Trophic Levels and Energy Flow Explained

TROPHIC LEVELS

• The levels of a food chain (food pyramid) are called Trophic levels.
• The various steps in a food chain at which the transfer of food (or energy) takes place are called trophic levels.
• In a food chain, each step representing an organism forms a trophic level.
• The plants are producers (or autotrophs) and constitute the first trophic level.
• They fix up the sun’s energy and make it available for consumers (or heterotrophs).
• Herbivores (which feed on plants) constitute the second trophic level.
• Carnivores (that feed on herbivores) constitute the third trophic level.
• Large carnivores or Top carnivores (which feed upon small carnivores), constitute the fourth trophic level

• When any organism dies, detritivores (like vultures, worms and crabs) eat them up.
• The rest are broken down by decomposers (mostly bacteria and fungi), and the exchange of energy continues.
• Decomposers start the cycle again.

ENERGY FLOW IS UNIDIRECTIONAL

• Ecosystem energy processes conform to the thermodynamic laws.
• Energy cannot be made or destroyed.
• Energy transformations are not perfect and energy is lost in each transformation in the form of heat.
• The flow of energy in the ecosystem is unidirectional.
• The energy enters the plants (from the sun) through photosynthesis during the making of food. This energy is then passed on from one organism to another in a food chain.
• Energy given out by the organisms as heat is lost to t used by the plants again.
• This makes the flow of energy in the ecosystem ‘unidirectional’.
• Thus the flow of energy in the ecosystem is said to be unidirectional because the energy lost as heat from the living organisms of a food chain cannot be reused by plants in photosynthesis.
• During the transfer of energy through successive trophic levels in an ecosystem, there is a loss of energy all along the path.
• No transfer of energy is 100 percent.

The energy available at each successive trophic level is 10 per cent of the previous level.

• Thus, there is a progressive decline gradual reduction) in the amount of energy available as we go from producer level to the higher trophic levels of organisms.