For example, humans have distinct structures of the body for walking, holding, seeing, and talking. Different substances can damage the body and how it functions. Students should understand that some substances such as prescription drugs can be beneficial but that any substance can be harmful. The human body is supported and protected by various body systems. 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.