Climate & atmosphere

Answer: (c) Both 1 and 2

Both statements are correct: winds push warm surface water to the western side of tropical oceans, while in the temperate zone the westerlies carry warm water to the eastern side, that is, to the west coasts of continents.

• ✓ 1. In the tropics the easterly trade winds push warm water west and hold it there, so the western side of an ocean is warmer than the east. This matches warm currents along the east coasts of continents in tropical latitudes and cool waters off their west coasts.
• ✓ 2. Ocean circulation follows the planet's wind pattern, and in the middle latitudes the surface winds are the westerlies, which carry warm water eastwards, so the eastern side of the ocean is the warm side. NCERT notes that west coasts of continents in middle and higher latitudes are bordered by warm waters, as in north-western Europe.

Remember · Tropics: trade winds pile warm water in the west of the ocean. Temperate zone: westerlies carry warm water to the east, so west coasts of continents there are mild.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 13 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 13 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 13 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 9 (practise this chapter)

Question and answer: UPSC's official GS Paper I (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error

Answer: (c) 2, 3 and 4

Why not the tempting option · UPSC's key is (c). The general checks on tree growth in savannas are fire, grazing and browsing animals, and the long dry season of a seasonal-rainfall climate — a university biome guide puts it as frequent fires and large grazing mammals killing seedlings, with climate the most important factor. Soil does shape the tree–grass balance locally (thin or poorly drained soils carry no trees in some East African savannas), but the question asks for the general conditions and no option pairs soil with fire and grazing; termites build the mounds on which trees grow rather than checking them. In the exam, pick the option that holds the two universal controls, fire and grazing, together.

Fire, grazing and browsing animals, and the long dry season of a seasonal-rainfall climate are the recognised checks that keep savannas open and stop them turning into forest, so 2, 3 and 4 is the answer.

• ✗ 1. Termites are decomposers that break down about 30 per cent of dead organic matter; in parts of East Africa trees grow only on termite mounds, so termites aid rather than check tree growth. Burrowing animals are not a recognised control.
• ✓ 2. Wildfire is an important part of savanna ecosystems in all regions; annual burning of dry grass and litter helps keep woody plants from taking over.
• ✓ 3. Browsing and grazing animals alter the balance between trees and grass. Rising elephant numbers in Virunga National Park, for example, destroyed woody plants and turned a heavily wooded savanna into grass savanna with very few trees.
• ✓ 4. Savanna is a vegetation type of hot, seasonally dry climates: a long dry season each year limits tree growth and keeps the grass cover open.
• ✗ 5. Soil shapes the tree–grass balance only locally — thin or poorly drained soils carry no trees in some savannas — so it is not one of the general checks, and no option pairs it with fire and grazing.

Remember · Savannas stay open through fire, grazing and browsing animals, and a long dry season; without these, woody plants tend to spread and the savanna turns to forest.

Question and answer: UPSC's official GS Paper I (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink · Report an error