| Term | Definition |
|---|
| What is a fossil? | the preserved remains or traces of an organism |
| The process by which all the different kinds of living things have changed over long periods of time is called | Evolution |
| How do fossils form? | Living things die and their remains are buried by sediments |
| A fossil formed when minerals replace all or part of an organism is called | petrified fossil |
| Which type of fossil can provide clues about the activities of ancient organisms? | trace fossils |
| The fossil record shows that life on Earth has changed over time. For example, paleontologists have found that older rocks contain fossils of | organisms that are simpler than those alive today |
| The fossils of organisms that were widely distributed but only lived during a short period of time are called | Index fossils |
| The relative age of a rock is | its age compared to the age of other rocks |
| The law of superposition states that, in horizontal layers of sedimentary rock, each layer is | older than the layer above it and younger than the layer below it |
| Radioactive dating enables geologists to determine | the absolute age of rocks |
| Radioactive decay occurs when atoms of an unstable element | break down to form atoms of another element |
| Radioactive dating works best with what type of rocks? | Igneous rocks |
| The geologic time scale is a record of | the life forms and geologic events in Earth's history |
| Paleozoic, Mesozoic and Cenozoic arre divisions in the geologic time scale called | eras |
| The Mesozoic Era is divided into the Triassic, the Jurassic and the Cretateous. These divisions are called | periods |
| How did Earth change about 2.5 billion years ago when some organisms began using photosynthesis to make food? | The amount of oxygen in the atmosphere increased. |
| Precambrian time, which includes most of Earth's history, began with | Earth forming from a mass of dust and gas. |
| The Cenozoic Era is often called the Age of | Mammals |
| A place where an old eroded surface is in contact with a newer rock layer is called | intrusion |
| A type of organism that no longer exists on Earth is said to be | extinct |
| In which type of fossil might you find the remains of an insect preserved with little or no change? | fossil in amber |
| What do most scientists think caused the mass extinction of dinosaurs and other organisms at the end of the Cretaceous Period? | An object from space struck earth |
| During the Cambrian Explosion that began the Paleozoic Era, the many new forms of life that evolved | were invertebrates that lived in the sea |
| During the Devonian period, animals that could live on land began to evolve. These animals still spent part of their lives in the water. What were these animals called? | amphibians |
| Earth's atmosphere, oceans, and continents began to form during the first several hundred million years of | Precambrian Time |
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