Different species compete to survive and breed. The size of a predator population depends on the size of the prey population, and the reverse is true as well. Mutualism benefits both species involved in the relationship, but parasitism only benefits the parasite, not the host.

Competition

Habitats have limited amounts of the resources needed by living organisms. Organisms must compete with others in order to get enough of these resources to survive. If they are unsuccessful and cannot move to another habitat, they will die.

ANIMALS COMPETE FOR:

Water

Space

Food

PLANTS COMPETE FOR:

Light

Water 

Space

Mineral Salts

Predators are animals that eat other animals. Prey are the animals that get eaten. The size of the predator population and prey population depend on each other.

MUTUALISM

Some organisms rely on the presence of organisms of a different species. For example, oxpecker birds eat ticks and larvae infesting the skin of buffalo and other large animals. For this reason oxpeckers are called a cleaner species. This is an example of mutualism - both species benefit from the arrangement.

PARASITISM

Parasites are organisms that live on or in a host organism. The parasite benefits from this arrangement, but the host suffers as a result. Fleas are parasites. They live on the skin of other animals and **** their blood. This feeds the flea but weakens the host.