Any group of living and non-living things interacting with each other can be considered as an ecosystem. Within ecosystems are habitats. A habitat is the natural environment in which an organism or a group of organisms (also called a population) lives. The habitat must supply the needs of organisms, such as food, water, oxygen and minerals. If organisms’ needs are not met, they must either move to a different habitat if they can or die out. Populations within a habitat are constantly competing, preying upon and/or co-operating with others to survive.