Which one of the following statements with regard to growth of coral reefs is not correct?
- A.Coral can grow abundantly in freshwater.
- B.It requires warm water between 23 °C-25 °C.
- C.It requires shallow saltwater, not deeper than 50 metres.
- D.It requires plenty of sunlight to aid photosynthesis.
Correct answer
Explanation
The correct answer is A, Coral can grow abundantly in freshwater. Reef-building corals are marine animals and die in fresh water, so this statement is false.
Corals are tiny polyps that build skeletons of calcium carbonate and live with algae called zooxanthellae inside their tissues. The algae make food by photosynthesis, so the water must be clear, sunlit and shallow, usually less than about 50 metres deep. Corals also need warm water of roughly 20 °C to 28 °C, with the best growth around 23 °C to 25 °C, and normal sea salinity. This is why reefs do not form at the mouths of large rivers such as the Ganga, whose fresh, muddy water kills the polyps.
B is a correct statement because warm water near 23–25 °C is ideal for reef growth. C is a correct statement because shallow salt water lets sunlight reach the algae. D is a correct statement because the zooxanthellae need sunlight to photosynthesise and feed the coral.
Exam tip: Coral needs warm (about 20–28 °C), clear, shallow (under 50 m), salty, sunlit water; no reefs at muddy river mouths.
Practice Questions
View allWhich one of the following biosphere reserves is spread over three States in India?
- A.Nilgiri
- B.Achanakmar-Amarkantak
- C.Seshachalam
- D.Agasthyamalai
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The Nilgiri Biosphere Reserve spreads across Tamil Nadu, Kerala and Karnataka. Set up in 1986, Nilgiri was India's first biosphere reserve, and in 2000 it became the first Indian reserve on UNESCO's World Network of Biosphere Reserves.
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- A.2 only
- B.3 and 4
- C.1 and 3
- D.2 and 4
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- A.Vegetable remains
- B.Plastic materials
- C.Animal carcasses
- D.Wastes of flowers
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Read the full explanation →According to the Environmental Protection Agency (EPA), which one of the following is the largest source of sulphur dioxide emissions?
- A.Locomotives using fossil fuels
- B.Ships using fossil fuels
- C.Extraction of metals from ores
- D.Power plants using fossil fuels
Show answer
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- A.Plankton
- B.Periphyton
- C.Benthos
- D.Nekton
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