Ecosystem can be classified into various types on various bases.
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 eco-system can broadly be divided as
 terrestrial ecosystems and
 aquatic ecosystems.
 Terrestrial Ecosystems
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 Eco-systems.
Land organisms have a greater range of tolerance than the aquatic ecosystem.
But, in some cases, water is a limiting factor for terrestrial ecosystems.
Terrestrial ecosystems are more productive than aquatic ecosystem.
The terrestrial Eco-systems are further sub-divided into various sub-types.
Major sub-types are
— upland or mountain Eco-system
— low land Eco-system
— desert Eco-system 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.
 Aquatic Eco-system
This ecosystem refers to the 71% of the water present on the earth surface in various forms.
Like terrestrial Eco-system, 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.
The variations within the various types of aquatic ecosystem are mainly related to abiotic factors.
It is found that estuarine ecosystems are the most productive of aquatic eco-systems.
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 aspect which is the determinant of diversity of life in aquatic ecosystem is the adaptability of organisms.
Some of the organisms exclusively live in water namely fishes whereas some of the organisms are amphibious in nature.
Some of the important amphibians are frogs, crocodiles, hippopotamus and variety of aquatic birds.
Again within water, some organisms live only in either fresh water or saline water and some organisms live in both fresh water and saline water.
Echinoderms and Coelenterates live only in saline water and there are various types of fishes like Rohu, Catla etc found only in fresh water.