In case of which one of the following biogeochemical cycles, the weathering of rocks is the main source of release of nutrient to enter the cycle?
- A.Carbon cycle
- B.Nitrogen cycle
- C.Phosphorus cycle
- D.Sulphur cycle
Correct answer
Explanation
The correct answer is C, Phosphorus cycle. Phosphorus has no gaseous form in the cycle, so it enters ecosystems mainly when phosphate rocks weather.
The phosphorus cycle is a sedimentary cycle. Its main reservoir is the Earth's crust, in phosphate rocks. Rain and weathering slowly release phosphate ions into soil and water, where plants take them up; animals get phosphorus by eating plants, and decomposers return it to the soil. Much of it finally settles in ocean sediments and returns to land only when those layers are uplifted over geological time. Phosphorus is needed for DNA, ATP, bones and teeth.
A is wrong: the carbon cycle is a gaseous cycle; carbon enters mainly as carbon dioxide from the air.
B is wrong: nitrogen comes from the atmosphere, which is 78% nitrogen, through fixation by bacteria and lightning.
D is wrong: sulphur comes from both rocks and the air (volcanoes, fuel burning), so rock weathering is not its main source.
Exam tip: gaseous cycles = carbon, nitrogen, oxygen; sedimentary cycle = phosphorus (reservoir: rocks).
Practice Questions
View allOne carbon credit is accepted as equivalent to
- A.100 kg of carbon
- B.100 kg of carbon dioxide
- C.1000 kg of carbon
- D.1000 kg of carbon dioxide
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One carbon credit stands for one tonne of carbon dioxide, or its equivalent in other greenhouse gases, kept out of the atmosphere.
Read the full explanation →Which one among the following reports defines Sustainable Development as development that meets the needs of the present generation without compromising the ability of future generations to meet their own needs?
- A.Brundtland Report
- B.United Nations Human Development Report
- C.Agenda-21 of the Rio Earth Summit
- D.OECD Policy Brief (2006)
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This 1987 report gave the world the standard definition of sustainable development quoted in the question. The report, titled Our Common Future, was prepared by the World Commission on Environment and Development, set up by the United Nations in 1983.
Read the full explanation →The 'Ramsar Convention' relates to which one of the following areas ?
- A.Wetland preservation
- B.Promote afforestation
- C.Action plan on climate change
- D.Combat desertification
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The Ramsar Convention is the international treaty for the conservation and wise use of wetlands. It was signed on 2 February 1971 at Ramsar, a town in Iran on the Caspian Sea, and came into force in 1975.
Read the full explanation →A new species of pit-viper was discovered in 2019 and named after the State in which it was found. Identify the State from among the following :
- A.Kerala
- B.Arunachal Pradesh
- C.Andaman and Nicobar Islands
- D.Assam
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The species was named Trimeresurus arunachalensis, the Arunachal pit viper, after the state where it was found. Pit vipers are venomous snakes with a heat-sensing pit between each eye and nostril, which lets them detect warm-blooded prey in the dark.
Read the full explanation →Cheetahs were recently re-introduced to India from Africa. From which language is the name 'Cheetah' derived ?
- A.Swahili
- B.Afrikaans
- C.Somali
- D.Sanskrit
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The word comes from the Sanskrit 'chitraka', meaning the spotted or speckled one, and reached English through the Hindi 'cheeta'.
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