| A | B |
|---|
| biome | A group of land ecosystems with similar climates and organisms. |
| desert | An arid region that on average receives less than 25 centimeters of rain a year. |
| canopy | A leafy roof formed by tall trees in a forest. |
| understory | A layer of shorter plants that grow in the shade of a forest canopy. |
| grassland | An area populated by grasses and other nonwoody plants. Most grasslands get 25 to 75 centimeters of rain each year. |
| savanna | A tropical grassland with clumps of trees. |
| deciduous tree | A tree that sheds its leaves and grows new ones each year. |
| coniferous tree | A tree that produces its seeds in cones and that has needle-shaped leaves. |
| tundra | A polar climate region, with short, cool summers and bitterly cold winters. |
| permafrost | permanently frozen soil found in the tundra climate region. |
| estuary | A habitat in which the fresh water of a river meets the salt water of the ocean. |
| intertidal zone | An area that stretches from the highest high-tide line on land out to the point on the continental shelf exposed by the lowest low tide. |
| neritic zone | The region of shallow ocean water over the continental shelf. |
| kelp forests | Marine ecosystem where large, brown algae called giant kelp grow. |
| coral reefs | A structure of calcite skeletons built up by coral animals in warm, shallow ocean water. |
| plankton | Tiny algae and animals that float in water and are carried by waves and currents. |
| renewable resource | A resource that is either always available or is naturally replaced in a relatively short time. |
| clear-cutting | The process of cutting down all the trees in an area at once. |
| selective cutting | The process of cutting down only some trees in an area. |
| sustainable yield | An amount of a renewable resource that can be harvested regularly without reducing the future supply. |
| fishery | An area with a large population of valuable ocean organisms. |
| aquaculture | The farming of saltwaer and freshwater organisms. |
| biodiversity | The number of different species in an area. |
| keystone species | A species that influences the survival of many others in an ecosystem. |
| extinction | The disappearance of all members of a species from Earth. |
| endangered species | A species in danger of becoming extinct in the near future. |
| threatened species | A species that could become endangered in the near future. |
| habitat destruction | The loss of a natural habitat. |
| poaching | Illegal killing or removal of wildlife from their habitats. |
| captive breeding | The mating of animals in zoos or wildlife preserves. |
