1. UNITY & DIVERSITY: WHAT’S THE RELATIONSHIP? CLADISTICS

2. WHAT ARE CLADISTICS & TAXONOMY? Cladistics : Method of hypothesizing how one organism is related to another. Taxonomy : system of naming/classifying species Taxon : the name of a group or a single organism

3. WHAT’S A CLADOGRAM? Cladogram: a graphic organizer showing the relationship between organisms

4. WHAT’S THE EVIDENCE? Scientists base their hypotheses on shared characteristics, called a homologous feature Ex. Forelimbs of four-legged animals

5. 3 BASIC ASSUMPTIONS 1. All organisms are related by a common ancestor

6. 3 BASIC ASSUMPTIONS 2. There is a branching (splitting in two) pattern of relationships

7. 3 BASIC ASSUMPTIONS 3. Change in characteristics occurs over time

8. METHODOLOGY “HOW-TO” OF CLADISTICS

9. 1.SAME CLADE The organisms you are organizing must all be part of the same clade, or “branch” Which color represents a clade?

10. 2. DETERMINE THE FEATURES Taxa do not overlap Decide if each taxon has the characteristics or not vertebra +++++++ Boney skeleton - ++++++ 4 limbs -- +++++ Amniotic egg --- ++++ hair --- ++++ Egg w/ shell ----- ++

11. 3. GROUP BY FEATURES Species go on the ends of branches Nodes are common ancestors Features are labeled

12. VOCABULARY Shared (primitive) trait : a characteristic that was present in the common ancestor Derived trait : a characteristic that is different from the common ancestor Outgroup : shares a common ancestor, but is the least related in the clade

13. What is an example of a shared trait ? What is an example of a derived trait ? Which is the outgroup ?

14. 4. RULE OF PARSIMONY If there are multiple possible cladograms, the simplest one (with the least number of changes) is best.

15. READING TREES HOW TO READ A CLADOGRAM

16. STRATEGY Look for the most recent common ancestor (nodes) More recent ancestors will be “higher” Older ancestors will be “lower” Don’t read “along the tips”

17. PRACTICE WITH CLADOGRAMS

21. MORE PRACTICE

22. FINALLY!!!