Biology · Ecosystems · NEET
The starting point is different. A grazing food chain (GFC) begins with living producers, that is, green plants. A detritus food chain (DFC) begins with dead organic matter called detritus. So GFC starts from something alive, and DFC starts from something dead. This one point (living vs dead start) is the answer NEET wants most often.
NCERT is very clear on this. In an aquatic (water) ecosystem, the grazing food chain (GFC) is the major path for energy flow. In a terrestrial (land) ecosystem, a much larger fraction of energy flows through the detritus food chain (DFC) than through the GFC. Students often flip these two, so remember: water = GFC leads, land = DFC leads.
The DFC is made up of decomposers, which are heterotrophic organisms, mainly fungi and bacteria. They are also called saprotrophs (sapro means to decompose). They secrete digestive enzymes that break down dead and waste materials into simple inorganic substances, which they then absorb.
No, they are connected. NCERT says the DFC may be connected with the GFC at some levels. Some organisms of the DFC are prey (food) for GFC animals. Also, some animals like cockroaches and crows are omnivores. These natural interconnections of food chains form a food web.
Because energy transfer follows the 10 percent law. Only about 10 percent of energy passes to each next trophic level from the level below it. So energy runs out after a few levels (producer, herbivore, primary carnivore, secondary carnivore), which limits how long a GFC can be.
Not directly at its start. The GFC depends directly on the sun because producers capture solar energy first. The DFC starts from dead matter (detritus), so it uses energy already stored in that dead matter. But remember, that dead matter originally came from producers, so the sun is still the ultimate source.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
GFC stands for Grazing Food Chain and DFC stands for Detritus Food Chain. These are the two exact short forms used in NCERT Class 12 Biology, chapter Ecosystem.
The detritus food chain begins with dead organic matter (detritus). NCERT states: the death of an organism is the beginning of the detritus food chain/web.
No. Decomposers (mainly fungi and bacteria) belong to the detritus food chain. The grazing food chain contains producers, herbivores and carnivores, not decomposers.
Yes. Omnivores like cockroaches and crows link the two chains, and organisms of the DFC can be eaten by GFC animals. These links join the chains into a food web.
When any organism dies it becomes detritus (dead biomass), which serves as the energy source for decomposers in the DFC. So energy not eaten in the GFC flows into the DFC after death.
