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Organisms and Populations — NEET MCQs with answers
Chapter 11 introduces ecology at the population level, exploring how organisms interact with each other and with their abiotic environment. It examines population attributes such as birth rate, death rate, age distribution and sex ratio, the exponential and logistic models of population growth, and the major types of interspecific interactions - predation, competition, parasitism, commensalism, mutualism and amensalism.
Topics in this chapter
- 11.1 Populations
Free practice questions
The term 'asymptote' in the logistic growth curve refers to:
- A. the plateau reached when N equals the carrying capacity
- B. the point where the population becomes zero
- C. the steepest rising part of the curve
- D. the initial slow-growth phase
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Answer: A — The asymptote is the final flat portion of the sigmoid curve, reached when the population density equals the carrying capacity K and growth halts.
NCERT Class 12 Biology · Ch 11 · 11.1 Populations
In logistic growth, the phase in which the population density is close to K and the growth rate slows down markedly is the:
- A. deceleration phase
- B. lag phase
- C. exponential phase
- D. acceleration phase
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Answer: A — After acceleration, a deceleration phase occurs (growth slows) before the asymptote is reached at the carrying capacity.
NCERT Class 12 Biology · Ch 11 · 11.1 Populations
The example given in NCERT for a population size as low as less than 10 in any year is:
- A. Lotus plants in a pond
- B. Siberian cranes at Bharatpur wetlands
- C. Bacteria in a petri dish
- D. Chlamydomonas in a pond
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Answer: B — NCERT states the population size could be as low as <10 (Siberian cranes at Bharatpur wetlands in any year).
NCERT Class 12 Biology · Ch 11 · 11.1 Populations
In the logistic growth equation dN/dt = rN(K−N)/K, the symbol 'N' stands for:
- A. the number of years
- B. the intrinsic rate of natural increase
- C. population density at time t
- D. the carrying capacity
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Answer: C — In the logistic equation, N is the population density at time t, r is the intrinsic rate of natural increase and K is the carrying capacity.
NCERT Class 12 Biology · Ch 11 · 11.1 Populations
Which of the following is NOT a population attribute mentioned in NCERT?
- A. Population density
- B. Sex ratio
- C. Age distribution
- D. Body temperature
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Answer: D — NCERT lists birth rate, death rate, sex ratio, age distribution and density as population attributes. 'Body temperature' is an individual physiological trait, not a population attribute.
NCERT Class 12 Biology · Ch 11 · 11.1 Populations
In the king-and-minister chess anecdote in NCERT, 1 grain is placed on Square 1, 2 on Square 2, 4 on Square 3, 8 on Square 4, doubling each time. How many grains in total lie on the first 6 squares?
- A. 32
- B. 63
- C. 64
- D. 127
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Answer: B — The squares carry 1, 2, 4, 8, 16 and 32 grains; their sum is 63 (= 2^6 − 1). 32 is the grains on Square 6 alone; 64 is 2^6, one more than the true total; 127 is the total on the first 7 squares (NCERT p.195, exponential growth anecdote).
NCERT Class 12 Biology · Ch 11 · 11.1 Populations
According to NCERT, which group appears to be more adversely affected by competition?
- A. Parasites, more than hosts
- B. Carnivores, more than herbivores
- C. Herbivores and plants, more than carnivores
- D. Decomposers, more than producers
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Answer: C — The text states that, in general, herbivores and plants appear to be more adversely affected by competition than carnivores.
NCERT Class 12 Biology · Ch 11 · 11.1 Populations
Brood parasitism is classified under which broad category of population interaction?
- A. mutualism
- B. parasitism
- C. commensalism
- D. amensalism
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Answer: B — NCERT explicitly calls brood parasitism a fascinating example of parasitism.
NCERT Class 12 Biology · Ch 11 · 11.1 Populations
Which statement about the exponential growth curve is correct?
- A. It is J-shaped and does not level off
- B. It includes carrying capacity in its equation
- C. It is S-shaped and levels off at K
- D. It requires limited resources
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Answer: A — The exponential curve is J-shaped, arises under unlimited resources, and has no upper limit set by carrying capacity — so it does not level off.
NCERT Class 12 Biology · Ch 11 · 11.1 Populations
In the Ophrys–bee interaction, pollen is transferred when the male bee:
- A. pseudocopulates with the flower and gets dusted with pollen
- B. lays eggs in the flower
- C. eats the nectar
- D. builds a nest in the flower
Show answer
Answer: A — NCERT: the male bee, attracted to what it perceives as a female, 'pseudocopulates' with the flower and is dusted with pollen, which it transfers to another flower.
NCERT Class 12 Biology · Ch 11 · 11.1 Populations
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