Summary

Comparative anatomy

• Organisms have similar structure (homologies) even if they have different ecologies
• Vestigial organs imply trace of earlier history
• Ontogeny shows divergent adult morphologies started from very similar beginings

Taxonomy

• Life is hierarchical (a "tree of life")

Geology

• Earth is ancient
• Small processes over time yield big changes
• Fossils occur in the order predicted by comparative anatomy

Biogeography

• The same environment in different continents yields different organisms