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Principle of energy flow| Principle of Trophic level | Principle of ecology UPSC | Environmental Geography | Physical geography

Energy flow in the ecosystem:

Energy flow in the ecosystem is a basic principle of ecology. Energy is needed for the biotic components of the ecosystem. 

Energy flow in the ecosystem gets transferred through the food chain. There are two types of energy transfer( food chain) in the ecosystem;

  • Grazing Food Chain and Food Web
  • Detritus Food Chain


Grazing Food Chain and Food web

  • Energy for the grazing food chain is directly obtained from Sun radiant energy. 
  • Only 50 % of the Incident ray of the Sun is Photosynthetically Active Radiation( PAR).
  • Plants and photosynthetic bacteria( autotrophs) can fix Sun's radiant energy to make food from simple inorganic substances such as carbon dioxide, water, and nutrients. 
  • Vegetations are able to capture only 2-10 % of PAR and this energy gets transferred across the trophic level and sustains the entire biosphere.
  • Based on the feeding relationship and nutrition requirement, organisms occupying a specific place in the food chain is known as a trophic level. 
Grazing Food Chain and Food web UPSC


The following are levels of trophic levels in the biosphere;

  • First trophic level: Producer
    • For example, Phytoplankton, grass, trees, photosynthesized bacteria.
  • Second trophic level: Herbivores or primary consumers.
    • For example, Zooplankton, grasshopper, cow
  • Third trophic level: Carnivores or secondary consumer
    • For example, Birds, fishes, and wolfs
  • Fourth Tropic level: Top Carnivores or tertiary consumers.
    • For example, Man and Lion

Food chain vs Food web;

  • The food chain is a linear flow of energy from one organism to another organism whereas the food web is termed as the combination of many different food chains and a relationship exists between more than one organism for energy needs.
  • The food chain provides only one alternative of food to each organism whereas the food web provides more than one source of food for the organism and it increases the chance of survival.


Detritus Food Chain:

The Detritus food chain starts from the decomposition of the dead organism by the decomposer.

The detritus comprises dead plants or animal remains are the raw material for decomposition.

Decomposer such as earthworm breaks down a complex organic substance into simple inorganic substance such as carbon dioxide,  water, and nutrients; this process is called decomposition.

Detritus Food Chain UPSC


 The following are the important steps of the decomposition process;

  • Fragmentation
  • Leaching
  • Catabolism
  • Humification 
  • Mineralization

Fragmentation:

  • Breaking down detritus into smaller particles by Detritivores (earthworms) is called Fragmentation.

Catabolism:

  • Bacterial and fungal enzymes change degraded detritus to simple inorganic substances; this process is called Catabolism;

Humification:

  • Accumulation of dark-colored organic and inorganic degraded substances is called humification.

Mineralization:

  • The hummus is further degraded by some bacteria and an inorganic substance is released; this process is known as mineralization.
Energy Pyramid:
  • Energy Pyramid is a graphical representation of energy flow and quantity of energy in each trophic level.
  • The base of the energy pyramid indicates the energy produced by producers or autotrophs.
  • The top of the pyramid comprises apex predators.
The following diagram explains the Energy pyramid.

Energy Pyramid UPSC


The following are principles of energy flow;

  • The principle of trophic level and the principle of energy flow is generally the same because both work on the food chain and food web principle.
  • Unidirectional flow of energy from the sun to producer to consumers.
  • A constant supply of energy from the sun is needed for the sustainability of the ecosystem.
  • The food web or chain is formed because of the interdependency of the organism.
  • No energy that is trapped in an organism remains in it forever; either the organism passes the energy to another organism or it dies; the death of the organism is the beginning of the detritus food chain or web.
  • Amount of energy decrease at the successive trophic level;
  • Transfer of energy fallow the 10 % law; only 10 % of the energy is transferred to each trophic level.
  • The food chain is usually short because the loss of respiration energy is more at the higher trophic level.
  • An organism at the higher trophic level is generally more efficient in using energy.

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