Question

Which of the following ecological pyramid is always inverted?

• A. Pyramid of Number in Grassland ecosystem
• B. Pyramid of Number in Parasitic food chain
• C. Pyramid of Biomass in forest ecosystem
• D. Pyramid of energy in grassland ecosystem

Hint:

Pyramid Inversion Rules:
- Pyramid of Energy: Never inverted (always upright).
- Pyramid of Numbers: Inverted in parasitic food chains; spindle-shaped in a tree ecosystem.
- Pyramid of Biomass: Inverted in aquatic ecosystems (phytoplankton vs. fish).

Answer 1

The Correct Option is B

Concept:
Ecological pyramids, introduced by Charles Elton, graphically depict the trophic structure of an ecosystem across successive feeding levels.
They illustrate the distribution of numbers, dry biomass, or energy flow from primary producers ($T_1$) to apex predators ($T_n$).
An upright pyramid has a wide base tapering toward the top, whereas an inverted pyramid has a narrow base that broadens at higher trophic levels.

Step 1: Evaluation of Each Ecological Pyramid Option:
1. Pyramid of Number in Grassland ecosystem: Upright. Millions of individual grass plants form a broad base supporting thousands of herbivorous insects, which in turn support smaller numbers of insectivorous birds and apex raptors.
2. Pyramid of Biomass in forest ecosystem: Upright. The standing crop biomass of massive perennial trees (wood, roots, foliage) is far greater than the biomass of herbivorous animals, which exceeds that of top carnivores.
3. Pyramid of Energy in grassland ecosystem: Always upright. Under the Second Law of Thermodynamics and Lindeman's 10% law, energy is dissipated as metabolic heat at each transfer, so energy content declines at every successive trophic level across all ecosystems without exception.
4. Pyramid of Number in Parasitic food chain: Always inverted. A single primary producer (e.g., an oak tree) acts as host to hundreds of herbivorous birds or mammals. Each bird hosts thousands of ectoparasites and endoparasites (lice, ticks, and helminths), and each parasite can harbor millions of hyperparasitic bacteria and protozoa. The count of individuals increases at each successive trophic step.

Step 2: Conclusion on Shape Inversion:
Because individual organism counts continuously multiply as one moves up a parasitic food chain, its pyramid of numbers is consistently inverted.
Final Answer:
The pyramid of numbers in a parasitic food chain is always inverted, corresponding to option (B).