Ecology & ecosystems

Answer: (d) Aquatic plants absorb heavy metals and excess nutrients.

The kidney comparison is about purification: kidneys filter waste out of blood, and wetlands filter pollutants out of water. Option (d), aquatic plants absorbing heavy metals and excess nutrients, is the function that does this cleaning job.

• ✓ (d) Wetlands are called the earth's kidneys because they filter pollutants. Wetland plants take up heavy metals, and plant roots and microbes absorb excess nutrients from fertilizer, manure and sewage.
• ✗ (a) Runoff, percolation and evaporation describe how water moves through a wetland. This is the water cycle, not the removal of wastes.
• ✗ (b) Algae as the base of the food chain is a habitat and food-web function, closer to a 'nursery' role than to a kidney's cleaning role.
• ✗ (c) Sediment balance and soil stabilisation are physical, erosion-control functions. They do not purify water the way kidneys do.

Remember · Wetlands = kidneys of the landscape: they filter and purify water, with plants trapping heavy metals, pesticides and excess nutrients.

Question and answer: UPSC's official GS Paper I (2022, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (a) 1, 3 and 4 only

Only alfalfa, chickpea and clover fix nitrogen, because they are legumes. Legume roots carry nodules housing Rhizobium bacteria that turn nitrogen from the air into a form the plant can use. Amaranth, purslane and spinach are not legumes.

• ✓ 1. Alfalfa (lucerne) is a legume with its own Rhizobium partner, Rhizobium meliloti, in nodules on its roots.
• ✗ 2. Amaranth is a leafy green and grain crop, not a legume, so it has no Rhizobium root nodules.
• ✓ 3. Chickpea (gram) is a pulse and a legume crop, so its root nodules host nitrogen-fixing Rhizobium.
• ✓ 4. Clover is a legume; its roots form nodules with Rhizobium bacteria (the clover group).
• ✗ 5. Purslane (kulfa) is a leafy vegetable, not a legume, and does not fix nitrogen.
• ✗ 6. Spinach is a leafy vegetable, not a legume, and does not fix nitrogen.

Remember · Nitrogen fixers here are legumes: alfalfa, chickpea, clover. Rhizobium in root nodules does the fixing. Leafy greens such as spinach, amaranth and purslane are not legumes.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 5 (practise this chapter)

Question and answer: UPSC's official GS Paper I (2022, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (a) Restoration of damaged coral reefs

Biorock technology is used to restore damaged coral reefs. A low-voltage electric current is passed through seawater between a submerged metal frame and an anode, so that minerals in the water deposit as limestone on the frame, and corals attached to it grow quickly.

• ✓ (a) With an anode and a cathode in sea water and a current between them, calcium and carbonate ions combine and stick to the cathode structure as calcium carbonate; corals adhere to it and grow fast. The UN has cited biorock artificial reefs as successful in certain areas.
• ✗ (b) Biorock is not a plant-residue building material; it is limestone grown from seawater minerals on an electrified frame.
• ✗ (c) Nothing in Biorock concerns locating or extracting shale gas.
• ✗ (d) Biorock has no link to salt licks for forest animals; it is an undersea technology.

Remember · Biorock (mineral accretion): low-voltage current in seawater grows limestone on metal frames, letting corals attach and recover. Used to restore reefs.

Question and answer: UPSC's official GS Paper I (2022, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (c) Creation of mini forests in urban areas

The Miyawaki method is famous for creating dense mini forests in urban areas. Named after Japanese botanist Akira Miyawaki, it plants saplings of many native species very close together so that they grow into a thick forest in a few years.

• ✓ (c) Saplings of various species are planted close to each other and grow into a dense urban forest, ten times faster and thirty times denser than by the traditional method, according to the Prime Minister's Office.
• ✗ (a) The method makes forests, not commercial farms, and it is not a dryland-farming scheme.
• ✗ (b) It uses mixed native tree species, not genetically modified plants.
• ✗ (d) It has no connection to wind energy.

Remember · Miyawaki method (Akira Miyawaki, Japan): close planting of many native species to raise dense mini urban forests within 2-3 years.

Question and answer: UPSC's official GS Paper I (2022, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink · Report an error

Answer: (a) Ant

Ants are the well-known fungus farmers among these options. The fungus-gardening (attine) ants, including leafcutter ants of the American tropics, grow fungus in their nests as their food.

• ✓ (a) Attine ants, more than 250 species, cultivate fungi as their main food. Leafcutter ants cut leaves, carry them into underground nests and use them to feed the fungus.
• ✗ (b) Cockroaches are not known as fungus cultivators.
• ✗ (c) Crabs are not known as fungus cultivators.
• ✗ (d) Spiders are not known as fungus cultivators.

Remember · Fungus-growing (attine) ants, such as leafcutter ants, farm fungus in their nests as food. This is an example of mutualism between an insect and a fungus.

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