The tropical rainforest can be thought of as a superorganism - a living, dynamic entity in its own right.

All of the living things in the tropical rainforest have been molded by the same climatic regime, and each is more or less dependent on the others.

Tropical rainforests have two outstanding characteristics.

First, the total bulk of plant and animal matter supported by each square yard is enormous - many times larger than on any other square yard of the earth's surface.

Second, the diversity of animal and plant forms is far higher than in any other habitat.

These characteristics make the tropical rainforest unique.

The total mass of living matter and the enormous diversity of life produce a wild profusion of specific niches for animals and plants.

The floor of the tropical rainforest is virtually bare of plants, and the gloom is relieved only by the occasional shafts of sunlight that penetrate the canopy.

At higher levels, there is more light, more vegetation and more animal life.

In this respect, the layered structure of the tropical rainforest is similar to that of the sea-in both, life is concentrated in the upper layers.

While many animals in the tropical rainforest feed on and live in the canopy and understory, others feed on the fruits, nuts and leaves that fall to the floor.

Although the tropical rainforest is layered, the layers are not strictly defined and the boundary between one layer and the next is not always distinct.

Most plants do have a characteristic habitat-although many must grow through other levels to reach their mature habitat-but this is not always true of animals. For example, insectivorous birds forage high in the canopy one moment and on the floor the next.

However, many creatures are highly adapted to life in a particular layer or habitat and are seldom found outside it. The three-toed sloth is so well adapted to life in the trees that it can no longer walk on the ground.

Generally, animals with varied diets can be found in a number of places in the rainforest. However, those animals with very specialized diets can only live in places where their food can be found.