Modern Classification

1. Modern Classification Ch. 18-2

2. Phylogeny • Study of evolutionary relationships among organisms • Scientists study which organisms evolved from other organisms • They organize this information in a cladogram using derived characteres

3. Cladogram • Diagram that shows evolutionary relationships among a group of organisms • Derived characters – characteristics that appear in recent evolution, not older members

4. How to Make a Cladogram • First, figure out which characteristics each organism has or doesn’t have – usually use a chart • Second, identify which organism is least closely related to the others. In other words, which organism has the fewest characteristics? • Third, put this organism on your main line. • Fourth, identify which organism left is least closely related to the others. Add it to your line next. Continue until you have placed all the organisms. • Fifth, go back and add in your characteristics. Remember, that if an organism goes before the characteristic, then it doesn’t have it. If it goes after, then it does.

5. Make your own • p. 453 in book

6. Should look like: Human Lizard Trout Earthworm Hair Legs Backbone

7. Answer: • What trait separates the least closely related organism from the other animals? • List the animals in your cladogram in order of distances from the least closely related organism. • Does your cladogram indicate that lizards and humans share a more recent common ancestor than either does with an earthworm? How do you know? • Where would you insert a frog if you added it to the cladogram? Explain.