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Unit 3: Biodiversity and the interconnectedness of life
Quick questions on Abiotic and biotic factors, tolerance ranges and ecological niche (QCE Biology Unit 3)
11short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is abiotic factors?Show answer
Abiotic factors are the non-living, physical and chemical conditions of the environment.
What is biotic factors?Show answer
Biotic factors are the influences other organisms have on the species in question.
What is tolerance ranges?Show answer
Every species has a range of values of each abiotic factor within which it can survive and reproduce. Plotted as a tolerance curve (performance against the factor), the curve is bell-shaped with the following zones:
What is ecological niche?Show answer
A species' ecological niche is its multidimensional role in an ecosystem: where it lives, when it is active, what it eats, what eats it, what it requires and what it provides. The niche is summarised along several axes.
What is fundamental niche?Show answer
The full set of conditions under which the species can survive and reproduce, with no competitors or predators present.
What is realised niche?Show answer
The actual subset occupied once species interactions are factored in. Competition usually shrinks the niche; facilitation can expand it.
What is competitive exclusion principle?Show answer
Two species with identical niches cannot coexist indefinitely; the better competitor displaces the other. Coexistence requires niche differentiation (different resources, different times, different microhabitats).
What is confusing habitat and niche?Show answer
Habitat is the where; niche is the role and the conditions across all axes.
What is treating tolerance curves as identical for all factors?Show answer
A species can have a wide tolerance to temperature but a narrow tolerance to salinity. Plot each factor separately.
What is calling everything mutualism?Show answer
Make sure both species genuinely benefit; one-sided benefit is commensalism, harm is parasitism.
What is ignoring interactions?Show answer
Distribution rarely reflects abiotic factors alone. Competition, predation, disease and disturbance routinely shrink the realised niche.