1. Evidence for Evolution

2. Five main examples of Evidence for Evolution
Fossils
Geographical Distribution
Embryology
Comparative Anatomy
Molecular and Genetic

3. #1 Fossil Evidence Fossils
The oldest fossil on record is estimated 3.7 billion years old
Fossils in older layers are more primitive than those in the upper layers.
It can be easy to see the progression of life from ancient fossils to modern organisms.

4. Types of Fossils
Permineralization occurs when minerals carried by water are deposited around a hard structure
A natural cast forms when flowing water removes all of the original tissue, leaving an impression.

5. Types of Fossils
Amber-preserved fossils are organisms that become trapped in tree sap that hardens after the tree is buried.

6. Types of Fossils Impressions are imprints left in sedimentary rock
Preserved remains form when an entire organism becomes encased in material such as ice, ash, tar …

7. Why don’t all organisms get fossilized?
Some organisms’ soft body types just don’t fossilize well (fungus, jellyfish, etc.)
Very specific conditions are required for fossils to form; many places on Earth are geographically unsuitable for fossils to form
Scientists are still finding new fossils everyday; we have not found every fossil yet!

8. #2 Geographical Distribution
similar species are found in similar environments or the same area
Island species most closely resemble nearest mainland species
Populations can show variation from one island to another

9. #2 Geographical Distribution
The same fossil species can be found across continents
The continents were all once connected into the super-continent Pangea

10. #3 Embryology
Embryos (early developmental stage) show evidence of evolution
Some related species have almost identical larvae, but different adult body forms
All vertebrates have similar embryos which differentiate as the specific organism grows up
Larva
Adult barnacle
Adult crab

11. Which is the human?

12. How about now? Can you tell yet?

14. #3 Embryology
Vertebrates all share gill slits and a tail in their early embryo stage; this is evidence they share a common ancestor (a fish)

15. #4 Comparative Anatomy
The study of anatomy provides evidence of evolution; we can see the similarities in body structure of related organisms
Homologous structures are similar in structure but different in function.
Homologous structures ARE EVIDENCE of a common ancestor.

16. Homologous Structures
ARM
LEG
Wing
Flipper
grasping
walking
swimming
flight

17. #4 Comparative Anatomy
Analogous structures are similar in function but differ in structure
Analogous structures DO NOT show common ancestry
Fly wing
Bat wing

18. Structural patterns are clues to the history of a species.
Vestigial structures are remnants of organs or structures that had a function in an early ancestor.
Examples include ostrich wings, human appendix and wisdom teeth, whale and snake pelvis/hind legs

19. Pythons have tiny claws where their ancestors had legs

20. #5 Molecular and Genetic Evidence
AKA Biochemical Evidence
Two closely-related organisms will have similar DNA, RNA, and protein (amino acid) sequences.
This is the best evidence for evolution because it is an exact measure of how genetically similar two organisms are.