| A | B |
|---|
| Fossil | remains or traces of a once-living |
| Petrified Remains | fossils that form when some or all of the original materials that made up |
| Carbonaceous Film | fossil formed when the remains of a once-living organism are subjected to heatand pressure |
| Mold | fossil formed when an organism is buried,decays,and leaves behind a hollow place in the rock |
| Cast | fossil formed when sediments fill a mold and hardens into rock |
| Index Fossils | fossils of species that existed on Earth for only a short time, were abundant, and were widespread the age of rock layer |
| Principle of Superposition | states that for undisturbed layers of rocks, older rocks lie underneath younger and younger rocks |
| Relative Dating | method to determine the orders of events and relative age of the rocks by examining the positive of rocks in a sequence |
| Unconformity | gaps in the rocks layers due to erosion, normal, or both |
| Absolute Dating | process that uses the preperties of atoms in rocks and other objects to determine their exact ages, in years |
| Radioactive Decay | process in which the decay of an atoms of an isotope results in a change in the numbers of protons and the formation of a new element |
| Half Life | time it takes for half the atoms in a radioactive isotope to decay |
| Radiometric Dating | process to determine the absolute ages of rocks by measuring the amounts of parents and daughter materials in a rock and by knowing the half-life of the parent |
| Uniformitarianism | states that Earth process happening today are similar to these that happened in the past` |
| Species | group of similar organisms that can successfully reproduce among themselves in their natural enviroment |
| Evolution | changes in the inheritied features of a space over time; can occur slowly and rapidly |
| Variation | an inheritied trait that makes an individual different from other members of the same species |
| Gradualism | model of evolution that shows a slow change of one species to another, new species through continued mutations and variations over time |
| Radioactive Element | element that gives off radioactive due to an unstable nucleus |
| Embroyology | study of development in organisms |
