Classification and Biodiversity
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Characteristics of Living Things
We've already listed characteristics of living things that separate them from non­living material. Page 104 in your text gives another list, similar to the one we had used. Some of the wording is different, but it is basically the same:
*Living things are organized systems made up of one or more cells
*Living things metabolize matter and energy
*Living things interact with their environment and are homeostatic
*Living things grow and develop
*Living things reproduce themselves (and living things can only come
from other living things)
*Living things are adapted to their surroundings
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Classification
Scientists classify organisms into groups. Why is this important?
Classification allows us to organize living things in ways that help us understand them. They are grouped based on many criteria, placing those that have similar characteristics or those that are closely related together, and separating them from others which are more distantly related.
One thing important to understand is that classification is based on scientist's best understanding of how organisms are related, and that this is constantly being revised. Not all scientists agree completely with the current system; many changes have been made over time...and many more will likely be made in the future.
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Six Kingdoms
All organisms are currently placed into one of six kingdoms of living things .
Read pages 102­105 in your text, and with a partner create a chart listing the six kingdoms, with a brief description of the organisms in each one.
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Six Kingdoms: Complete the Chart
Kingdom:
Kingdom:
Kingdom:
Kingdom:
All Living Things
Kingdom:
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Kingdom:
Three Domains of Life
What are the two major types of cells that were studied earlier in this course?
Prokaryotic:
Cells which do not contain a nucleus or other membrane­bound organelles (ex: bacteria)
Eukaryotic:
Cells which contain a nucleus and several other
membrane­bound organelles (ex: plant cells, animal cells)
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Three Domains of Life
Read pages 106­107 and list the three domains of life, including their characteristics and which of the six kingdoms fall under each one.
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Three Domains of Life
Domain
Characteristics
Kingdoms
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Discussion Questions
Would a group identified as "flying animals" be useful to a biologist? Explain.
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Discussion Questions
Why is it beneficial for all scientists to use the same system to classify living things?
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Homework
Read pages 108­116 in Section 4.2 of your text, stopping when you reach the subsection titled "Phylogeny".
Complete Questions #1­3 and 5­7 on page 121.
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Naming and Classifying Organisms
The practice of classifying organisms is called taxonomy .
All organisms are arranged into groups based on various criteria.
The groups form a hierarchy...with each group becoming more specific and containing fewer organisms.
As we have already seen, all living things are currently divided into six kingdoms...the largest and least specific groups in the hierarchy.
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Naming and Classifying Organisms
There are six more groups beneath the kingdoms. Each is made up of one or more groups from the next level down.
For example, the kingdom animalia contains over 30 phyla (single: phylum), with over 95% of all animals falling under the nine most common phyla.
The levels of classification are, in order from least to most specific are:
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
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The number of different groups at each level varies greatly, but there is only a single type of organism for each species.
An organism's scientific name is made up of the final two groups: genus and species
Example of Taxonomy
This system allows scientists to give a complete taxonomy for any organism. For example, the taxonomy for a great white shark would be:
Kingdom
Animalia
Phylum
Chordata (subphylum vertebrata)
Class
Chondrichthyes (subclass elasmobranchii)
Order
Lamniformes
Family
Lamnidae
Genus
Carcharodon
Species
carcharias
Scientific name: Carcharodon carcharias
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Notice that some groups may be divided into subgroups, which are more specific. When writing the scientific name, use both the genus and species; the genus is written beginning with a capital, the species in all lowercase, and if typed the scientific name is in italics.
Binomial Nomenclature
Using both the genus and species give each organism a two­part name...this is called binomal nomenclature .
What types of evidence to biologists use when arranging organisms into these groups?
Review pages 113­116 in your text, and list the five major sources of evidence used for classifying organisms. Include a brief description of what each one involves.
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Evidence Used in Taxonomy
First, list the five major sources of evidence used for classifying organisms:
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en
ce
Evidence Used in Taxonomy
Briefly describe each type:
ce
n
e
d
or
id
v
E
c
e
R
il s
s
o
F
Embryonic Develoment
Evidence
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Review of Homework
Read pages 108­116 in Section 4.2 of your text, stopping when you reach the subsection titled "Phylogeny".
Complete Questions #1­3 and 5­7 on page 121.
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Homework
1.
List two reasons why the system of binomial nomenclature is useful.
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Homework
2.
Cats, goldfish, and humans are in the same phylum.
What characteristics do they have in common?
What characteristics place cats and humans in a different order
from goldfish?
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Homework
3.
Based on your own knowledge, place the following species into three
different phyla:
Spider
Ant
Snail
Crow
Turtle
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Octopus
Salmon
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Homework
5.
Referring to the table shown here, which two animals
are most closely related? Explain your answer.
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Homework
6.
The information in this table shows that a skunk is more closely
related to a coyote than it is to a bat. Explain how you know this.
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Homework
7.
What kind of animal is Myotis myotis ? How do you know?
Use the table shown here to help you.
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Phylogeny
When species are put into groups, we are making a hypothesis about their phylogeny, or evolutionary history. In other words, species are separated based on how we believe they are descended from common ancestors. The more closely grouped they are, the more recently scientists believe they shared a common ancestor, and the more closely related they are believed to be.
A classification scheme based on phylogeny is called cladistics, and is used to create diagrams similar to family trees, showing how closely related, in evolutionary terms, we think species are.
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Phylogeny
For example, wolves, cougars, and lynx are all North American predators. They are all classified in the order carnivora. However, the lynx and cougars are also in the same family (Felidae) while wolves are placed in a separate family (Canidae). This indicates that, while all three are thought to have a common ancestor, the belief is that the lineage which produced lynx and cougars separated from wolves at some point, and then developed into separate species later.
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Homework
Read pages 116­120 in Section 4.2 and pages 162­167 in Section 6.1 of your text.
Complete Questions #12 on page 121, #20­22 on page 128­129, and #1 on page 168.
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Homework
#12, page 121
Describe the relationships in the following phylogeny diagram. Whic two species are most closely related? Explain your answer.
Fish P
2 dorsal fins
feathery tail
Fish Q
2 dorsal fins
short, blunt tail
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Fish R
2 dorsal fins
short, blunt tail
Homework
#20, page 128
Imagine that four new species of birds have been discovered. All have similar decorative plumage on their heads. Three have tails that are longer than their bodies. Two of the long­tailed birds have beaks that are sharp and hooked, while the third has a long slender beak. Using this invormation, draw a cladogram showing the probable evolutionary relationships of these birds. Indicate on the cladogram where the shared characteristics probably arose.
First, sketch simple diagrams of the characteristics:
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Homework
#20, page 128
Now create the cladogram:
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Homework
#21, page 128
Study the cladogram shown here. Which animal is most closely related to the squirrel? Which two animals are most dissimilar? Which animals have limbs?
hagfish
frog
squirrel
polar bear
hair
limbs
vertebrae
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Homework
#22, page 129
Based on the phylogenetic tree diagram on page 129, state whether each of the following statements is true or false.
(a)
The giant panda's closest living relative is the red panda.
(b) Pandas, bears, and raccoons all have a common ancestor.
(c)
The most recent common ancestor of giant pandas and bears is
different from the most recent common ancestor of red pandas and raccoons.
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Homework
#1, page 168
Design a graphic organizer to compare plants and animals.
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eagle
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horse
polar bear
leopard
tiger
Dichotomous Keys
A dichotomous key is a useful tool that is commonly used when attempting to classify an unknown organism. The key uses paired descriptive statements to narrow the classification of an organism, leading toward the species name.
A simple example of a dichotomous key might be:
1.
The organism has wings.......Go to 2
The organism does not have wings.........Ant
2.
The organism has a striped body and transparent wings.........Bee
The organism has broad, black and orange wings........Butterfly
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Using a Sample Dichotomous Key
Scientists have discovered a previously unknown island in the Pacific Ocean, and named it New Pamisham. Several new creatures have been identified, and organized into species. The zoo you work for has collected a group of these organisms, and you are responsible for identifying them.
Use the dichotomous key handouts to classify the organisms on the following page. Write your answers in the spaces provided on your sheet.
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Thinking Lab: Animal Similarities and Differences
Read the thinking lab on page 167, and use the pictures below to answer the questions.
garden eel
cat
crab
centipede
butterfly
orangutan
frog
grasshopper
octopus
oyster
earthworm
jellyfish
Arctic char
Herring
gull
snail
snake
sponge
starfish
tapeworm
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horseshoe crab
spider
Animal Phyla
Porifera
Cnidaria
Platyhelminthes
Mollusca
sponge
jellyfish
tapeworm
snail
octopus
oyster
Annelida
Arthropoda
Echinodermata
Chordata
earthworm
butterfly
crab
centipede
horseshoe crab
spider
grasshopper
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starfish
cat
orangutan
garden eel
Arctic char
herring gull
snake
frog
Homework
1) Read pages 182­186 in Section 6.3 of your text. 2) Use the information to create a chart of the five major characteristics biologists use to group species from the kingom animalia into different phyla.
3) List the characteristics, and describe what is meant by each one.
4) Read pages 186­189 and create a graphic chart to display the major physical characteristics of arthropods. How do these characteristics help make this group so successful?
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Homework
2) Use the information to create a chart of the five major characteristics biologists use to group species from the kingom animalia into different phyla.
What are the five characteristics?
1) Number of germ layers
2) Digestive tract
3) Body symmetry
4) Development of a coelum
5) Reproduction
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Number of Germ Layers
Most animals have three germ layers, or layers of tissue in early development that specialize into the body tissues later. The three layers are:
Ectoderm
*in mammals, this develops into the skin, nerves, and some sense organs
Mesoderm
*in mammals, this develops into the muscles, blood, kidneys, and reproductive organs
Endoderm
*in mammals, this develops into the lungs, liver, and digestive organs
Two of the phyla only have two. Which are these?
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Number of Germ Layers
Ectoderm: forms skin and nervous system
Mesoderm: forms kidneys, skeleton, muscles,
blood vessels, gonads
Endoderm: forms lungs and lining of digestive tract
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Digestive Tract
The poriferans (sponges) are the only animals which digest food intracellularly. What does this mean?
All other phyla digest their food, at least partially, extracellularly.
What is the difference between an incomplete and a complete digestive tract?
What are examples of phyla with an incomplete digestive tract?
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Body Symmetry
What is meant by symmetry?
What is the only animal that displays assymetry?
Explain the difference between radial and bilateral symmetry.
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Development of a Coelum
A coelum is a fluid­filled body cavity in which the digestive tract and other organs are suspended. Remember in both the earthworm and frog, the organs were inside a body cavity. Annelids, nematodes, molluscs, arthropods, and chordates all have a coelum, and are called coelumates. All other phyla lack this feature, and are called acoelumates.
A coelum provides animals with more strength for their muscles to brace against, because of the fluid pressure. It also allows the development of more complex organs.
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Reproduction
All animals are capable of sexual reproduction, but some are also able to reproduce asexually. Poriferans and cnidarians can reproduce by budding .
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Reproduction
All animals can also produce sperm and eggs, which combine to produce new offspring which share characteristics of both parents.
Some animals, such as earthworms, are hermaphrodites , which contain both male and female reproductive organs.
In more complex animals, individuals carry only male or female reproductive organs. The method of fertilization, and how the young are produced (for example, laying eggs or having live young) may be used to divide the species into different groups.
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Reproduction
What is parthenogenesis?
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Arthropods
Read pages 186­189 and create a graphic chart to display the major physical characteristics of arthropods. How do these characteristics help make this group so successful?
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Insects
What are the specific characteristics of insects that separate them from the other arthropods?
How does the life cycle of insects contribute to their success?
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Chordates
Read pages 190­194
1) What characteristics separate the chordates from the other animal phyla? 2) Create a chart comparing the major vertebrate classes:
Chondrichthyes (cartilaginous fish)
Osteichthyes (bony fish)
Amphibia
Reptilia
Aves (birds)
Mammalia
Include the major physical characteristics which separate these classes.
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dorsal fin
caudal fin
pectoral fin
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