| A | B |
|---|
| paleontologist | scientist who studies fossils |
| fossil record | information about past life, including the structure of organisms, what they ate, what ate them, in what environment they lived, and the order in which they lived |
| extinct | term used to refer to a species that has died out |
| relative dating | method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock |
| index fossil | distinctive fossil used to compare the relative ages of fossils |
| half-life | length of time required for half of the radioactive atoms in a sample to decay |
| radioactive dating | technique in which scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains |
| geologic time scale | scale used by paleontologists to represent evolutionary time |
| era | one of several subdivisions of time between the Precambrian and the present |
| period | unit of time into which eras are subdivided |
| proteinoid microsphere | tiny bubble, formed of large organic molecules, that has some characteristics of a cell |
| microfossil | microscopic fossil |
| endosymbiotic theory | theory that eukaryotic cells formed from a symbiosis among several different prokaryotic organisms |
| mass extinction | event in which many types of living things become extinct at the same time |
| macroevolution | large-scale evolutionary changes that take place over long periods of time |
| adaptive radiation | process by which a single species or small groups of species evolve into several different forms that live in different ways; rapid growth in the diversity of a group of organisms |
| 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 |
| punctuated equilibrium | pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change |
