Which of the following statements is not true about "ecological niche" ?

Question

UnlockIAS · Accepted Answer

Correct — C, 'Number of species becomes small in ecological niche, if resources are sufficient.' This is the statement that is not true, and the question asks for exactly that. Abundant resources do the opposite of shrinking species numbers: when food, light, water, nesting space and nutrients are plentiful, competition for any single resource is relaxed, no species is forced out, and the resource axes can be finely subdivided among many co-existing species — resource partitioning. That is why species-rich systems such as tropical rainforests, coral reefs and the Terai grasslands of Uttar Pradesh are exactly the systems with high productivity and a long, uninterrupted supply of resources, while resource-poor systems (deserts, high alpine zones, polar regions) carry few species. Statement (c) also contradicts statement (b) word for word, so one of the two must be false; since (b) is the ecologically standard claim, (c) is the untrue one.

Why the other options are wrong — (a) True, so it cannot be the answer. In community ecology a dominant species is one that contributes most of the biomass or abundance and exerts the strongest control on community structure. Such species are typically broad-niched generalists — tolerant of a wide range of conditions and able to use many resources — which is precisely what lets them spread across a large part of the habitat. Narrow-niched specialists, by contrast, are usually restricted and rarely dominant.  (b) True, so it is not the answer — and it is the direct contradiction of option (c). Where resources are sufficient, competitive pressure eases, niches can be partitioned along more dimensions (feeding height, prey size, time of activity, microhabitat), and more species coexist. This is the standard explanation for the higher species richness of productive, stable, resource-rich ecosystems.  (d) True, so it is not the answer. If resources are spread evenly across a habitat rather than concentrated in patches, no single species can monopolise a resource-rich core and convert that advantage into dominance. The community then shows high evenness and low dominance — which is exactly what dominance and evenness indices (Simpson's index, Shannon's index) measure.

Concept: An ecological niche is not a place — it is the complete set of conditions and resources under which a species can maintain a viable population, together with the functional role it plays in the community. The classic contrast is that a habitat is a species' 'address' while its niche is its 'profession'. Joseph Grinnell (1917) framed the niche spatially, Charles Elton (1927) framed it functionally as the organism's role in food webs, and G. Evelyn Hutchinson (1957) unified both as an n-dimensional hypervolume, distinguishing the fundamental niche (where a species could live in the absence of competitors) from the realised niche (the smaller space it actually occupies once competitors are present).

State PCS 2024 Q9 — Environment & Ecology PYQ with Answer

State PCS 2024 Q9 — Environment & Ecology PYQ with Answer