Question

Assertion: As per ecologists, a stable community must be resistant to invasion by alien species.
Reason: It must be resistant to occasional disturbances by nature or human beings.

• A. Both the assertion and reason are true and the reason is the correct explanation of the assertion
• B. Both the assertion and reason are true but the reason is not the correct explanation for the assertion
• C. The assertion is true but the reason is false
• D. Both assertion and the reason are false

Answer 1

The correct option is B Both the assertion and reason are true but the reason is not the correct explanation for the assertion

A stable community is a community which does not show too much variation in productivity from year to year. It should be resistant or resilient to occasional disturbances by caused naturally (such as floods, droughts, etc) or human beings (such as deforestation, colonisation, etc).
It must also be resistant to invasions by alien species. Alien species are non-native organisms that are introduced into a habitat. These species may harm the biotic and abiotic components of the already existing ecosystem.
For example, catfish introduced into a pond will eat all other existing fish and multiply in number. This will drastically reduce the number of prey species and finally result in intraspecific competition between the catfish species which will reduce the productivity of the pond ecosystem.

Hence both the assertion and reason are true but the reason does not correctly explain the assertion.