14.Ecosystems and Energy flow

1.      An ecosystem is a self-regulatory and self-sustaining structural and functional unit of nature (biosphere).

2.       Ecosystem contains both biotic and abiotic components.

3.      Biotic components interact with each other and also with the surrounding environment.

4.      Ecosystem term is conined by Tansley (1935).

5.      Ecosystems varies  in size from a small pond to large oceans or small farmland to village.

6.       Entire biosphere can be considered as one global ecosystem, made up of many local ecosystems. Since the earth ecosystem is too big and more  complex .

7.      Ecosystem is divided into two basic categories, -

A. terrestrial ecosystems

B. Aquatic ecosystems.

8.      Forest, grassland and desert are the types of terrestrial ecosystems .  

9.      lakes, wetlands, rivers and estuaries are the types of aquatic ecosystems.

10.  The ecosystems can also be classified as-

A. Natural ecosystems

B.  Artificial ecosystems.

11.  Natural ecosystems do not require any human inputs, in other words they are self-sustainable.

12.  Artificial ecosystems e.g. a farm land, a fish tank or even a large pond used for rearing fish, require constant input in terms of energy or materials.

Ecosystem:

Structure and Function:

Biotic and abiotic components differ as the locations vary in space and time. The variation due to space results in spatial pattern. There are two types of spatial patterns. –

1.  Stratification

2.  Zonation.

1.Stratification- Vertical distribution of different species of plants and animals occupying different levels, is known as stratification.

For example, trees occupy top vertical strata or layer of a forest, shrubs the second and herbs and grasses occupy the bottom layer. Similar stratification is also observed in the open seas as epipelagic, meso-pelagic, bathy-pelagic and benthic zones.

2.  Zonation -Horizontal distribution of plants and animals on land or in water, is called zonation.

Zonation is observed in aquatic (wetlands) as well as terrestrial ecosystems, but it is easily seen at the junction of the two. Edges of a large lake or beach show pronounced zonation in the form of Inter-tidal, Littoral, Sub-littoral zones.