Successive replacement of one type of plant community by the other of the same areal place is known as plant succession.

Phytoplanktons form the pioneer community and a variety of trees makes the climax community of a Hydrosere.

DNA, RNA, ATP and NADP.

(a) Grazing food chain
(b) Detritus food chain

The movement of energy from producers upto top carnivores is known as food chain, i.e., in any food chain, energy flows from producers to primary consumers, then from primary consumers to secondary consumers, and finally secondary consumers to tertiary consumers. Hence, it shows linear network links.

(a) Herbivores acts as primary consumers of producers (Plants).
(b) Microconsumers decomposes the dead ,remains and excreta of plants and animals.

Gross Primary Productivity (GPP) is the total amount of food energy or organic matter or biomass produced in an ecosystem by autotrophs through the process of photosynthesis is called gross primary productivity.

Net Primary Productivity (NPP) is derived by the difference between Gross primary productivity (GPP) and respiration.
NPP = GPP - Respiration

(i) Macro consumers are herbivores, carnivores and omnivores.
(ii) Micro consumers are decomposers.

(a) Climatic factors: Light and Air.
(b) Edaphic factors: Soil and pH of soil.

A.G. Tansley (1935), who defined ecosystem as 'the system resulting from the integration of all the living and non-living factors Of the environment'.

If all producers are removed from ecosystem We tend to face the following hurdles.
(i) The Ecosystem cannot be balanced
(ii) The interlocking pattern of food chain is broken
(iii) The movement of energy transfer among the food chain cannot be established
(iv) As the green plants occupying the first trophic level (T₁) are producers - it affects majority of the food chain

There is a gradual decrease in energy transfer at successive tropic levels from producers to higher levels, hence the pyramid of energy is always upright.

Because there is no effective light penetration & predominance of heterotrophs.

Gross Primary Productivity (GPP) is the total amount of food energy or biomass produced in an ecosystem by autotrophs through the process of photosynthesis whereas Net Primary Productivity (NPP) is the proportion of energy which remains after respiration loss in the plant. When we compare GPP with NPP more energy is present in former than in latter.