1. Modern Evolutionary Classification Notes- Ch. 18.2

3. Evolutionary Classification
Modern classification is based on evolutionary theory
Phylogeny – study of how orgs are related to each other (their evo relationships)
Evolutionary Classification – grouping organisms based on their evolutionary history
Species within a genus are more closely related to each other than species in another genus because all members of a genus share a recent common ancestor
All genera in a family share a common ancestor – further away in the past then the ancestor of any genus in the family
Higher the level of the taxon, the farther back in time the common ancestor
Similar appearance not necessarily sharing a recent common ancestor (barnacle/limpet example)

4. Homologous Structures
One way to discover relationships is by comparing anatomical structures (body organs and parts).
Parts that are alike in basic structure and origin in several organisms but are not used for the same reason are called homologous structures.
Ex. All above have the same bones and number, used differently- evidence points to common ancestor.

5. Cladograms
Certain features shared by different group of organisms are known as “derived characters.”
Derived characters – characteristics that are in recent parts of lineage but not in older members
Used to make cladograms (aka phylogenetic tree)
The more derived characteristics two organisms share, the closer their evolutionary relationship
Uses only characteristics that evolutionary innovations
Evolutionary innovations – characteristics that arise as lineages evolve over time
Cladograms show how one lineage branched from another in the course of evolution

6. Sample Evolutionary Tree
Small difference
Common Ancestor
Largest difference
Moderate difference
Smallest difference
Relative Time

7. TRADITIONAL CLASSIFICATION
Traditional Classification Vs Cladogram
Section 18-2
Appendages
Conical Shells
Crustaceans
Gastropod
Crab
Barnacle
Limpet
Crab
Barnacle
Limpet
Molted exoskeleton
Segmentation
Tiny free-swimming larva
TRADITIONAL CLASSIFICATION
CLADOGRAM
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8. Traditional Classification Vs Cladogram TRADITIONAL CLASSIFICATION
Section 18-2
Appendages
Conical Shells
Crustaceans
Gastropod
Crab
Barnacle
Limpet
Crab
Barnacle
Limpet
Molted exoskeleton
Segmentation
Tiny free-swimming larva
TRADITIONAL CLASSIFICATION
CLADOGRAM
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10. DNA & RNA All living things have it Compare organisms by genes
More similar = more recent common ancestor
Genes of many organisms show important similarities at the molecular level. Similarities in DNA can be used to help determine classification and evolutionary relationships
Human/yeast share common gene for myosin protein – found in muscles (humans) help internal movement (yeast)
More two species have diverged from one another, or changed in comparison to one another during evolution

11. Molecular Clocks Estimates amount of time since species diverged
Uses mutations as markers
Compare similarities and differences in genes

12. Derived Characters in Organisms
Quick Lab
Derived Characters in Organisms
Organism
Derived Characters
Backbone
Legs
Hair
Earthworm
Absent
Trout
Present
Lizard
Human
Identify the organisms in the table that is the least closely related to the others.
Construct a cladogram of these animals. Do NOT copy the table.
Analysis questions on next slide.

13. 3. Analysis Questions
What trait separates the least closely related organism from the other animals?
List the animals in your cladogram in order of distance from the least closely related organism.
Explain if your cladogram indicates that lizards and humans share a more recent common ancestor than either does with an earthworm.
Where would you insert a frog if you added it to the cladogram? Explain your answer.
Direct students to start with org that lacks at least one characteristic that all others share (students should ID worm).
Refer to Fig 18-7 to start cladogram
Lack of backbone
Trout, liz, human
Yes, lizards and humans shared ancestor that had legs and a backbone and that evolved after the earthworm’s lineage branched off on another evolutionary pathway
A frog would occuby a branch b/w liz andtrout because it has legs. Another characteristic, such as dry sky, would then have to be added to liz.

14. Derived Characters in Organisms
Extra Practice
Derived Characters in Organisms
Organism
Derived Characters
Backbone
Placenta
Foramen Magnum Forward
Tuna
Present
Absent
Horse
Human
1. Construct a cladogram for the info above.
2. Three previously unknown vertebrates have been discovered in a rainforest in South America.
a. “rat-like creature”
b. “iguana-like creature”
c. “goldfish-like creature”
Place these animals on your cladogram and justify your placement.
(backbone) tuna (placenta) horse  (FM forward) human