| A | B |
|---|
| species | a group of similar organisms that mate & produce fertile offspring |
| adaptation | a trait that helps an organism survive and reproduce |
| natural selection | individuals that are better adapted to their environment survive and reproduce better than others |
| evolution | the gradual accumulation of helpful traits over many generations |
| fossil | the preserved remains or traces of an organism that lived in the past |
| fossil record | the collection of the millions of fossils found |
| extinct | no members of that species are still alive |
| homologous structures | similar structures that related species have inherited from a common ancestor |
| branching tree | a diagram that shows how scientists think different groups of organisms are related |
| igneous rock | forms when molten material cools and hardens below or on the Earth's surface |
| sedimentary rock | forms when particles of other rocks or the remains of plants and animals are pressed and cemented together |
| metamorphic rock | formed when an existing rock is changed by heat, pressure, or chemical reactions |
| petrified fossils | fossils in which minerals replace all or part of an organism |
| mold fossil | a hollow area in sediment in the shapre of an organism |
| cast fossil | a copy of the shape of an organism |
| paleontologists | scientists who study fossils |
| carbon film fossil | a thin coating of carbon on rock |
| trace fossils | fossil that shows evidence of activities of ancient organisms |
| relative age | age of a rock that is compared to ages of other rocks |
| absolute age | the number of years since the rock formed |
| extrusion | lava that hardens on the surface |
| intrusion | magma that pushes into existing rocks |
| fault | a break in the Earth's crust |
| index fossil | a fossil that is found in many locations but in only one time period (one rock layer) |
| geologic time scale | a record of the life forms and geologic events in Earth's history |
| mass extinction | many types of living things became extinct at the same time |
| Pangaea | a supercontinent (all of Earth's continents had moved together) |
