Category Biology

                   Coral reefs are the marine equivalent of rainforests. They are home to huge numbers of a great variety of animals. Unlike some other habitats, few plants grow on coral reefs because fish and sea snails graze them. Ocean currents carry most of the food to the reef. Plankton is the basic food that powers the whole reef system. The small animals that feed on plankton are eaten by large crustaceans and fish, and so on up the food chain to predators such as sharks.

                 If a coral reef continues to grow it may begin to rise out of the water, becoming a coral island. The sea helps to break up the coral growths and pile them up. Creatures such as calcifying algae cement the pieces together to form a solid structure. If soil lodges in the coral vegetation often begins to grow on the surface. Many of the Pacific islands were formed in this way.

                         Temperate forests contain far more varieties of trees and shrubs than are found in conifer forests. Because the shade in these forests is not so great, there is far more undergrowth and larger clearings between the trees. During the lifetime of a tree such as the oak, large branches fall off and rot on the forest floor, providing a rich habitat for fungi and small animals. Other fungi live naturally in association with tree roots, and their mushrooms are eaten by mice and squirrels. Foxes are common predators in temperate forests. Deer graze in the clearings and feed on young trees. Many types of small seed-eating bird live in temperate forests, hunted by predators such as hawks.

                    Tropical rainforests contain the most varied mixtures of animals and plants of any habitat on the Earth. They contain large and small predators and a bewildering variety of birds. All these animals are supported by huge numbers of trees that produce fruit to feed them and their prey all year round. Because there is no true winter in tropical rainforests, there is no need for the cycle of eating and storing food that takes place in cooler climates.

                         Conifer forests cover huge areas of cool parts of the world. They are not rich in plant life apart from the trees, because the deep shade of the forested areas prevents most other plants from growing.

                         Various kinds of squirrel, burrowing rodents that feed on fallen cones, and many types of bird inhabit conifer forests. Eagles, hawks and owls prey on the small rodents. Deer graze on the bark of young trees, and the huge moose lives in wet areas, paddling around the edges of lakes and streams and feeding on water plants.

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                  Tundra is the cold, partly frozen region near the North Pole. It is covered with grasses and other low-growing plants, including the lichen known as reindeer moss. Many familiar trees such as willows and birches live in the tundra too, but they are stunted and low growing. Despite the cold, the tundra is covered with flowers in the spring, and huge numbers of flies pollinate them. Mosquitoes are present in vast numbers, biting the mammals that live in this region.