| A | B |
|---|
| extinct | term used to refer to a species that has died out |
| paleontologist | scientist who studies fossils |
| relative dating | method of determining the age of a fossil by comparing its placement with that of fossils in other rock layers |
| index fossil | distinctive fossil that is used to compare the relative ages of fossils |
| radiometric dating | method for determining the age of a sample from the amount of a radioactive isotope to the non-radioactive isotope of the same element in a sample |
| half-life | length of time required for half of the radioactive atoms in a sample to decay |
| geologic time scale | timeline used to represent Earth's history |
| era | major division of geologic time; usually divided into two or more periods |
| period | division of geologic time into which eras are subdivided |
| plate tectonics | geologic processes, such as continental drift, volcanoes, and earthquakes, resulting from plate movement |
| macroevolutionary patterns | changes in anatomy, phylogeny, ecology, and behavior that take place in clades larger than a single species |
| background extinction | extinction caused by slow and steady process of natural selection |
| mass extinction | event during which many species become extinct during a relatively short period of time |
| gradualism | the evolution of a species by gradual accumulation of small genetic changes over long periods of time |
| punctuated equilibrium | pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change |
| adaptive radiation | process by which a single species or a small group of species evolves into several different forms that live in different ways |
| convergent evolution | process by which unrelated organisms independently evolve similarities when adapting to similar environments |
| coevolution | process by which two species evolve in response to changes in each other over time |
| endosymbiotic theory | theory that proposes that eukaryotic cells formed from a symbiotic relationship among several different prokaryotic cells |
