Question

Assertion :Oceans are a low productivity ecosystems despite occupying about $70\%$ of the earth's surface. Reason: In aquatic ecosystems, productivity is limited by light which decreases with increasing water depth.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Productivity levels of an ecosystem depend upon plant species inhabiting a particular area, their photosynthetic capacity, availability of nutrients, sunlight, moisture and a variety of other environmental factors. The annual net primary productivity of the whole biosphere is approx. 170 billion tons(dry weight) of organic matter. Of this, despite occupying about 70% of earth's surface, oceans contribute only 32% of total productivity(55 billion tons out of 170 billion tons). thus, oceans are low productivity ecosystems. It is because, in oceans, productivity is limited by light which decreases with increasing water depth.

So, the correct answer is 'Both Assertion and Reason are correct and Reason is the correct explanation for Assertion'.