| A | B |
|---|
| habitat | a place where a living thing interacts with its environment |
| population | the living things of the same kind that live in an environment. |
| community | the different populations of living things that live together in an environment. |
| ecosystem | the living things and nonliving things, such as air, water, and soil, in an environment. |
| nitrogen | a gas and one of the important nonliving things that plants and animals depend on |
| nitrogen cycle | the process of recycling nitrogen in the environment |
| succession | a series of changes in an ecosystem |
| bacteria on roots of plants | change nitrogen gas into a usable form for plants |
| decomposers | change nitogen in animal waste back to nitogen gas |
| alfalfa | one of the only plants that can take nitrogen directly from the air. |
| forest fires, clearing an area | examples of succession |
| drying of pond, ending of Ice Age | examples of slow succession |
