All animals depend on plants. Some animals eat plants for food. Other animals eat animals that eat the plants. An organism's patterns of behavior are related to the nature of that organism's environment, including the kinds and numbers of other organisms present, the availability of food and resources, and the physical characteristics of the environment. When the environment changes, some plants and animals survive and reproduce, and others die or move to new locations.
All organisms cause changes in the environment where they live.
Some of these changes are detrimental to themselves or other organisms, whereas others are beneficial. Humans depend on both their natural and their constructed environment. Living things perform specialized tasks in the environment. Resources include those things that we get from the living and nonliving environment to meet the needs and wants of a population. The supply of many resources is limited.