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NEET Biology · Ecology and Environment

Population attributes and interactions

Taught in NCERT Class 12 Biology, Chapter 11: Organisms and Populations.

4 verified questions: Easy 0 · Medium 3 · NEET level 1

Sample questions

Sample 1Medium

A graph of population density against time shows an S-shaped (sigmoid) curve levelling off at the carrying capacity K. For this population, r = 0.5 per year, K = 1000 individuals and the present size N = 200 individuals. Using the logistic equation dN/dt = rN[(K − N)/K], what is the present growth rate?

  1. A

    80 individuals per year

  2. B

    100 individuals per year

  3. C

    160 individuals per year

  4. D

    20 individuals per year

Show the answer
The answer is A.

dN/dt = 0.5 × 200 × (1000 − 200)/1000 = 100 × 0.8 = 80 individuals per year. Logistic growth slows as N approaches K, giving the sigmoid curve.

  • B.

    This is rN, the exponential rate that ignores the limit set by K.

  • C.

    This doubles the correct value; the correct calculation gives 0.5 × 200 × 0.8 = 80.

  • D.

    This uses N/K (0.2) in place of (K − N)/K (0.8).

NCERT: Class 12 Biology, Chapter 11, 11.1

Sample 2NEET level

Match List I (interaction between two species) with List II (effect on the two species). List I: A. Mutualism B. Commensalism C. Amensalism D. Competition List II: I. (−, −) II. (+, 0) III. (−, 0) IV. (+, +) Choose the correct answer.

  1. A

    A-IV, B-III, C-II, D-I

  2. B

    A-II, B-IV, C-III, D-I

  3. C

    A-IV, B-II, C-I, D-III

  4. D

    A-IV, B-II, C-III, D-I

Show the answer
The answer is D.

In mutualism both species benefit (+, +), and in commensalism one benefits while the other is unaffected (+, 0). In amensalism one is harmed and the other unaffected (−, 0), and in competition both lose (−, −).

  • A.

    Swaps commensalism and amensalism.

  • B.

    Swaps mutualism and commensalism.

  • C.

    Swaps amensalism and competition.

NCERT: Class 12 Biology, Chapter 11 (Organisms and Populations), Population interactions

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