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Organisms and Populations — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYOrganisms and Populations1 Mark
Question
For question two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
Assertion: Biotic potential is realised only when the environmental conditions are limiting.
Reason: Under such conditions only, the population size can increase at the maximum rate.
✓

Answer

  1. Both assertion and reason are false.

Explanation:

The inherent maximum capacity of an organism to reproduce or increase in number is termed as biotic potential (designated by the symbol 'r). Biotic potential is realised only when the environmental conditions are non-limiting, so that natality rate (birth - rate) is maximum and mortality rate (death - rate) is minimum. Under these conditions, population size increases at the maximum rate. However, nature keeps a check on the expression of biotic potential. For example, if a pair of flies is allowed to reproduce unchecked, the fly population may outweigh the earth in a few years. The environmental check on population size, or its biotic potential is called environmental resistance. With increase in population size, the environmental resistance (against the population) tends to increase. The environmental resistance represents the limiting effect of abiotic (e.g., water, space) and biotic factors (e.g., food, competition) that do not allow organisms to attain their biotic potential and keep the population size at a much lower level.

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