NEET-Pattern Practice Questions

Section 14 — NEET-Pattern Practice Questions (Organisms and Populations)

Organisms and Populations is a high-yield, dependable NEET chapter — it is consistently well represented, with multiple questions in most years — and most of them are gettable if your core facts are tight. The questions sweep across the whole chapter: population attributes (birth and death rates, sex ratio, age pyramids), how density is measured, the four basic processes of growth, exponential versus logistic growth and the meaning of the intrinsic rate of natural increase $r$, life history strategies, and the six interspecific interactions with their classic examples.

This section is a focused 28-question NEET-pattern practice quiz covering the entire chapter — a mix of straight recall (which curve, which interaction, which example), a few small numericals on birth rate, death rate and $r$, and concept traps that separate exponential from logistic growth and one interaction sign from another.

Important note: These are NEET-pattern practice questions built on the recurring core concepts of this chapter. Do not treat them as exact authenticated year-tagged papers unless each one is separately matched against an official NEET paper and year.

How to use: Treat this like a timed mock — give yourself about 30 minutes for all 28 questions (roughly a minute each). Attempt first, then read each explanation. Skim the Mini Quick Recap below to spot the recurring question patterns before you begin.

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Mini Quick Recap — NEET's Top Hooks for This Chapter

Most questions on Organisms and Populations fall into these recurring patterns.

1. Population attributes. An individual has births and deaths; a population has birth rates, death rates, sex ratio and age distribution. Birth rate = new individuals added divided by the initial number; death rate = deaths divided by the initial number. The age pyramid shape shows whether a population is growing, stable or declining. Density is designated $N$; when counting is meaningless (one huge banyan versus many carrot-grass plants), use per cent cover or biomass.

2. The four basic processes. Density rises through natality and immigration, falls through mortality and emigration: $$N_{t+1} = N_t + [(B + I) - (D + E)]$$

3. Growth equations (memorise all three). Exponential (unlimited resources, J-shaped curve): $$\frac{dN}{dt} = rN$$ $$N_t = N_0 e^{rt}$$ Logistic (limited resources, sigmoid curve, carrying capacity $K$, Verhulst-Pearl): $$\frac{dN}{dt} = rN\left(\frac{K - N}{K}\right)$$ Here $r$ is the intrinsic rate of natural increase, $e = 2.71828$, and when $N = K$ the growth rate becomes zero. Sample $r$ values: Norway rat $0.015$, flour beetle $0.12$.

4. Interaction signs and classic examples. Assign $+$ (benefit), $-$ (harm), $0$ (no effect):

• Mutualism ($+\,+$): lichens (fungus with alga or cyanobacterium), mycorrhizae, fig and wasp, Ophrys orchid and bee.
• Competition ($-\,-$): Balanus excluding Chthamalus (Connell); Abingdon tortoise and goats; MacArthur's warblers show resource partitioning instead of exclusion.
• Predation ($+\,-$): starfish Pisaster keeps intertidal diversity; prickly pear cactus controlled by a moth; plant defences such as thorns and Calotropis cardiac glycosides.
• Parasitism ($+\,-$): Cuscuta on hedge plants; brood parasitism by the cuckoo (koel); liver fluke with two intermediate hosts.
• Commensalism ($+\,0$): orchid on a mango branch, barnacles on a whale, cattle egret and grazing cattle, clown fish and sea anemone.
• Amensalism ($-\,0$): one species harmed, the other unaffected (standard non-NCERT illustration: a mould releasing a substance that kills nearby bacteria).

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