| A | B |
|---|
| extinction | end of an evolutionary line or the end of a species, family, or larger group of organisms |
| fossil | physical evidence of an organism that lived long ago |
| fossil record | collection of fossils that represents the preserved history of living things on earth |
| homologous structures | body parts of different organisms that are different in detail, but similar in general structure and relation to each other |
| vestigial structures | a type of homologous structure that is no longer used as it is in most other organisms that have it |
| species | a group of organisms that can breed with one another and produce fertile offspring in a natural environment |
| speciation | the process by which new species evolve from old ones |
| reproductive isolation | a separation of populations so that they do not interbreed, allowing natural selection to work differently on each group |
| natural selection | the explanation for evolutionary change proposed by Darwin and Wallace |
| absolute dating | a technique utilizing the known rates of decay of radioactive elements to pinpoint the age of a rock or fossil |
| relative dating | a way of comparing the age of fossils based on the layers of rock in which they are found |
| adaptation | a physical or behavioral trait that helps an organism survive |
| variation | any difference between individuals of the same species |
| competition | struggle for survival due to limited resources |
| cladogram or branching tree | a diagram that shows how different groups of organisms are related in their evolutionary developement |
