An environment is everything surrounding an organism like water, air, soil, weather, landforms, and other living things. When an animals does not have everything it needs to survive it must move. Some things that an animal might need are food, water, and space. Sometimes changes in the environment make animals change their behavior for example they might learn to eat different food. The environment might also cause a physical change over time. For example if a environment gets poisoned then animals could get birth defects.