Relationships between animals; animals and plants

Animals cannot live without plants: plants release oxygen and give animals food and shelter. Birds build nests in branches and mammals live in hollows. Plants also need animals. Bees and butterflies pollinate flowers. Animals spread seeds: a bird that eats fruit carries the seeds far away, spiny seeds stick to fur and feathers, and a squirrel hides nuts and forgets some. Wind (dandelion, maple) and water (coconut) also spread seeds. Tiny soil organisms recycle animal droppings and dead remains into mineral salts for plants. Sometimes the link is very close: in tropical America the acacia gives ants a home in its thorns and the ants defend it from plant-eaters. Some plants, like the Venus flytrap, catch and digest insects, and the sea slug Elysia gains energy from sunlight using algae it has eaten.