| A | B |
|---|
| paleontologist | person who studies fossils |
| relative dating | way to find age of a fossil by comparing its placement with fossils in other rock layers |
| radioactive dating | most accurate way to find age based on amount of radioactive isotope it contains |
| absolute dating | also called radioactive dating |
| geologic time scale | scale used to show evolutionary time |
| era | subdivision of time on geologic time scale after Precambrian Time |
| Precambrian Time | 90% of earth history; few fossils; life only in seas |
| Paleozoic Era | first era; explosion of life |
| Mesozoic Era | second era; dinosaurs; firs mammals; flowering plants |
| Cenozoic Era | third era; mammals dominate |
| punctuated equilibrium | rapid change in a line of descent |
| extinct | species died out |
| gradualism | slow steady change in a line of descent |
