World Biomes and Biodiversity

Why Biomes and Biodiversity Matter for NDA

Geography is a high-scoring slice of the NDA General Ability Test, and questions on natural vegetation, biomes and biodiversity appear almost every year. They ask you to match a biome to its climate, name its typical trees or animals, or identify a biodiversity hotspot. These answers are objective and never change, so a few clear facts per biome earn easy, reliable marks.

The key skill is seeing biomes as a chain of cause and effect: climate → soil → plants → animals. Once you understand that temperature and rainfall decide which plants grow, and that plants decide which animals can live there, the whole topic becomes logical instead of pure memorisation. The same chain explains why people farm, herd or hunt differently in each region.

This topic also connects to many other chapters — climate, soils, agriculture and even population distribution all flow from it. So the effort you spend here pays off across the entire Geography section, not just on direct questions.

Key Terms You Must Get Right

NDA often tests definitions directly, so fix these words first. Keep them distinct in your mind — examiners deliberately mix them up in options.

• Biome: a large land or water region with a characteristic climate, vegetation and animal life (e.g. tropical rainforest).
• Ecosystem: a community of living organisms interacting with their non-living environment (air, water, soil) in any area, large or small.
• Biosphere: the thin zone of the Earth where life exists — the meeting of land (lithosphere), water (hydrosphere) and air (atmosphere).
• Biodiversity: the total variety of living organisms — the number and variety of species, their genes and their ecosystems.
• Habitat: the natural home of a particular species.

How Climate Shapes Every Biome

Two factors decide which biome forms in a place: temperature (set mainly by latitude and altitude) and rainfall (set by winds, ocean currents and relief). Together they decide what plants can survive, and the plants then support the animals.

• Hot and wet → dense evergreen forests (equatorial regions).
• Hot with a dry season → grasslands with scattered trees (savanna).
• Hot and very dry → deserts with thorny, drought-resistant plants.
• Cold → coniferous forests, then treeless tundra near the poles.

As you climb a high mountain you pass through these same belts in miniature — tropical forest at the foot, then temperate forest, then coniferous forest, alpine meadow and finally snow. This is called altitudinal zonation, and it mirrors the change you would see travelling from the equator to the pole.

Tropical Rainforest (Equatorial) Biome

Found near the equator (0°–10° N and S) — the Amazon basin, Congo basin and Indonesia. It is hot all year (about 27°C) with very heavy rainfall (over 200 cm), so growth never stops.

• Vegetation: dense, multi-layered evergreen forest; tall hardwoods like mahogany, ebony and rosewood; lianas and epiphytes.
• Animals: monkeys, sloths, jaguars, parrots, snakes and countless insects.
• Feature: the richest biome in biodiversity on Earth, often called the "lungs of the Earth" for its oxygen output.

Savanna and Temperate Grassland Biomes

Grasslands form where rainfall is too low for forest but enough to stop desert. There are two main types — learn both, as NDA loves their regional names.

Tropical grassland (Savanna)

• Found between the rainforest and the deserts (e.g. East Africa, Brazil's Campos, Venezuela's Llanos).
• Tall grass with scattered drought-resistant trees like acacia; a clear wet and dry season.
• Home to large grazing herds — zebra, giraffe, elephant — and predators like lions; called the "big-game country".

Temperate grassland

• Found in mid-latitude continental interiors with hot summers and cold winters.
• Regional names: Prairies (N. America), Pampas (Argentina), Steppes (Eurasia), Velds (S. Africa), Downs (Australia).
• Short, nutritious grass and almost no trees; these are the world's great wheat belts and cattle ranches.

Desert Biome

Deserts form where annual rainfall is below 25 cm. They lie mainly around 20°–30° latitude (hot deserts) or in cold continental interiors (cold deserts).

• Hot deserts: Sahara, Thar, Arabian, Kalahari — very hot days, cold nights, extreme dryness.
• Cold deserts: Gobi, Ladakh, Patagonia — dry but very cold.
• Vegetation: sparse, drought-resistant xerophytes — cacti, thorny bushes, with deep roots, waxy skins and spines to save water.
• Animals: camels, desert foxes, lizards, snakes and scorpions, mostly active at night.

Temperate Forest and Coniferous (Taiga) Biomes

Moving towards the poles, forests change with the falling temperature. NDA tests the difference between these mid-latitude and high-latitude forests.

Temperate deciduous forest

• Mid-latitudes with warm summers and cold winters (Western Europe, eastern USA, China).
• Broad-leaved trees — oak, ash, beech, elm — that shed leaves in autumn to survive winter.

Coniferous forest (Taiga / Boreal)

• A broad belt across high-latitude Eurasia and North America (just south of the tundra).
• Evergreen conifers — pine, fir, spruce — with needle leaves and a cone shape that sheds snow.
• Softwood timber from here supplies the world's paper and pulp industry.

Tundra and Mediterranean Biomes

Two more biomes complete the world picture — the frozen tundra near the poles and the mild Mediterranean lands of the west coasts.

Tundra biome

• The coldest land biome, around the Arctic Ocean (and high mountains as alpine tundra).
• No trees; only mosses, lichens and small shrubs grow in the short summer over frozen permafrost.
• Animals: reindeer, polar bear, Arctic fox, seals; few species but specially adapted.

Mediterranean biome

• Found on west coasts around 30°–40° latitude (the Mediterranean Sea, California, central Chile, SW Australia, the Cape).
• Hot dry summers and mild wet winters; trees with thick bark and waxy leaves.
• Famous for orchards of citrus, olives, grapes and figs — the "Garden of the world".

Biodiversity: Three Levels and India's Place

Biodiversity is studied at three levels — remember all three, as NDA asks them directly.

• Genetic diversity: variety of genes within a single species (e.g. many varieties of rice or mango).
• Species diversity: the variety of different species in a region.
• Ecosystem diversity: the variety of habitats — forests, wetlands, deserts, coral reefs — in an area.

India is one of the world's 17 mega-diverse countries, holding nearly 8% of all recorded species on just about 2.4% of the land area. India also has four biodiversity hotspots: the Himalayas, Western Ghats & Sri Lanka, Indo-Burma, and Sundaland (Nicobar Islands). A hotspot is a region rich in species but under serious threat of loss. The term was coined by Norman Myers, and to qualify a region must have at least 1,500 endemic plant species and have lost most of its original natural vegetation. The Western Ghats, for instance, host hundreds of frogs, fish and flowering plants found nowhere else on Earth, which is exactly why their protection is treated as urgent.

Threats and Conservation of Biodiversity

Biodiversity is shrinking fast. The main threats are habitat loss, deforestation, pollution, over-hunting, and invasive species. To protect it, two approaches are used — learn the difference, as it is a common one-mark question.

• In-situ conservation: protecting species in their natural home — national parks, wildlife sanctuaries, biosphere reserves.
• Ex-situ conservation: protecting species away from their home — zoos, botanical gardens, seed banks and gene banks.

Key Indian efforts include Project Tiger (1973), Project Elephant, and the network of biosphere reserves such as Nilgiri and Nanda Devi. Globally, the IUCN Red List classifies species as endangered, vulnerable or extinct, and the Convention on Biological Diversity (1992, Rio Earth Summit) set the framework for protection.

It helps to remember why conservation matters beyond just saving animals. Biodiversity gives us food, medicine, timber and clean water, keeps soil fertile, pollinates crops and balances the climate — these are called ecosystem services. When a species disappears, that loss is permanent and can upset an entire food chain. A biosphere reserve is special because it protects whole ecosystems, not just single species, dividing land into a strictly guarded core zone, a buffer zone and a transition zone where people may live and farm sustainably.

Worked Example: Identify the Biome

NDA often describes a region and asks you to name its biome. Work through the clues step by step instead of guessing.

Notice how each clue removed wrong options. Vegetation type fixes forest vs grassland, the season pattern fixes tropical vs temperate, and the animals confirm it. Train yourself to read clues in this order and biome questions become quick marks.

Previous-Year Question and Quick Recap

Keep your facts tied to the cause-and-effect chain — climate → vegetation → animals — and most questions will answer themselves.