Read the following statements about energy flow through the grazing food chain (GFC) and the detritus food chain (DFC):
I. In an aquatic ecosystem, the grazing food chain (GFC) is the major conduit for energy flow.
II. The decomposers of the DFC are mainly autotrophic organisms.
III. In a terrestrial ecosystem, a much larger fraction of energy flows through the DFC than through the GFC.
Which of the statements given above are correct?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → I and III
I. In an aquatic ecosystem, the grazing food chain (GFC) is the major conduit for energy flow. — True. In water most of the energy passes along the GFC, which begins with the producers.
II. The decomposers of the DFC are mainly autotrophic organisms. — False. The DFC begins with dead organic matter. Its decomposers, mainly fungi and bacteria, are heterotrophic; they get energy by breaking down detritus. Autotrophs make their own food and are the producers of the GFC.
III. In a terrestrial ecosystem, a much larger fraction of energy flows through the DFC than through the GFC. — True. On land a large part of plant matter dies without being eaten, so more energy passes through 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. … 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.”