming behavior in insects
2. birds songs
8. coloration
3. territorial markings in mammals
4. pack behavior in animals
5. herd, flock, and schooling behavior in animals
6. predator warning