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NEET Biology Notes Organisms and Ecosystem-Ecosystem

NEET Biology Notes Organisms and Ecosystem-Ecosystem

Ecosystem

Ecosystem is a functional unit of nature, where living organisms interact among themselves and also with the surrounding physical environment.requirements through its internal fat oxidation.

Ecosystems are classified in following types:

NEET Biology Notes Organisms and Ecosystem-Ecosystem 1

The following are the components of ecosystems may be given as:

  •  Biotic Components
    It include autotrophic components (self-nourishing), heterotrophic components (depend on other) and decomposers.
  •  Abiotic Components
    Abiotic component of an ecosystem consists of non-living substances and factors.

NEET Biology Notes Organisms and Ecosystem-Ecosystem 2

Functions of Ecosystem

The major functions of any ecosystem are

  • Productivity
    The rate of biomass production is called productivity.
    Productivities are two types :
  1.  Primary productivity is expressed as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis and expressed in terms of weight (g-2) or energy (kcal m2).
  2.  Secondary productivity is the rate of formation of new organic matter by consumers. The annual net primary productivity of the whole biosphere is approximately 170 billion tons of organic matter.
  • Decomposition
    Decomposers breakdown complex organic matter into inorganic substances like carbon dioxide, water and nutrients and this process is called decomposition.

Dead plant remains such as leaves, bark, flowers ‘ and dead remains of animals, including faecal matter, constitute detritus (raw material for decomposition).
The important steps in the process of decomposition are

  • Fragmentation
  •  Leaching
  • Catabolism
  •  Humification
  • Mineralisation.
  •  Energy Flow

The flow of energy from the sun to producers and then to consumers is unidirectional.
In an ecosystem, energy as transferred in the form of food and it leads to degradation and loss of a major part of food energy as heat during metabolic activities and very small fraction becomes stored as biomass.
In nature, basically two types of food chains are recognised.
NEET Biology Notes Organisms and Ecosystem-Ecosystem 3
NEET Biology Notes Organisms and Ecosystem-Ecosystem 4

Food chains are not isolated units but are hooked together in food webs.
In an ecosystem, interlinking pattern of a number of food chains forms a web-like arrangement known as a
food web.

  •  Nutrient Cycling

The nutrients are never lost from an ecosystem but are recycled again indefintely. The amount of nutrients,
i. e. carbon, nitrogen, phosphorus calcium, etc., present in soil at any given time is called as standing state. Environmental factors like temperature, soil nature and moisture can regulate the rate of release of nutrients.

Nutrient cycles are of two types :

Gaseous cycle exists in the atmosphere, e.g. carbon cycle and nitrogen cycle.

Carbon Cycle

  •  Carbon cycle occurs through atmosphere, oceans and living and dead organisms.
  •  About 71% of global carbon is found as dissolved form in the ocean. About 4 x 1013 kg of carbon is fixed in the biosphere through photosynthesis annually.
  •  Carbon dioxide is also returned to the atmosphere through
  1.  Burning of fossil fuels, fuel wood and organic debris
  2.  Forest fires .
  3. Volcanic acitivity

Sedimentary cycle exists on the earth’s crust, e.g. phosphorus cycle and sulphur cycle.

Phosphorus Cycle

  • The natural reservoir of phosphorus is rock in the form of phosphates. Phosphates enter the plants through their roots and than the food chain.
  •  The organic wastes and dead organisms are decomposed by the phosphate-solubilising bacteria, which release phosphorus back in the soil.
  • The atmospheric input of phosphorus through rainfall or gaseous exchange of phosphorus betwen organisms and environment is negligible.

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