| A | B |
|---|
| natural selection | organisms with traits well suited to an environment are more likely to survive |
| half-life | the time it takes for one-half of a sample of radioactive atoms in a sample to decay |
| radioactive dating | technique used to measure the rate of decay of certain elements in order to determine the age of the sample |
| homologous structure | structures that share a common ancestry, examples - bird wing, dolphin fin, and human arm |
| vestigial structure | structures with no apparent function - examples are appendix and whale's pelvic girdle |
| adaptation | is the process by which a species becomes better suited to its environment |
| balancing selection | the situation in which two opposing selective forces affect the frequency of an allele in a population - example Sickle-cell and Malaria in Africa |
| directional selection | unopposed selection that changes the frequency of an allele toward one direction - example very large tortoises on an island |
| ecological race | populations of the same species that differ genetically because they have adapted to different conditions - sparrows across the US |
| divergence | accumulation of differences between species or populations - example Galapagos finches |
| gradualism | hypothesis that evolution is occuring at a constant rate |
| punctuated equilibria | hypothesis that evolution is occuring at irregular rates |
