All the living and nonliving things in an area interacting with each other is a(n) ecosystem. The study of how living things and their environment interact is called ecology. The nonliving parts of an ecosystem are abiotic factors. All living things require water to stay alive. Living things also need minerals such as iron and calcium. Algae and plants must have sunlight to make food. They also need carbon dioxide. Animals require oxygen to produce the energy their bodies need.