Question

Given figure represents two food chains (X and Y) linked together to form a food web. Identify the types of food chains X and Y and the organism A that interconnects these food chains.

A. X- Detritus food chain, Y- Grazing food chain, A- Bacterium
B. X- Detritus food chain, Y- Grazing food chain, A- Detritivore
C. X- Grazing food chain, Y- Detritus food chain, A- Detritivore
D. X- Grazing food chain, Y- Detritus food chain, A- Grasshopper

Answer 1

Hint: In a grazing food chain, the initial energy is obtained through photosynthesis. This means that the first level consists of living green plants. On the other hand, in a detritus food chain, the initial energy is obtained from dead and decaying matter. The organism A feeds on this dead matter.

Complete answer:
- From the figure, we can see that the initial element in the X chain is a live leaf. This is the producer on which the caterpillar feeds. This is indicative of a grazing food chain.
- The grazing food chain is a type of food chain in which the starting energy of the chain, i.e. the energy in the lowest trophic level is obtained through photosynthesis. Since photosynthesis only occurs in living green plants, we can identify the X chain to be a grazing food chain.
- On the other hand, the detritus food chain is a type of food chain in which the energy of the lowest trophic level is obtained from dead and decaying matter, i.e. detritus.
- So, when we look at the Y chain in the figure, we see that an organism A is feeding on the dead leaf. Detritivores are the organisms which feed on detritus.

Hence, the correct answer is option (C).

Note: In a grazing food chain, producers are the primary source of energy. On the other hand, in a detritus food chain, dead and decaying matter are the primary sources of energy. A compared to the detritus food chain, the grazing food chain is bigger in size. Most of the organisms in a grazing food chain are macroscopic, whereas, the detritus food chain consists of microscopic organisms.