1. Evidence of Evolution

2. Darwin
Argued that living things have been evolving on Earth for millions of years

3. The Fossil Record Darwin saw fossils as a record of history on Earth
By comparing fossils from older rock layers (lower layers) to fossils from younger layers (upper layers), scientists could document that fact that life on Earth has changed over time.

4. Geographic Distribution of Living Species
Many times, animals on different islands or continents were this way due to climate.
Remember however, that some continents had similar environments but different organisms

5. Homologous Body Structures
Scientists noticed anatomical similarities between existing organisms
Many have different functions but are constructed from similar bones
Each of these limbs has adapted in ways that enable organisms to survive in different environments
These similarities and differences help biologists group animals according to how recently they last shared a common ancestor

6. Homologous Structures
Structures that have different mature forms but develop from the same embryonic tissue
Ex: bones in the flipper of a whale and bones in the arms of humans

7. Analogous Structures
Serve the same function in different species but evolved independently.
Ex: wings of butterfly, bat, and bird

8. Vestigial Organs An organ that serves no useful function in organisms.
Ex: appendix, tonsils

9. Similarities in Embryology
The embryos of many organisms are very similar (vertebrates)