The flow of energy in an ecosystem is
- A.unidirectional
- B.cyclic, like the flow of nutrients
- C.from consumers to producers
- D.unchanged at every trophic level
Correct answer
Explanation
The correct answer is A, unidirectional. Energy enters an ecosystem as sunlight, is fixed by green plants, and then moves from producers to herbivores, to carnivores and finally to decomposers. At every step a large part of it is lost to the surroundings as heat, and none of it returns to the Sun, so the flow runs in one direction only.
Option B confuses energy with nutrients. Carbon, nitrogen and other nutrients do move in cycles, because decomposers release them from dead matter for plants to use again. Option C reverses the direction: consumers depend on producers, never the other way round. Option D contradicts the ten per cent law, since only about a tenth of the energy at one level reaches the next. A short way to remember it: nutrients cycle, energy flows.
Read the full article: Ecosystem and Food Chains: Components, Levels and Pyramids
Practice Questions
View allThe term ecosystem was coined by which scientist?
- A.A. G. Tansley
- B.Charles Darwin
- C.Raymond Lindeman
- D.Charles Elton
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The British botanist Arthur George Tansley used the word ecosystem in 1935 for a unit in which living organisms and their non-living surroundings are treated together as one system exchanging energy and matter.
Read the full explanation →In a food chain, green plants are called
- A.Producers
- B.Primary consumers
- C.Decomposers
- D.Secondary consumers
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Green plants make their own food from carbon dioxide and water by photosynthesis, using the energy of sunlight, so they are also called autotrophs.
Read the full explanation →The ten per cent law of energy transfer in a food chain was given by
- A.A. G. Tansley
- B.Raymond Lindeman
- C.Odum
- D.Ernst Haeckel
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It says that only about ten per cent of the energy present at one trophic level is passed on to the next, since the rest is used in respiration and other life processes and is lost to the surroundings as heat.
Read the full explanation →Which of the following ecological pyramids is always upright?
- A.Pyramid of numbers
- B.Pyramid of biomass
- C.Pyramid of energy
- D.All three are always upright
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Energy is lost as heat at every transfer from one trophic level to the next, so a higher level can never hold more energy than the level below it.
Read the full explanation →Bacteria and fungi that break down dead plants and animals are known as
- A.Producers
- B.Decomposers
- C.Herbivores
- D.Omnivores
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They feed on dead bodies, fallen leaves and waste matter, break the complex organic substances into simple ones and release nutrients back into the soil, water and air, where plants can take them up again.
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