Assertion (A): Overexploitation of resources causes biodiversity loss. This statement is accurate. Practices like overfishing, deforestation, and excessive hunting deplete natural resources, leading to a reduction in biodiversity. When species are exploited at a rate exceeding their reproductive capacity, population numbers decrease, resulting in a decline in biodiversity. Consequently, the assertion is valid.
Reason (R): The introduction of Clarias gariepinus into Indian rivers has reduced native Indian fish populations. This statement is also accurate. Clarias gariepinus, or the African catfish, was introduced to Indian rivers for aquaculture. It subsequently became an invasive species, competing with native fish for food and habitat, which led to a decline in native fish populations. While this is true, it does not directly explain how overexploitation of resources leads to biodiversity loss. The introduction of an invasive species is a separate factor contributing to biodiversity loss, not a direct result of overexploitation.
Conclusion: Both the assertion and the reason are true, but the reason does not directly explain the assertion. The correct answer is (B).