All the life zones of the earth in which organisms live through a continuous interaction among them, and with their physical environment are together called as biosphere.
The biosphere is made of fundamental structural and functional units of biotic and abiotic components called as Ecosystems. The term Ecosystem was coined by Roy Clapham in 1930 and was first used by his one of colleagues Arthur Tansley in one of his publications in 1935. Ecosystem, according to these naturalists, is a dynamic complex of plants, animals and microorganisms inhabiting a particular area with their non-living counterparts interacting as a functional unit.
The Ecosystems may be of various different types such as Terrestrial Ecosystems (like Tundra, Forests, Grasslands and Deserts) and Aquatic Ecosystems. The aquatic ecosystems may be categorized into fresh water ecosystems, marine ecosystems and estuarine ecosystems.
An aquatic ecosystem
All the ecosystems of the biosphere have some well organized functions like cycling of nutrients through food chains or, operation of bio-geo- chemical cycles, and maintenance of flow of energy received by green plants through solar radiation.
The green plants utilize solar energy to carry on photosynthesis or the process of food preparation. During this process, they utilize carbon dioxide, water and minerals and release out oxygen that is again required by them in the process of respiration or the process of oxidation of food for the release of energy contained in food particles. As we know, carbon dioxide comes out in this process which is again needed during the processes of photosynthesis.
The food prepared by green plants is taken in by consumers of first order or by herbivores. The herbivores are eaten up by consumers of the second order or the carnivores. Thus food passes on in the ecosystem from consumer to consumer until the last consumer meets its death by some reason. The decomposers like fungi, bacteria, viruses, termites, and earth worms etc. decompose their dead bodies to put the nutrients back to soil.
The energy contained in the molecules of bodies of organisms escapes away into the atmosphere during this process. The nutrients or the bio-geo-chemicals put back to soil during the process of decomposition are absorbed by green plants again and the cycle goes on .Most often a number of producers and consumers remain involved in the process of consumption of food through different food chains and form a network called as food-web. Thus through cycling of materials and flow of energy the balance between the input and the out put is maintained and this balance is called as the Balance of Nature. The growth and well being of biodiversity in an ecosystem is essential for maintaining of this balance.
Key Words : life-zones, biosphere, ecosystem, photosynthesis, transfer of energy, bio-geo-chemical cycle, food-web, consumer, decomposer, herbivore, carnivore, balance in nature.