Question

Differentiate between autogenic and allogenic succession.

Answer 1

Hint: Gradual or fairly predictable change in species composition of a given area is called ecological succession.

Complete step-by-step answer:
Difference between autogenic and allogenic succession -

S.no.	Autogenic Succession	Allogenic Succession
1.	Succession in which the species themselves bring a change in the environment during the process of succession.	Succession in which external environmental factors bring a change in the environment during succession.
2.	Changes are caused by endogenous factors.	Changes are caused by exogenous factors.
3.	Driven by biotic components of the ecosystem.	Driven by abiotic components of the ecosystem.

Additional Information:
Changes occurring during succession lead to the formation of a community that is in near equilibrium with the environment, such a community is called a climax community. Successions are of two types depending on their initial state -
Primary succession - Process starts at a place where no living organisms ever existed such as a bare rock, newly created pond or reservoir. This type of succession is slow. New fertile soil formation occurs.
Secondary succession - Process starts at places where living organisms once existed but got destroyed due to factors such as abandoned farm lands, cut forests, flooded lands, etc. No new soil formation has to occur, and the process that’s why, is faster.

Notes:
1. During succession some species colonise an area and their population becomes numerous, such a species is called seral communities.
2. The entire sequence of communities that successively change in a given area are called sere.
3. At a very early stage of earth, succession and evolution were parallel processes.
4. Life beginning on rocks is called xerarch whereas in water is called hydrarch.