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2025 · Q40Environment & EcologyBiogeochemical Cycles & Earth Systemsmoderate

With reference to the planet Earth, consider the following statements : I. Rain forests produce more oxygen than that produced by oceans. II. Marine phytoplankton and photosynthetic bacteria produce about 50% of world's oxygen. III. Well-oxygenated surface water contains several folds higher oxygen than that in atmospheric air. Which of the statements given above is/are correct?

  1. (a)I and II
  2. (b)II only
  3. (c)I and III
  4. (d)None of the above statements is correct
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Official answer(b) II only

2011 · Q21Environment & EcologyBiogeochemical Cycles & Earth Systemsmoderate

Human activities in the recent past have caused the increased concentration of carbon dioxide in the atmosphere, but a lot of it does not remain in the lower atmosphere because of 1. Its escape into the outer stratosphere, 2. The photosynthesis by phytoplankton in the oceans, 3. The trapping of air in the polar ice caps. Which of the statements given above is/are correct?

  1. (a)1 and 2
  2. (b)2 only
  3. (c)2 and 3
  4. (d)3 only
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Official answer(b) 2 only