Ecosystem MCQs for NEET — Botany Questions with Answers

The pyramid of energy is always upright because according to the 10% law, only 10% of the energy is transferred from one trophic level to the next. This means there is always less energy at higher trophic levels than at lower ones, making an inverted energy pyramid impossible. Pyramids of number and biomass can be inverted in certain ecosystems.

As stated in the text, 'The base of each pyramid represents the producers or the first trophic level while the apex represents tertiary or top-level consumer.'

The exercise question asks: 'In an ecosystem dominated by trees, the pyramid (of numbers) is_________type.' This implies an inverted pyramid of numbers. A single large tree can support many herbivores (e.g., insects), which in turn support fewer carnivores, leading to an inverted shape.

The text clearly states, 'However, there are certain limitations of ecological pyramids such as it does not take into account the same species belonging to two or more trophic levels. It assumes a simple food chain, something that almost never exists in nature; it does not accommodate a food web.'

Figure 12.4 (c) notes 'Inverted pyramid of biomass - small standing crop of phytoplankton supports large standing crop of zooplankton'. This indicates that phytoplankton, though having a smaller standing crop (biomass) at any given time, forms the base, supporting a larger biomass of zooplankton.

The text states, 'This, relationship is expressed in terms of number, biomass or energy.'

The text mentions, 'The important point to note is that the amount of energy decreases at successive trophic levels.'

The limitations section states, 'Moreover, saprophytes are not given any place in ecological pyramids even though they play a vital role in the ecosystem.' This is due to the simplification of food chains.

Figure 12.4 (a) states, 'Pyramid of numbers in a grassland ecosystem. Only three top-carnivores are supported in an ecosystem based on production of nearly 6 millions plants.' This illustrates the sharp decrease in numbers at higher trophic levels.

The text defines standing crop as, 'Each trophic level has a certain mass of living material at a particular time called as the standing crop.'