POLAR BEAR

Polar bears are adapted to life in the polar region, around the North Pole. Their bodies have special features that work particularly well in the polar seas. For instance, they have sharp and powerful claws for catching their food, which is mainly seals. In their own environment, they are excellent hunters; but if they had to live off the birds and squirrels in other places, they would die.
The science that studies the way that different forms of life are adapted to their particular environment is called ecology.
The first lesson of ecology, is that all life in an environment depends on other forms of life. Polar bears depend on seals, which can live only where they do because they depend on a particular kind of fish which are found in the Arctic seas.
There are certain important cycles in nature that show how plants and animals depend on each other;for example, the nitrogen cycle. Plants take nitrogen compounds from the soil and turn them into proteins. Animals eat tese proteins and return some of them to the soil as waste products, the rest when they die. Another cycle is the oxygen cycle. When we breathe, we take in oxygen, and give out carbon dioxide. Plants absorb it to make sugar compounds and in the process oxygen is produced and released to the atmosphere.
In an ideal ecological system, living things exist in balance. However, particularly where man interferes, a species may become too successful and abundant, and the balance is destroyed. For instance, the use of pesticides to kill particular plant pest may also kill predatory insects and even birds, and thus other pests are allowed to increase. Therefore, great care is needed in the use of pesticides.
Through ecology we try to restorethe balance in the ecological system, and thus save the world from devastation.