Energy flow explains how solar energy is transferred through different trophic levels of an ecosystem. The concepts of the 10% law, ecological pyramids and energy transfer are frequently asked in competitive examinations.
Correct Answer:
(A) Transfer of energy as food from one trophic level to other
The Ten Percent Law of transfer of energy from one trophic level to the next was introduced by Raymond Lindeman in 1942. According to this law, during the transfer of energy from organic food from one trophic level to the next, only about ten percent of the energy from organic matter is stored as flesh. The remaining is lost during transfer, broken down in respiration or lost to incomplete digestion by higher trophic level. When organisms are consumed, 10% of the energy in the food is fixed into flesh and is available for next trophic level (carnivores or omnivores). When a carnivore or an omnivore consume that animal, only about 10% of energy is fixed in its flesh for the higher level. Thus, at every level of the food chain (first, second, third and top level), the consumer converts only 10% of the accumulated energy into his body weight.
Ques: 2
Which of the following statement is correct?
Correct Answer:
(A) The energy flow in the biospheric ecosystem is unidirectional.
The flow of energy in the ecosystem is unidirectional (or one-directional). 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. The energy given out by the organisms as heat is lost to the environment. It does not return to be used by the plants again. This makes the flow of energy in the ecosystem ‘unidirectional’. According to the first law of thermodynamics, energy can neither be created nor be destroyed in an isolated system. According to the second law whenever energy transforms into a new form, there is evident decay in its intensity. Similarly, with increasing trophic levels availability of energy decreases in the natural ecosystem.
Ques: 3
The amount of energy during the transfer from one trophic level to another in an eco-system–
Correct Answer:
(B) Decreases
Energy is the basic force responsible for all metabolic activities. The flow of energy from producer to top consumers is called energy flow, which is unidirectional. Energy flows through the trophic levels i.e. from producers to subsequent trophic levels. This energy always flows from lower (producer) to higher (herbivore, carnivore, etc.) trophic level. There is a loss of some energy in the form of unusable heat at each trophic level so the amount of energy during the transfer from one trophic level to another decreases in an ecosystem.
Ques: 4
Consider the following statements regarding energy flow:
1. Every trophic level sees about 90% energy loss, underscoring nature’s efficiency limits.
2. Unidirectional energy flows in one direction from producers to top consumers with recycling of the energy itself.
Which of the statements given above is/are correct?
Correct Answer:
(A) 1 only
Energy Flow
Sunlight Efficiency: Despite the sun’s immense energy, only 2–10% of the Photosynthetically Active Radiation is used by plants.
Energy Loss: Every trophic level sees about 90% energy loss, underscoring nature’s efficiency limits.
Unidirectional Flow: Energy flows in one direction—from producers to top consumers—with no recycling of the energy itself.
Ques: 5
The energy flow in an ecosystem is
Correct Answer:
(B) Unidirectional
The flow of energy in an ecosystem is unidirectional, meaning it moves in one direction only. This occurs because energy is lost as heat during metabolism and other processes, and this lost energy cannot be reused by producers (like plants) for photosynthesis.