Read following statements and choose the correct option:
A. Pyramid of number in grassland ecosystem is upright.
B. Pyramid of number in tree ecosystem is inverted.
C. Pyramid of biomass in tree ecosystem is inverted.
D. Pyramid of biomass in aquatic ecosystem is inverted.

Question

Read following statements and choose the correct option: 
A. Pyramid of number in grassland ecosystem is upright. 
B. Pyramid of number in tree ecosystem is inverted. 
C. Pyramid of biomass in tree ecosystem is inverted. 
D. Pyramid of biomass in aquatic ecosystem is inverted.

Accepted Answer

The correct option is 1: A and D

Ecological pyramids graphically represent the trophic structure and function of an ecosystem. Statement A is correct because in a grassland ecosystem, the producers (grasses) are vastly numerous, supporting a smaller population of primary consumers (herbivores), which in turn support an even smaller population of secondary consumers. This stepwise decrease in the number of organisms at successive trophic levels creates the typical **upright pyramid of number**. Statement D is also correct because an aquatic ecosystem often exhibits an **inverted pyramid of biomass**. The producers, mainly phytoplankton, have a small standing crop (biomass) at any given moment, but they reproduce and are consumed so quickly that they support a much larger biomass of zooplankton and fish. Since both A and D are correct, this combination is the right choice.

The incorrect option is 2: A, B and C

This option incorrectly includes statement C. Statement C claims that the Pyramid of biomass in a tree ecosystem is inverted. This is factually wrong. A tree ecosystem, whether a single tree or a forest, has a very large single producer (the tree) or many trees at the base, representing a massive amount of biomass. The biomass of the consumers (insects, birds, etc.) it supports is significantly less than the biomass of the producer. Therefore, the pyramid of biomass in a tree ecosystem is always **upright**, not inverted. Since statement C is false, this option is incorrect.

The incorrect option is 3: B, C and D

This option is incorrect because it relies on two false premises as a complete set. As explained for option 2, statement C, "Pyramid of biomass in tree ecosystem is inverted," is false; this pyramid is upright due to the immense biomass of the producer (the tree). Furthermore, while statements B and D are individually correct, the inclusion of the incorrect statement C makes the entire option fundamentally invalid as a description of the correct combination of statements.

The incorrect option is 4: A, B and D

While statements A, B, and D are all individually correct descriptions of their respective ecological pyramids, this option is incorrect because the question asks to choose *the* correct option, and the specified correct option is "A and D." Statement B, "Pyramid of number in tree ecosystem is inverted," is true because one large tree supports numerous small primary consumers. However, in the context of the given MCQ where Option 1 (A and D) is the designated correct answer, selecting a different, larger set of true statements (A, B and D) would be technically incorrect for this specific examination question.