| Term | Definition |
| evaporation | the process in which a liquid changes into a gas |
| condensation | the process in which a gas changes into a liquid |
| precipitation | any form of water that falls to Earth (rain, snow, sleet, hail) |
| water cycle | the continuous movement of water between Earth’s surface and the atmosphere |
| carbon cycle | shows the continuous transfer of carbon between the atmosphere and living things |
| nitrogen cycle | shows the way nitrogen moves between the air, soil, plants, and animals |
| biome | one of Earth’s large ecosystem, with its own kind of climate, soil, plants, and animals |
| grassland | a biome where grasses, not trees, are the main plant life (prairie is one type) |
| taiga | a cool forest biome of conifers in the upper Northern Hemisphere (coniferous forest) |
| tundra | large, treeless plain in the arctic region where the ground is frozen all year |
| desert | a sandy or rocky biome with little precipitation and little plant life |
| deciduous forest | a forest biome with many kinds of trees that lose their leaves each autumn |
| tropical rain forest | a hot biome near the equator, with much rainfall and a wide variety of life |
| ecological succession | the gradual replacement of one community by another |
| pioneer species | the first species living in an otherwise lifeless area |
| pioneer community | the first community thriving in a once lifeless area |
| climax community | the final stage of succession in an area, unless a major change happens |
