A mosquito feeding off of a human.

A bird lives in a tree.

Bacteria in our stomach.

Barnacles living on a whale.

A mountain lion eats a rabbit.

A lizards catches and eats an insect.

A flea feeds on a dog.

A cowbird eats the ticks off of a cow’s back.

Mistletoe lives on and feeds off of a tree. The tree is harmed, but not immediately.

Bacteria living at the roots of a tree: the tree gains nutrients, but the bacteria gain nothing from the tree.

A cow eats grass.

Lichen is a protist and an algae living together. The algae retains moisture that both need to live. The protist produces nutrients for both.

A dung beetle and the larger animals that provide the dung. (A dung beetle gathers the dung [manure] of other animals and rolls it into a ball to move it. The beetle feeds on the ball, making it a decomposer.)

As a farmer is plowing a field, birds land and eat worms and other insects that are exposed by the plowing.