Page 5 - Lesson note-Ecosytem

exceeds that of phytoplankton.

c) Pyramids of energy- that give s graphic representation of amount of energy trapped by

different trophic levels per unit area. Pyramid of energy is always upright, can never be
inverted, because when energy flows from a particular trophic level to the next trophic level,

some energy is always lost as heat at each step e.g in feeding, digestion, assimilation and

respiration.

Ecological Succession

The gradual and fairly predictable change in species composition of a given area is called

ecological succession. During succession some species colonise an area and their population
becomes more numerous whereas population of other species decline and even disappear.

· Orderly and sequential change that leads to a community that is near equilibrium is called

climax community.

· The entire sequence of communities that successively changes in a given area is called sere

and individual transitional communities are termed seral stage or seral communities.

Ecoloical Succession : Primary sucsesion, Secondary Succession

· Primary succession starts where no organism are there. For example bare rocks, cooled

volcano etc. Secondary succession occurs in the area where the living organisms have lost
due to certain regions like forest fire. Earthquake etc.

Succession of Plants

On the basis of nature of habitat, succession of plants can be grouped as-

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