Question

Which of the following food chains shows a spindle shaped pyramid of numbers?
A. Grass- insect- frog
B. Phytoplankton- zooplankton- small fish
C. Trees- birds- hawks
D. Tree- birds- insects- bacteria

Answer 1

Hint: Spindle shaped pyramid is Having the shape of a spindle, which is wide in the centre and tapered at both ends. Because the base \[\left( {T1} \right)\] is occupied by large sized trees (Producer) that are few in number, the number pyramid in a forest ecosystem is spindle in shape. Herbivores \[\left( {T2} \right)\] (fruit-eating birds, elephants, and deer) are more numerous than producers in the second trophic level. The eagle population is, however, quite modest.

Complete answer:
Option A: Because energy transmission in a food chain is always unidirectional, the energy pyramid is the only type of ecological pyramid that is always upright. In addition, as the trophic level rises, some energy is lost to the environment.
So, this option A is incorrect.
Option B: Except in oceans, where enormous numbers of zooplanktons rely on a relatively small number of phytoplanktons, the biomass pyramid is also upright.
Hence this is an incorrect option.
Option C: A single major producer, like a tree, provides food to multiple herbivores, such as birds, in a forest environment, and these little herbivorous birds are typically eaten by falcons or eagles. The eagle population is, however, quite modest. As a result, the number pyramid derived from this type of interaction is spindle-shaped.
 So, option C is Correct.
Option D: In a forest setting, a single major producer, such as a tree, gives food to several herbivores, such as birds, and these small herbivorous birds are often consumed by falcons or eagles. The eagle population, on the other hand, is fairly small. As a result, this form of interaction produces a spindle-shaped number pyramid.
So, option D is not correct.

Therefore, Option C is the correct answer.

Note:
Ecological pyramids depict the proportionate amount of energy or matter in each trophic level of a food chain or food web. Pyramids of energy, biomass, and numbers are the three types. A forest ecosystem’s number pyramid is fashioned like a spindle. The number of producers in a forest ecosystem is lower, but it supports a higher number of herbivores. As a result, there are fewer carnivores in the area. As a result, the pyramid of numbers has a spindle-shaped structure.