Choose the correct statements from the following:
A. The detritus food chain is made up of decomposers, which are heterotrophic organisms, mainly fungi and bacteria.
B. Decomposers secrete digestive enzymes that break down dead and waste materials into simple, organic materials, which are subsequently absorbed by them.
C. In a natural ecosystem, some animals like cockroaches and crows are omnivores, and such natural interconnection of food chains makes it a food web.
D. Decomposers meet their energy and nutrient requirements by degrading dead organic matter or detritus.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A, C and D only
The detritus food chain (DFC) starts from dead organic matter, not from living plants. Its members are the decomposers, also called saprotrophs. They release digestive enzymes outside their bodies, and the broken-down matter ends up as simple, inorganic materials, which they then absorb.
A. The detritus food chain is made up of decomposers, which are heterotrophic organisms, mainly fungi and bacteria. — True. Decomposers cannot make their own food, so they are heterotrophs. Fungi and bacteria are the main ones.
B. Decomposers secrete digestive enzymes that break down dead and waste materials into simple, organic materials, which are subsequently absorbed by them. — False. The end products are simple inorganic materials, not organic ones. Breaking organic matter down to inorganic substances is the whole point of decomposition.
C. In a natural ecosystem, some animals like cockroaches and crows are omnivores, and such natural interconnection of food chains makes it a food web. — True. An omnivore feeds at more than one point, so it links the grazing and detritus food chains. These cross-links turn separate chains into a web.
D. Decomposers meet their energy and nutrient requirements by degrading dead organic matter or detritus. — True. Detritus is both their food and their energy source.
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.”
Energy Flow – “… 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. These natural interconnection of food chains make it a food web.”