| A | B |
|---|
| fossil | the trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock |
| index fossil | a fossil that is used to establish the age of a rock layer |
| Continental Drift | the hypothesis that states that the continents once formed a single land mass, broke up, and drifted to their present locations |
| extinction | the death of every member of a species |
| fossil record | a historical sequence of life indicated by fossils found in layers of Earth's crust |
| species | a group of organisms that are closely related and can mate to produce fertile offspring |
| geology | The study of Earth's layers and rocks. |
| What rock type can we more likely find fossils? | Sedimentary |
| What is the time it take for half of the atoms in a radioactive element to break down? | half life |
| What is the name the technique using half life in order to determine the age of a fossil? | radioactive dating |
| What is the principle that states younger rocks lie above older rocks if the layers have not been disturbed? | law of superposition |
| Proterozoic Eon | Multicellular organisms formed at the end of the eon which was from about 2.5 bya to 0.55 bya. |
| Hadean Eon | The oldest of the Precambrian eons; the time between Earth's origin and the formation of the first rocks that have been preserved, layers of the Earth formed, at the first toxic atmosphere formed. |
| Archean Eon | Eon extending from the time that oceans formed, single celled life originated, and the atmosphere was oxygenated 3.8 billion years ago, to 2.5 billion years ago. |
| Phanerozoic Eon | The most recent eon, an interval of time from 542 Ma to the present and includes the Cambrian Explosion, primitive plants, dinosaurs, and humans. |
