Which of the following correctly states a difference between the grazing food chain (GFC) and the detritus food chain (DFC)?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → GFC begins with producers, while DFC begins with dead organic matter.
Food chains in an ecosystem are of two kinds. The grazing food chain (GFC) starts from living green plants, the producers, which are eaten by herbivores and then by carnivores. The detritus food chain (DFC) starts from dead organic matter and is run mainly by decomposers such as fungi and bacteria.
Option (1) GFC begins with producers, while DFC begins with dead organic matter. — Correct. This is the basic difference between the two chains: the GFC begins with producers, and the DFC begins with dead organic matter (detritus).
Option (2) GFC begins with dead organic matter, while DFC begins with producers. — Incorrect. This turns the two chains around. Living green plants start the GFC, while dead plant and animal remains start the DFC.
Option (3) In a terrestrial ecosystem, GFC carries a much larger fraction of energy than DFC. — Incorrect. In a terrestrial ecosystem the share is the other way round. A much larger fraction of energy flows through the DFC than through the GFC on land.
Option (4) In an aquatic ecosystem, DFC, rather than GFC, is the major conduit for energy flow. — Incorrect. In an aquatic ecosystem the GFC is the major conduit for energy flow, not the DFC.
NCERT Extract:
Energy Flow – “The detritus food chain (DFC) begins with dead organic matter. It is made up of decomposers which are heterotrophic organisms, mainly fungi and bacteria. They meet their energy and nutrient requirements by degrading dead organic matter or detritus. These are also known as saprotrophs (sapro: to decompose). Decomposers secrete digestive enzymes that breakdown dead and waste materials into simple, inorganic materials, which are subsequently absorbed by them. In an aquatic ecosystem, GFC is the major conduit for energy flow. As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the GFC.”