Class 12 · Ecosystem

Primary Productivity Variation Across Ecosystems — NEET

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📖 NCERT Source

Primary productivity depends on the plant species inhabiting a particular area. It also depends on a variety of environmental factors, availability of nutrients and photosynthetic capacity of plants. Therefore, it varies in different types of ecosystems. The annual net primary productivity of the whole biosphere is approximately 170 billion tons (dry weight) of organic matter. Of this, despite occupying about 70 per cent of the surface, the productivity of the oceans are only 55 billion tons. Rest of course, is on land. Discuss the main reason for the low productivity of ocean with your teacher.

NCERT Biology · Class 12 · Chapter 12 · Paragraph 11
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Assertion (A): Primary productivity varies significantly among different ecosystems. Reason (R): Primary productivity depends on plant species, environmental factors, nutrient availability, and photosynthetic capacity of plants.

📖 Solution & NCERT Explanation
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Correct answer: A If both assertion and reason are true and the reason is the correct explanation of the assertion.

NCERT confirms productivity varies among ecosystems and states “Primary productivity depends on the plant species inhabiting a particular area. It also depends on a variety of environmental factors, availability of nutrients and photosynthetic capacity of plants.” Both statements are true from NCERT. The Reason correctly explains WHY productivity varies - multiple interacting factors create different productivity levels in different ecosystems.

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What does NCERT say about Primary productivity depends on?
Primary productivity depends on the plant species inhabiting a particular area. It also depends on a variety of environmental factors, availability of nutrients and photosynthetic capacity of plants.
Has this concept appeared in NEET?
Practice this NCERT concept with questions on MedicNEET.
Which chapter is this from?
Ecosystem, Class 12 NCERT Biology.

Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.

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