The major reservoir of carbon on Earth is . (Producers/Earthworm/Ocean)

1. Introduction to Biosphere and Ecosystem:

(i) Biosphere is the largest and most nearly self-sufficient biological system and can also be called the ecosphere.

(ii) Ecosystem is a community of living organisms and the physical environment, interacting and exchanging materials.

(iii) Ecosystem is recognised as self-regulating and self-sustaining landscape units.

(iv) Major regional ecological community of plants and animals extending over large natural areas is recognised as a biome.

2. Components of Ecosystem:

(i) Abiotic and biotic components constantly interact, bringing forth structural and functional changes in the biosphere.

(ii) Ecosystem has two significant components, biotic and abiotic.

(iii) Biotic components include primary producers, consumers, and decomposers.

(iv) Abiotic components are physical factors such as climatic, edaphic, and topographic.

3. Structural and Functional Components of Ecosystem:

(i) The functional aspects of the ecosystem are related to energy flow through various trophic levels.

(ii) The rate of the amount of energy accumulated at each trophic level is termed productivity.

(iii) Organisms occupy a specific place in the food chain based on their sources of food, and this place is called a trophic level.

(iv) There are three main trophic levels—primary producers, consumers, and decomposers.

(v)The sequence of living organisms involving transfer of food energy from producers through a series of organisms with repeated eating and being eaten is called a food chain.

(vi) The complex of the interrelated food chain is called a food web.

(vii) A food web opens up several alternate pathways for the flow of food energy, maintaining equilibrium for the stability of the ecosystem.

4. Ecological Pyramid:

(i) Ecological pyramid is a graphic representation illustrating the relations of the number, biomass, and energy in an ecosystem.

(ii) The shape of the pyramid of biomass and number may differ in varied ecosystems, but the pyramid of energy is always upright.

(iii) The pyramid of energy is always upright because the flow of energy is unidirectional from the producer to the consumer level.

5. Energy Flow:

(i) Green plants convert radiant energy to chemical energy displaying energy conservation. The transfer of chemical energy (food energy) through trophic levels with loss of energy shows entropy.

(ii) The rate at which organic matter is synthesised by green plants in a unit area in a given time is called primary productivity.

(iii) There are two components of primary productivity— gross primary productivity and net primary productivity.

(iv) Maximum primary productivity occurs in coral reefs, and the minimum productivity has been recorded for desert and arctic regions.

(v) The movement of nutrient elements through the various components of an ecosystem is called nutrient cycling or biogeochemical cycles.

(vi) There are two biogeochemical cycles; gaseous and sedimentary.

(vii) Gaseous cycles like the Nitrogen cycle, Carbon cycle, Hydrogen cycle, and Oxygen cycle. They include non-mineral chemicals.

(viii) Sedimentary cycles like the Phosphorous and Sulphur cycle. They include mineral chemicals.

6. Ecological Succession:

(i) Ecological succession is the habitat colonization resulting from orderly and sequential changes corresponding to the physical environment.

(ii) The climax community is self-perpetuating and is in equilibrium with the physical habitat. It is also an index of the climate of an area.