UPPSC 2022 Prelims GS Paper-I · Question 148 of 150

Correct — A, Both 1 and 2. Note the printed code before anything else: in this paper (a) is 'Both 1 and 2', (b) is 'Only 1', (c) is 'Neither 1 nor 2' and (d) is 'Only 2' — not the arrangement most candidates have drilled. Statement 1 is a fair paraphrase of the textbook definition: a species' ecological niche covers the range of environmental conditions it can tolerate, the resources it uses, and the functional role it plays in the ecosystem. That three-part formulation is exactly how the concept was built up — Grinnell's habitat niche (1917), Elton's functional or trophic niche (1927), and Hutchinson's n-dimensional hypervolume (1957), which is where the 'range of conditions' language comes from. Statement 2 is the standard corollary drawn from the competitive exclusion principle: two species cannot occupy the same exact niche in a habitat and coexist in a stable way, so each species ends up with a distinct niche. Both statements being correct, the key marks (a).

• (b)Only 1 — It accepts the definition but rejects the distinctness of niches. That would put the item at odds with the competitive exclusion principle, which holds that two species occupying an identical niche cannot coexist stably — the stronger competitor displaces the other, or the two diverge through resource partitioning until their niches differ.
• (c)Neither 1 nor 2 — Both statements are correct, so a blanket rejection fails. Statement 1 is the accepted definition of a niche and statement 2 follows from competitive exclusion; neither is a distortion of the concept.
• (d)Only 2 — It accepts distinctness but rejects the definition, which is the one part of the item that is simply textbook. A niche is precisely the combination of tolerable conditions, resources used and functional role — rejecting statement 1 would leave the question with no working definition at all. The awkward wording of statement 1, which reads as though a clause is missing, is the only reason a candidate would doubt it.

An ecological niche is the match of a species to its environment, described along three axes at once: the range of physical and chemical conditions it can tolerate, the resources it uses, and the functional role it performs in the community — what it eats, what eats it, what it competes with. The standard classroom contrast is that a habitat is a species' address while its niche is its profession: many species can share an address, but the profession is what separates them. Ecologists further split the concept in two. The fundamental niche is the full range of conditions and resources a species could exploit in the absence of competitors and predators; the realised niche is the narrower band it actually occupies once those pressures act on it. Because the realised niches of coexisting species are pushed apart by competition, the distinctness in statement 2 is an outcome of ecological interaction, not an assumption.

The reasoning trap here is that statement 2 sounds like an absolute claim and absolutes are usually wrong in prelims. Two species certainly can share a broad way of life — ecologists call such a group a guild — and can look as though they occupy the same niche. But they differ along some niche dimension: they take different prey sizes, feed at different heights in the canopy, or are active at different times, which is resource partitioning, and over evolutionary time the differences can be sharpened by character displacement. That is why the competitive exclusion principle, first formalised from Gause's experiments, does not deny apparent overlap; it denies stable coexistence in an identical niche. So statement 2 stands as written. The other trap is purely textual: statement 1 is printed without a conjunction and reads clumsily, and a candidate can talk themselves out of a correct statement because it looks garbled. Judge the substance, not the punctuation.

• An ecological niche covers the range of conditions a species tolerates, the resources it utilises, and its functional role in the ecosystem — the three elements named in statement 1.
• The competitive exclusion principle holds that two species cannot occupy the same exact niche in a habitat and coexist in a stable manner; this is the basis of statement 2.
• The fundamental niche is the full range a species could occupy without competition or predation; the realised niche is the narrower range it actually occupies once those pressures act.
• The concept was built in stages — Grinnell (1917) on the habitat niche, Elton (1927) on the functional or trophic niche, and Hutchinson (1957) on the n-dimensional hypervolume.
• Species with broadly similar ways of life coexist by resource partitioning and, over evolutionary time, character displacement — which is how niches stay distinct rather than identical.

• Treating 'habitat' and 'niche' as interchangeable. Habitat is the physical place; the niche adds the resources used and the functional role, which is what statement 1 spells out.
• Rejecting statement 2 because two species obviously live side by side. They coexist by differing along some niche dimension; identical niches are what cannot persist.
• Assuming the usual option code. In this paper 'Only 1' is at (b) and 'Both 1 and 2' at (a), so the meaning must be read off the printed option, not recalled.

Both examinations treat the niche as a definition question. UPSC has asked for the term that covers both physical space and functional role; UPPSC asks it as a two-statement item like this one, or as a 'which statement is NOT true about ecological niche' item, where the trap statement usually inverts the relationship between resource availability and the number of species.

• practice — not a real PYQ

  The range of conditions and resources a species could occupy in the complete absence of competitors and predators is called its

  • (a)realised niche
  • (b)fundamental niche
  • (c)habitat
  • (d)home range

  Answer(b) fundamental niche — the realised niche is the narrower band actually occupied once competition and predation act.

• practice — not a real PYQ

  The competitive exclusion principle states that

  • (a)two species with identical niches cannot coexist stably in the same habitat
  • (b)predators always exclude their prey from a habitat
  • (c)a species occupies a wider niche as competitors increase
  • (d)energy transfer between trophic levels cannot exceed ten per cent

  Answer(a) two species with identical niches cannot coexist stably in the same habitat — the stronger competitor displaces the other unless their niches diverge.