| A | B |
|---|
| perpetual change | The earth is neither constant or cycling but always changing |
| adaptation | a trait that makes an organism more likely to survive and reproduce |
| common descent | similar species share their ancestry |
| homologous structure | similar function and structure amongst a group of species |
| vestigial structure | human appendix, pelvic girdle in whales |
| natural selection | organisms most well-suited to their environment are more likely to survive and reproduce |
| stable selection | organisms with the "middle of the road" trait are most successful |
| directional selection | one extreme of a trait is most successful |
| disruptive selection | both extremes of a trait are most successful |
| Hardy-Weinberg Equilibrium | A gene pool will remain stable if evolution is not occurring |
| homozygous | having two identical alleles for a trait |
| heterozygous | having a dominant and recessive allele for a trait |
| allele | alternate form of a gene |
| gene flow | immigration and emigration causes this |
| genetic drift | disruption of the gene pool due to random events |
| convergent evolution | species that do not share a common ancestor evolve similar traits |
| divergent evolution | species that evolve from a common ancestor evolve similar traits |
| allopatric speciation | new species arise due to geographic isolation |
| sympatric speciation | new species arise due to reproductive isolation |
| prezygotic isolation | reproductive barriers prior to mating |
| postzygotic isolation | reproductive barriers that occur after mating |
| gene frequency | the occurrence of a trait within a population |
| species | organisms that have a similar appearance, can reproduce, and give rise to viable offspring |
| morphology | an organism's appearance / body structure |
| fitness | a measure of how likely it is that an organism will survive and reproduce |
| fossil | remnant of a past life |
