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Organisms and Populations — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYOrganisms and Populations1 Mark
MCQ
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.
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.
  • A
    Both assertion and reason are true and reason is the correct explanation of assertion.
  • B
    Both assertion and reason are true but reason is not the correct explanation of assertion.
  • C
    Assertion is true but reason is false.
  • ✓
    Both assertion and reason are false.
✓

Answer

Correct option: D.
Both assertion and reason are false.
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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