1. Stratigraphy The study of layers of the earth’s crust
The layers are called strata

2. Stratigraphy If you look at a cross section of rock
the lower layers are older rock
the upper layers are younger rock.

3. Stratigraphy Fossils in the lower layers are older fossils
Fossils in the upper layers are younger

4. Homologous structures
These are structures that look similar in a large group of animals but may have different functions.
Examples: hands in animals to the right

5. Vestigial structures
features of the body that may be fully functional in some animals, but with no known functions in others.
Evolutionary leftovers
Appendix
Tail bone