Question

Which one of the following statements is wrong regarding ecological pyramids?

• A. They do not include saprophytes (decomposers)
• B. Insect feeding on a big tree is an example of inverted pyramid of numbers
• C. The pyramid of biomass in a sea is inverted
• D. They consider the same species belonging to two or more trophic levels

Answer 1

The Correct Option is D

To evaluate which statement is incorrect about ecological pyramids, we should review what ecological pyramids represent and their fundamental characteristics.

1. Exclusion of Saprophytes: Ecological pyramids typically depict the flow of energy, numbers, or biomass through different trophic levels in an ecosystem. Saprophytes, or decomposers, are usually not shown because they function at all levels by breaking down dead organic matter. 

2. Inverted Pyramid of Numbers: In some ecosystems like forests, a single large tree may support many herbivores such as insects. This situation creates an inverted pyramid of numbers where the base (plants) is smaller than the primary consumer level.

3. Inverted Pyramid of Biomass: In ocean ecosystems, the biomass of phytoplankton is less than that of the zooplankton that feed on them due to rapid reproduction rates and turn over of phytoplankton, resulting in an inverted pyramid of biomass.

4. Species Overlapping Trophic Levels: Ecological pyramids typically assume that each organism only occupies one trophic level. However, some species can operate at multiple levels, such as omnivores that eat both plants and animals, but this is not depicted in these pyramids.

Given these clarifications, the wrong statement about ecological pyramids is: They consider the same species belonging to two or more trophic levels. Ecological pyramids generally do not account for species interacting across multiple trophic levels, which is why this statement is inaccurate.

Answer 2

Let's evaluate each statement regarding ecological pyramids:

(1) They do not include saprophytes (decomposers): This is correct. Ecological pyramids typically represent trophic levels based on producers, primary consumers, secondary consumers, etc., but decomposers (saprophytes) are generally not included in the pyramid. They play an important role in breaking down dead organic material, but are not typically counted in these pyramids.

(2) Insect feeding on a big tree is an example of an inverted pyramid of numbers: This is correct. In some ecosystems, especially in cases where a few large organisms (like trees) support many smaller organisms (like insects), the pyramid of numbers can be inverted. The number of insects would exceed the number of trees, making the pyramid appear upside down.

(3) The pyramid of biomass in a sea is inverted: This is correct. In marine ecosystems, especially in the case of phytoplankton and zooplankton, the biomass pyramid can be inverted. Phytoplankton have a very short lifespan and small biomass, but they are consumed rapidly by larger zooplankton, leading to more biomass in consumers than producers.

(4) They consider the same species belonging to two or more trophic levels: This is incorrect. Ecological pyramids generally do not consider the same species at multiple trophic levels. Each trophic level represents different species or groups of organisms that fulfill different roles in the food chain. A single species should belong to only one trophic level in a pyramid.

Thus, the wrong statement is (4) They consider the same species belonging to two or more trophic levels.

The correct answer is (4).