In this topic you will learn about how living and nonliving things in an area interact with each other.

Living things and nonliving things interact in an ecosystem. An ecosystem is all the living and nonliving things in an area interacting with each other. Ecology is the study of how all these things interact in order to survive.

The nonliving parts of an ecosystem are the ecosystem's abiotic factors. All living things need certain nonliving things to survive. Abiotic factors include water, minerals, sunlight, air, climate, and soil. All organisms need water. Their bodies are 50 to 95 percent water. The processes that keep living things alive, such as photosynthesis and respiration, can take place only in the presence of water. Living things need minerals such as phosphorous, calcium, and iron. Some living things, like plants and algae, need sunlight to make food. Animals need oxygen to produce energy for their bodies. Plants and algae need carbon dioxide..

Organisms—plants, animals, fungi, protists, and bacteria—make up the biotic factors, or living parts, of an ecosystem. Each organism contributes something to the others in the ecosystem. Plants and algae are called producers. They produce oxygen and food that animals need. Animals are consumers. Animals eat either plants or other animals that eat plants. Fungi and bacteria are decomposers. They decompose, or break down, dead plants or animals.

All the organisms of a species living in the same area make up a population. Scientists want to know how populations interact. They want to know which animals prey on others, which animals eat plants, and which insects eat crops. Scientists have to study the interactions of all the populations in an area. All the populations living in an area make up a community.

The place where a population lives is called its habitat. Each species in an ecosystem also has a role or place in the activities of its community. The role of an organism in the community is its niche. A species' niche includes many factors. It includes what a species eats and what eats that species. It includes the kind of environment the species needs to live in. It even includes whether the species is active by day or by night.

The world is a place full of changes. This makes habitats change. A good habitat for a certain organism at one time may be a threatening one at another time. Animals may be adapted to changes in their habitats in different ways.