| A | B |
|---|
| Endosymbionts | a group of organisms that lives within other organisms and may perform specific functions for the host |
| Speciation | the creation of new species |
| Species | a population composed of individuals able to interbreed to create viable, fertile offspring |
| Punctuated equilibrium | the theory that drastic changes create new species that then change very little over time |
| Gradualism | the theory that species evolve gradually and consistently over time |
| Extinction | the complete elimination of all members of a species or population |
| Mass extinction | a worldwide event in which large numbers of species simultaneously experience extinction |
| Common Ancestor | a species (usually extinct) from which a group of species evolved |
| Fossil | preserved traces or remains of living organisms from the past |
| Biogeography | the study of the distribution of species, organisms, and ecosystems through geologic space and time |
| Homology | the similar features between different organisms resulting from common ancestry |
| Anatomical homology | a group of similar structures between different organisms that is said to result from common ancestry, like the forelimb of animals |
| Molecular Homology | similar stretches of DNA between different organisms that is said to result from common ancestry |
| Developmental Homology | the similar features in the embryos of different organ isms that is said to result from common ancestry |
| Hox gene | the sections of the genome that allow embryos to develop structures in the correct place |
