Ecosystem can be classified into various types on various basis. The most widely used and simple classification is on the basis of habitats.
The idea behind this classification is that each habitat exhibits a particular physical environmental condition. These conditions determine the nature and characteristics of biotic communities and therefore there are spatial variations in the biotic communities.
On this basis the ecosystem can broadly be divided as –
- (i) terrestrial ecosystems
- (ii) aquatic ecosystems
These ecosystems are further sub-divided in to various sub-types.
As the name suggests it covers the entire 29% of the land area found on the earth surface. The terrestrial ecosystems are the major source of food and raw material for human beings.
Here, the plant and animal communities are more diversified than aquatic ecosystems. Land organisms have a greater range of tolerance than the aquatic ecosystem.
But, in some cases, water is a limiting factor for terrestrial ecosystems. As far as productivity is concerned, terrestrial ecosystems are more productive than aquatic ecosystem.
The above said discussion is a comparison between terrestrial and aquatic ecosystem in general. But there are further variations in the terrestrial ecosystems in terms of physical conditions and their response to biotic communities.
Therefore, the terrestrial ecosystems are further sub-divided into various sub-types. Major sub-types are –
- (i) upland or mountain ecosystem
- (ii) low land ecosystem
- (iii) desert ecosystem etc.
These sub-systems, may be further sub-divided depending on specific purpose and objectives.
Maximum life forms are found in low lands and they keep on decreasing with the increase in height as the level of oxygen and atmospheric pressure decreases.
This ecosystem refers to the 71% of the water present on the earth surface in various forms.
Like terrestrial ecosystem, aquatic ecosystem can be further divided into various sub-types. But the major sub-divisions of this ecosystem may be fresh water, estuarine and marine. Again these ecosystems can be further subdivided into smaller ones.
If we see in terms of extent or what we call in geography in terms of scale, it ranges from open sea to small pond. The variations within the various types of aquatic ecosystem are mainly related to abiotic factors. But, there are also variations in terms of biotic communities that are living within these ecosystems.
Why are these variations?
The limiting factors in aquatic ecosystems are –
- the depth up-to which sunlight can penetrate,
- the availability of nutrients and the concentration of dissolved oxygen.
If we keep all these factors into consideration, it is found that –
- estuarine ecosystems are the most productive of aquatic ecosystems;
- in marine ecosystems, shallow continental shelves are more productive than open oceans;
- though open oceans are most extensive in areas, they are the least productive of all ecosystems like the deserts in terrestrial ecosystem.
Another aspects which is the determinants of diversity of life in aquatic ecosystem is the adaptability of organisms –
- some of the organisms exclusively live in water namely fishes;
- some of the organisms are amphibious in nature namely frogs, crocodiles, hippopotamus and variety of aquatic birds;
- within water, some organisms live only in either fresh water or saline water;
- some organisms live in both fresh water and saline water namely Hilsa fish;
- Echinoderms and Coelenterates live only in saline water and there are various types of fishes like Rohu, Catla etc found only in fresh water.
Bibliography : NIOS Geography Book