| A | B |
|---|
| species | similar organisms than reproduce fertile offspring |
| variations | differences among members of the same species |
| fossil | preserved remains or traces of organisms that lived in the past |
| absolute age | the actual age of a fossil in years |
| extinct | species with no living members |
| evolution | gradual change in a species over time |
| adaptation | trait that helps an organism survive and reproduce |
| natural selection | individuals better adapted to their environment more likely to survive and reproduce |
| petrified fossil | minerals replace all or part of an organism |
| amber | tree sap in which insects become trapped and preserved |
| constructive forces | build up mountains and landmasses |
| seismic waves | waves produced by earthquakes; can be used to study Earth's interior |
| inner core | densest layer; solid iron and nickel |
| Pangaea | supercontinent formed when Earth had one giant landmass |
| plate tectonics | theory that says that Earth's lithospheric plates are in constant, slow motion |
| mid-ocean ridge | longest mountain chain on Earth |
| convergent boundary | two plates come together |
| focus | point beneath Earth's surface where actual rock break happens |
| P waves | arrive at seismograph first; can travel through liquids and solids |
| S waves | arrive at seismograph second; cannot travel through liquids |
| seismograph | records ground movements produced by seismic waves |
| aftershocks | small tremors that can cause damage in the days or months after an earthquake |
| tsunami | huge tidal wave caused by an earthquake on the ocean floor |
| volcanic belts | form along plate boundaries |
| hot spot | an area where magma from deep within the mantle melts through the crust |
