The tick bird hitches a ride on the back of a bison. The bison doesn't know the bird is there.

The clownfish keeps the anemone's predators away with special cells that send out an electric shock. The anemone gives the clownfish a safe home.

The epiphytes are plants that grow on other trees. The epiphytes benefit from being off of the ground because they get more sunlight. The tree isn't affected by the epiphyte.

Barnacles attach themselves to whales. Not only do the barnacles get protection from predators, but they get a free meal. As the whales swim and consume plankton, the barnacles eat the plankton that swims by. The whales don't notice the freeloaders.

Warthogs lie down when mongoose are near. The mongoose crawl on top of the warthogs and inspect the fur for ticks. The mongoose devour any tick they find. The warthogs enjoy this immensely!