Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The decomposers of the detritus food chain are also known as saprotrophs.
Reason (R): Some of the organisms of the detritus food chain are prey to the grazing food chain animals.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Both (A) and (R) are true but (R) is not the correct explanation of (A).
The detritus food chain (DFC) begins with dead organic matter. Its decomposers, mainly fungi and bacteria, feed by breaking down this dead matter, and the DFC is also linked with the grazing food chain (GFC) at some points.
Assertion (A): The decomposers of the detritus food chain are also known as saprotrophs. — True. A is about the name and mode of feeding of decomposers. They meet their energy and nutrient needs by degrading dead organic matter, so they are called saprotrophs (sapro: to decompose).
Reason (R): Some of the organisms of the detritus food chain are prey to the grazing food chain animals. — True. R is about the link between the two food chains. Some DFC organisms are eaten by GFC animals, and this joins the chains into a food web.
Why R does not explain A? Decomposers are called saprotrophs because of what they feed on: dead organic matter, which they break down with digestive enzymes and then absorb. R tells us who eats some DFC organisms, which explains how the DFC connects with the GFC. Being eaten by GFC animals has nothing to do with how decomposers get their own food. So both statements are correct, but R is not the explanation of A.
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). … Detritus food chain may be connected with the grazing food chain at some levels: some of the organisms of DFC are prey to the GFC animals, and in a natural ecosystem, some animals like cockroaches, crows, etc., are omnivores.”