UPSC Prelims 2022 Q43: Environment & Ecology – Water & Wetland Conservation
- (a) The water cycle in wetlands involves surface runoff, subsoil percolation and evaporation.
- (b) Algae form the nutrient base upon which fish, crustaceans, molluscs, birds, reptiles and mammals thrive.
- (c) Wetlands play a vital role in maintaining sedimentation balance and soil stabilization.
- (d) Aquatic plants absorb heavy metals and excess nutrients.
Answer: (d) Aquatic plants absorb heavy metals and excess nutrients.
Explanation
Wetlands as the 'kidneys' of the Earth
Kidneys filter the blood, removing toxins and excess salts.
So the analogy points to the filtering and purifying role of wetlands.
| Option | Function described | Matches 'kidney'? |
|---|---|---|
| (a) Runoff, percolation, evaporation | Water cycle movement | No |
| (b) Algae as nutrient base | Food web support | No |
| (c) Sediment balance, soil stabilisation | Erosion control | No |
| (d) Plants absorb heavy metals and excess nutrients | Filtration and detoxification | Yes |
Wetland plants such as reeds, cattails and water hyacinth take up nitrates, phosphates and heavy metals.
This natural cleaning is called phytoremediation.
Answer: (d) Aquatic plants absorb heavy metals and excess nutrients.
Why each option is right or wrong
- (a) Incorrect. The water cycle is about moving water, while kidneys clean the fluid that passes through them.
- (b) Incorrect. Algae supporting a food web is a productivity role, not a filtering role.
- (c) Incorrect. Sediment balance is physical erosion control; it does not remove toxins from water.
- (d) CORRECT. Plants absorbing heavy metals and excess nutrients mirrors how kidneys filter toxins from blood.
Key point
Wetlands are 'kidneys' because they filter water: plants absorb heavy metals and excess nutrients.
Remember
Wetland = kidney = filter; the answer is plants absorbing heavy metals and nutrients.
Common mistakes
- Picking the water cycle option because it mentions water, though kidneys filter rather than move fluid.
- Choosing sediment trapping, which is useful but is a physical, not a purifying, function.
- Mixing the 'lungs' analogy (oxygen and carbon exchange) with the 'kidneys' analogy (filtration).
Exam tip
In analogy questions, name the organ's single core job first. Kidney = filter; lungs = gas exchange; then pick the option doing that job.
Sources
- Ramsar Convention Secretariat — Wetland Ecosystem Services
- NCERT Class XII — Biology, Ch 14 (Ecosystem)