Q1. Green plants in the sea are useful for the respiration of fish because
(a) They give out oxygen
(b) They give out carbon dioxide
(c) The give out oxygen and carbon dioxide simultaneously
(d) They take oxygen and give out carbon dioxide
(UPSC Prelims, 1979)
Answer: (a) They give out oxygen
Explanation: Aquatic plants and algae perform photosynthesis, releasing oxygen into the water, which is essential for fish respiration. This process helps maintain oxygen levels in aquatic ecosystems, supporting marine life.
Q2. What is a continental shelf ?
(a) It is a part of the ocean which is really an extension of the land mass, but submerged
(b) It is that part where the ocean commences
(c) It is a land mass which is surrounded by water on all sides
(d) It is a part of the continent that is submerged in relatively shallow sea
Answer: (d) It is a part of the continent that is submerged in relatively shallow sea
Explanation: A continental shelf is the submerged extension of a continent, found in shallow seas, and is rich in marine resources.
Q3. A narrow strip of land, bordered on both sides by water, connecting to larger bodies of land is called
(a) Dune
(b) Equinox
(c) Isthmus
(d) Strait
(UPSC Prelims 1980)
Answer: (c) Isthmus
Explanation: An isthmus is a narrow land bridge connecting two larger land masses, bordered by water on both sides, such as the Isthmus of Panama.
Q4. Plankton refers to
(a) A kind of fish
(b) A submerged platform in waters
(c) Drifting of organisms in a body of water
(d) A kind of animal living under water
(UPSC Prelims 1982)
Answer: (c)
Explanation: Plankton are microscopic organisms that float or drift in water bodies, forming the base of aquatic food chains. They include phytoplankton (plants) and zooplankton (animals), crucial for marine ecosystems.
Q5. A new biofertiliser is
(a) Compost
(b) Farmyard manure
(c) Green blue algae
(d) Nitrates
(UPSC Prelims 1986)
Answer: (c) Green blue algae
Explanation: Green blue algae, also known as cyanobacteria, are used as biofertilisers because they fix atmospheric nitrogen and enrich the soil naturally. They are especially effective in paddy fields, promoting sustainable agriculture.