How do animals and plants depend on each other?

Not only do plants help provide oxygen, but animals rely upon plants for food and energy.  As the energy comes down from the sun, and transfers itself through the foods, and the varying creatures that eat it.  Plants also depend upon animals not only to help them reproduce, as some plants have pollen or ferns or something that sticks to an animals coat, but animals can also help rival plants grow and prosper, as it's a battle for sunlight when you're a plant.. and the fewer rivals you have.. the better off you will be.