Q. 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?
(a) I and II
(b) II only
(c) I and III
(d) None of the statements is correct
Correct Answer : (b) II only
UPSC Prelims 2025 GS Paper's Solution
Explanation :
Statement 1 & 2: Scientists estimate that roughly half of the oxygen production on Earth comes from the ocean. The majority of this production is from oceanic plankton — drifting plants, algae, and some bacteria that can photosynthesize. One particular species, Prochlorococcus, is the smallest photosynthetic organism on Earth.
Source : https://oceanservice.noaa.gov/facts/ocean-oxygen.html
Statement 3 : Well-oxygenated surface water may only contain around 8 mg O2/l, while the air contains 210 mg O2/l.
