In a rainforest, the plants that can reach the sunlight in the canopy survive.

Spider crabs live in shallow areas of the ocean floor, and greenish-brown algae lives on the crabs' backs, making the crabs blend in with their environment. The algae gets a good place to live, and the crab gets camouflage.

Heartworms can be found in dogs, whose adults reside in the right side of the heart.

Barnacles attach to the sides of whales. Whales don’t seem to care, but the barnacles find a habitat rich in excess nutrients.

Large aphids (insects) defend feeding sites on cottonwood leaves by kicking and shoving smaller aphids from better sites.

Mosquito: Females ingest blood for the protein.

Fleas harm their hosts, such as dogs, by biting their skin, sucking their blood, and causing them to itch. The fleas, in turn, get food and a warm home.

A Salamander captures an insect with it’s sticky tongue.

Remora sharks hitch a ride on larger animals, usually whales. When food floats away from the whale’s mouth, the remora unhitches itself and collects the scraps of food floating by.

A spider catches a fly it it’s spider web.

Bees fly from flower to flower gathering nectar, which they make into food. The bees get some pollen on their bodies, and when they land in the next flower, some of the pollen from the first one rubs off, pollinating* the plant.

A barn own captures a mouse during a night flight.

Plants consume nitrogen by absorbing it into their roots, making nitrogen unavailable to other nearby plants.

As cattle graze on the field, they cause movements that stir up various insects. As the insects are stirred up, cattle egrets following the livestock catch and feed upon the insects.

Oxpeckers land on rhinos or zebras and eat ticks and other parasites that live on their skin. The oxpeckers get food and the beasts get pest control.

A spider uses the antlers of a gazelle as a home for it’s web. As long as the gazelle doesn’t run too fast, the spider’s web will survive and catch food.

Certain wasp varieties lay their eggs on the backs of tomato hornworm caterpillars. When the larva hatch they slowly consume the caterpillar in order to gain nutrients.