| A | B |
|---|
| water cycle | the continuous movement of water between Earth's surface and the air, changing from liquid to gas to liquid |
| estuary | the boundary where a freshwater ecosystem meets a saltwater ecosytem |
| condensation | the changing of a gas into a liquid |
| precipitation | any form of water that falls from the atmosphere and reaches the ground |
| watershed | area from which water is drained |
| runoff | Precipitation that flows across the land's surface or falls into rivers and streams |
| groundwater | Precipitation that seeps into the ground and is stored in tiny holes, or pores, in soil and rocks |
| carbon cycle | the continuous exchange of carbon dioxide and oxygen among living things |
| nitrogen cycle | the continuous trapping of nitrogen gas into compounds in the soil and its return to the air |
| compost | a mixture of dead plant material that can be used as fertilizer |
| extinct species | a species that has died out completely |
| endangered species | a species that is in danger of becoming extinct |
| threatened species | a species that is in danger of becoming endangered |
| succession | the process of one ecosystem changing into a new and different ecosystem |
| primary succession | the beginning of a community where few if any living things exist or where earlier communities were wiped out |
| pioneer species | the first species in an otherwise lifeless area |
| pioneer community | the first community living in a lifeless area |
| climax community | the final stage of succession in an area unless a major change happens |
| secondary succession | the beginning of a new community where an earlier community already exists |
| biome | one of the earth's large ecosystem with its own kind of climate, plants, soil, and animals |
| desert | a sandy or rocky biome with little precipitation or plant life |
| tundra | a large treeless plain in the Arctic regions where the ground is frozen all year |
| taiga | the cool forest biome of conifers in the upper Northern Hemisphere |
| tropical rainforest | a hot humid near the equator with much rainfall and a wide variety of life |
| temperate rainforest | a biome with a lot of rain and cool climate |
| deciduous forest | a forest with many kinds of trees that lose their leaves each autumn |
| grassland | a biome where grasses not trees are the main plant life |
| plankton | organisms that float on the water in aquatic ecosystems and are unable to swim |
| nekton | organisms that swim through the water in aquatic ecosystems |
| benthos | organisms that live on the bottom of aquatic ecosystems |
| intertidal zone | the shallowest part of the ocean ecosystem where the ocean floor is covered and uncovered as the tide goes in and out |
| evaporation | the change of a liquid into a gas |
