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Question Bank [2022] — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYQuestion Bank [2022]4 Marks
Question
Long answer question.

By taking industrial melanism as one example. Explain the concept of natural selection.

✓

Answer

  1. Natural selection encourages those genes or traits that assure the highest degree of adaptive efficiency between the population and its environment.
  2. Industrial melanism is one of the best examples of natural selection.
  3. In Great Britain, before industrialization (1845) grey white-winged moths (Biston betularia) were more in number than black-winged moth (Biston carbonara).
  4. These moths are nocturnal and during the day time they rest on a tree trunk.
  5. White-winged moths were camouflaged (hide in the background) well with the lichen-covered trees that helped them to escape from the predatory birds.
  6. However, the black-winged moth resting on lichen-covered tree trunks were easy victims for the predatory birds and their number was reduced.
  7. During the industrial revolution, large number of industries came up in Great Britain.
  8. The industries released black sooty smoke that covered and killed the lichens growing on a tree and turn the tree black due to pollution.
  9. This change became an advantage to the black-winged moths that camouflaged well with the black tree trunks and their number increased
  10. The white-winged moths however became victims to predatory birds due to which their number reduced. Thus, natural selection has resulted in the establishment of a phenotypic trait in the changing environmental conditions.

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