Question

"The energy flow in the ecosystem follows the second law of thermodynamics". Explain.

Accepted Answer

The second law of thermodynamics explains the entropy. According to this, during energy exchange, no energy enters or leaves the system, the potential energy of that system will always be less than that of the initial state. The ten percent law given by Lindemann states that only 10% of the total energy is passed on from one trophic level to the other and 90% will be lost in form of heat, respiration, or decomposition. The autotrophs receive only 2-10% of the total sunrays (photosynthetically active radiations) that fall on plants.

It is used by them in the process of photosynthesis and only 10% of this energy is passed on to the next trophic level i.e., to the second trophic level (herbivores), out of which another 90% is lost and the remaining is passed on to the third trophic level (secondary consumers) and so on.

As we move higher up in the food chain, the amount of energy diminishes to a level at which it cannot sustain any trophic level. Thus, we can say that the energy flow in an ecosystem is following the second law of thermodynamics. This is the reason why there are only a few trophic levels in any sustainable ecosystem.

NCERT Solutions for Chapter: Ecosystem, Exercise 4: LONG ANSWER TYPE QUESTIONS

NCERT Biology Solutions for Exercise - NCERT Solutions for Chapter: Ecosystem, Exercise 4: LONG ANSWER TYPE QUESTIONS

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