Earth phenomena are of two types. They are the living and the non-living. In the two, there are several ecosystems. In the living,there are seven ecosystems and, in the non-living, there are four ecosystems. How an individual organism of the living organisms interacts with its environment can be understood through a study of biogeography.
It is almost 1000 million years since life forms appeared, on the surface of the earth. The first organisms began their lives in the seas. Land organisms appeared soon afterwards. In course of time, almost 3 million (3 x 106 ) plants, animals and micro organisms came into existence. Presently, 1.0 million animals and 0.5 million plants have been identified and classified. There are as yet several organisms that have not been classified. These living organisms are unevenly distributed on the surface of the earth. Each of the ecosystems consists of its own flora and fauna. If these were not living on the earth, the earth would have been a sterile planet.
Land, water and winds are the three natural systems of spheres.
They are of solid, liquid and gaseous forms. They may be called the non-living. Besides these, there is a fourth sphere consisting of the flora and fauna. This is called the biosphere. This may be alternatively called the living systems. Between the living and the non-living systems, there are various interactions. Several environmental changes occur on the earth in response to these interactions.
'Place' is an important concept in geography. 'People' are the most characteristic component of that place. Hence, of all ecosystems, human ecosystems have greater importance and value. It is for this reason this ecosystem is shown at the top of all the ecosystems. All the eleven ecosystems of the living things in a reverse order. The ecosystems 1-4 of the non-living things may be studied under physical geography.
The millions of plants on this earth form the very basis of survival of all other life forms. It was primarily the plant life of several million years ago that generated the oxygen in the atmosphere for our survival. It is held among the botanists that the destruction of one plant species is like extinguishing 30 animal species. There are innumerable plant species that alter their lives in accordance with the environments around them. For example, there are luxuriously growing plants from the deserts to the Tundra of the poles.
The development of vegetation has a range of xerophytic plants of the desert wastes to the abundantly evergreen trees of the tropics. With the human intervention, the vegetation has been affected in several places. Of the total land area of the world, 30 per cent is occupied by the forests. These forests are a fundamental cause for biological activities, biomass and plant nutrition. They also determine the nature and magnitude of the bio-geo-chemical cycles such as the carbon, nitrogen and oxygen cycles. Further, they determine the temperature, rainfall and other climatic elements of the earth.
The plant and animal communities of the biosphere living in a particular territory is called the 'biomes'. These biomes adapt themselves to the prevailing environmental conditions of the surroundings. The biomes help us with a clear understanding that we require of the relationships among the ecosystems. Let us now see the interactions and relationships among the climate, soil, vegetation, animals and humankind. Based on their structural characteristics, the biomes can be classified, as follows: -
1. FOREST BIOMES
a. Coniferous forests
c. Tropical forests
2. GRASSLAND BIOMES
a. Temperate grasslands
3. DESERT BIOMES
a. Cold deserts
4. MOUNTAIN BIOMES