1. Evidence of Evolution

2. The Fossil Record
Darwin saw fossils as a record of the history of life on Earth
Darwin proposed that the Earth was many millions of years old
Countless species had come into being, lived for a time and then vanished
By comparing fossils from older layers with fossils from younger layers you could document that life on Earth has changed over time

3. Geographic Distribution of Species
Similar but unrelated species puzzled Darwin
Similar animals in different locations were the product of different lines of evolutionary descent

4. Homologous Body Structures
Anatomical similarities among the body parts of animals with backbones
Example: limbs of reptiles, birds, and mammals
Vary greatly in form and function
Constructed from the same basic bones.

5. Homologous Body Structures
Homologous structures— structures that have different mature forms but develop from the same embryonic tissues
These similarities and differences help biologists group animals according to how recently they last shared a common ancestor

6. Vestigial Organs Not all structures serve important functions
Organs of many animals are so reducing size that they are just vestiges, or traces, of homologous organs in other species
Why would this happen?
One possibility is that the presence of a vestigial organ does not affect an organism’s ability to survive

7. Embryology
Early stages, embryos, of many animals with backbones are very similar
Demonstrates that the same groups of embryonic cells develop in the same order of all vertebrates.
Common cells and tissues, growing in similar ways, produce homologous structures.