| A | B |
|---|
| Fossils are | The preserved remains or TRACES of prehistoric organisms |
| Fossils provide | PROVIDE evidence of how life changed over time (paleontology) |
| Fossils help | HELP scientists INFER how Earth's surface has changed(geomorphology) |
| Fossils show | INDICATE what past environments are like (paleoclimatology) |
| Fossils form | FORM when living things die and are buried by sediment. The sediments slowly harden into rock and preserve the shapes of the organisms or evidence of organisms. |
| Paleontologists | Scientists who study fossils |
| Sedimentary rock | Rock formed from compacted and cemented sediment; sometimes contains fossils |
| Petrified fossils | "turned to stone"; minerals replace all or part of an organism |
| Molds | Hollow areas formed when the hard part of an organism is buried in sediment |
| Casts | Minerals and sediments infiltrate hollow areas (molds) and preserve the details of an organism's structure |
| Carbon films | Delicate parts of plants and insects are preserved in sediments as the materials in the organism gasify |
| Trace fossils | Provide important evidence of the activities of ancient organisms |
| Preservation | Entire organisms have been preserved in tar |
| Fossil record | Provides evidence of the history of life on Earth and how different groups of organisms have changed over time |
| Theory | A well-tested concept that EXPLAINS a wide range of observations |
| Evolution | The gradual change in living things over long periods of time; for example paleomastodons to elephants (p.291) |
| Extinct | A type of organism that no longer lives on Earth |
| Relative age | The age of a rock layer compared to the ages of the surrounding rock layers; determined byt the ages of the rock layers above and beneath |
| Absolute age | The number of years since the formation of the rock or sample; determined through radiometric dating |
| Law of Superposition | In HORIZONTAL sedimentary rock layers |
| Extrusion | Lava that hardens on the surface (fine/no grains due to rapid cooling) Extrusions are always younger than the layers below them. |
| Intrusion | Magma that cools beneath the surface (medium or large grained due to slower cooling) intrusions are always younger than the surrounding rock layers |
| Fault | A BREAK in the Earth's crust (deformation) |
| Fold | A downward or upward bend in the Earth's crust (deformation) |
| Index fossil | Widely distributed fossil used in relative dating. Index fossils are the remains of organisms that existed only for brief periods of time. |
| Atoms | The smallest particle of a substance that retains all of the properties of that substance |
| Elements | Matter consisting of only one type of atom |
| Radioactive dating | Method of dating samples that tell the absolute age of rocks using half-lives of radioactive isotopes with in the sample. |
| Radioactive decay | The release of particles and energy by unstable elements over a period of time resulting in the formation of atoms of another element |
| Half-life | The TIME that it takes for 1/2 of the atoms in an element to decay |
| Potassium-Argon | Element used to date most ancient rocks because of its long half-life (1.3 billion years) |
| Carbon-14 | Element used to dated organic remains less than 50 |
| 4.6 billionyears | The inferred age of Earth based on the radiometric dating of moon rocks. |
| Geologic Time Scale | A time scale used by geologists that shows the life forms and geologic events in Earth's history based on major changes. |
| Eon | The largest division of geologic time |
| Era | Subdivision of eons. The current eon is divided into 3 eras. |
| Hadean eon | 4.6 - 3.9 Billion years ago (Ga) Earth is forming; earliest rocks (Precambrian) |
| Archean Eon | 4.0 - 3.5 Ga(Billion years ago) thin lithosphere formed (also Precambrian) |
| Proterozoic eon | 2.5 billion - 543 million years ago Stable continents |
| Phanerozoic Eon | The current eon; means "visible life" and refers to the Cambrian explosion where a huge variety of life forms developed |
| Paleozioc Era | 544 - 244 million years ago (Ma) "ancient life" Invertebrates |
| Mesozoic Era | 245 - 66.4 million years ago "middle life" Dinosaurs |
| Cenozoic Era | 66.4 million years ago - present "recent life" Mammals |
| Periods | Subdivisions of Eras (12 in the phanerozoic Eon) |
| Cambrian | 544 - 505 million years ago |
| Ordovician | 505-438 million years ago |
| Silurian | 438 -408 million years ago |
| Devonian | 408 -360 million years ago |
| Mississipian (Upper Carboniferous) | 360 - 320 million years ago |
| Pennsylvanian (Lower Carboniferous) | 320 - 286 million years ago |
| Permian | 286 - 245 million years ago |
| Triassic | 245 - 208 million years ago |
| Jurassic | 208 - 144 million years ago |
| Cretaceous | 144 -65 million years ago |
| Tertiary | 65 - 1.6 million years ago |
| Quaternary | 1.6 million years ago to present |
| Epochs | Subdivisions of the Cenozoic Era |
| Amphibian | Animal that lives part of life in water and part of life out of water |
| Reptiles | Animals with scaly skins and eggs with tough |
| Mass extinction | At the end of the Paleozoic period where many kinds of organisms died out (95% of ocean life) |
| Pangaea | Supercontinent that formed during the Permian period (260 Ma) |
| Vertebrate | Animal with a backbone (jawless fish were the first known) |
| Mammal | Warm blooded vertebrate that feeds its young milk |
