1. Evidence for Evolution
4 areas

2. 1. Fossil Record Fossil- evidence of an organism that long ago.
Paleontologists - scientists who study ancient life & fossils

3. How do fossils form? Most fossils – sedimentary rock
Environment determines fossil formation; Very few organisms  fossils

4. Dating Fossils
Relative dating: layers at the bottom are older than those above (approximate age)
Radiometric dating: involves radioactive isotopes C14 & K40 (more exact age)

5. How fossils show evolution
Age & Behavior patterns
Show changes in climate & geography
Shows evolution & adaptation
Problems: Incomplete fossils & Imperfectly preserved

6. Increased food source - vast grasslands
Wider, flatter molars better for eating grass
Grasslands made horses more visible to predators
With hoof-like feet horse can run faster & get away from predators

7. Do you see any similarities among the forelimbs of these animals?
If you said “yes” then you just made a type of observation that scientists use to establish evolutionary relationships among organisms.

8. 2. Anatomy/body structures
Homologous structures = similar structure seen in different groups of organisms
Similar structure, but may have same/different function
Ex. Bones in forelimbs of vertebrates
Implies common ancestor

10. What is a similar feature of these 2 organisms?

11. Analogous Structures
Structures w/similar function, but different structure
Shows evolution but NOT common ancestor
Ex: wings – bats, insects, & birds or fins in dolphins vs fish
Any body part that is similar in function but different in structure is an analogous structure.

12. Vestigial Structures Structures/organs appear to have little/no use
May have been used in ancestor
Indicate evolution

13. Examples Ostrich wings Human appendix
pelvic/hip bones in whales and snakes

14. 3. Embryology Many different animals – same organs as embryos
Ex: embryos of fish, reptiles, birds & mammals all have gill slits
Suggests common ancestor
zebrafish chicken dog human skunk

16. 4. Genetic Comparisons Similarities in DNA/RNA sequences
Shows evolutionary relationships

17. Which 2 insects are most closely related?
Most distantly related?