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Biodiversity and Conservation — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYBiodiversity and Conservation1 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: Alpha diversity is said to be higher if the dissimilarity between communities is higher.
Reason: Alpha diversity is a measure of diversity between the communities.
✓

Answer

  1. Both assertion and reason are false.

Explanation:

Diversity at the level of community and ecosystem has three perspectives which are called Alpha, Beta and Gamma diversity. Alpha diversity (within - community diversity) refers to the diversity of organisms sharing the same community/ habitat. A combination of species richness and equitability/ evenness is used to represent diversity within a community or habitat. Species richness is the number of species per unit area. The number of species increases with the area of the site. Generally, greater the species richness, greater is the species diversity. However, number of individuals among the species may also vary, resulting into differences in evenness or equitability and consequently in diversity.

Species frequently change when habitat or community changes. The rate of replacement of species along a gradient of habitats or communities is called beta diversity (between - community diversity). There are differences in species composition of communities along environmental gradients, e.g., altitudinal gradient, moisture gradient, etc. Higher the heterogeneity in the habitats in a region or greater the dissimilarlty between communities, higher is the beta diversity. Diversity of the habitats over the total landscape or geographical area is called gamma diversity.

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