energy for activities such as feeding. Many animals convert not more than 10% of their food into their body tissues, in some herbivores, it is even less. Let us take an example of a food chain which has been worked out in some detail- one in which we are involved when we eat fish. In this chain the plant plankton on the surface of waters of sea are food producers. They trap energy from sunlight. The animal plankton feed on the microscopic plants and the fish in turn feed on the animal plankton; we are at the end of the chain when we eat the fish.

Pyramid of Energy

Food is the source of energy for organisms that are used in the growth and rebuilding the part of the body; that are constantly wearing out. The food by its nature is the chemical energy and as in stored form, it is the potential energy. There are several mechanisms in organisms for continuous absorption of materials for the production of organic material, and for the release and conversion of organic material into inorganic form. Plants absorb the minerals from the soil. They are absorbed into the plant through roots.

Photosynthesis is an essential process for the life. The energy in sunlight, carbon dioxide and the water which are needed by all living things belong to nonliving things. As a result of photosynthesis, these can be made available in a suitable form of energy the food to the world of living things the animals or consumers, only by the green plants the producers. The food chains and food webs help in the transfer of the food and energy from the producers to different consumers. Animals obtain the minerals from the plant or animal food or both. Thus the mineral matter is constantly being removed from the earth to become a part of the plant, which may become a part of animal body.

Try to identify the basic sources of various foods we eat. For example curd that we eat is processed from milk, which comes from a cow, which in turn eats grass. The grass carries out photosynthesis and prepares food. In every case, the origin of food materials can be traced back to green plants.

Once the food is eaten, its energy follows a variety of pattern through the organisms. Not all the food can be fully digested and assimilated. Hair, feathers, insect exoskeletons, cartilage and bone in animal foods, cellulose and lignin in plant foods cannot be digested by most animals. These