World Climate Zones & Biomes

• The five major climate zones of the world and what controls climate.
• Key biomes — what they are, where they are, what lives there.
• Link between climate → vegetation → wildlife.
• Why tropical rainforests are called the "lungs of the Earth."

What controls climate?

Major climate zones

Major biomes

1. Tropical Rainforest

• Where: Amazon Basin (South America), Congo Basin (Africa), SE Asia (Malaysia, Indonesia).
• Climate: Hot (27°C avg), very wet (200–400 cm rain/year), no dry season.
• Vegetation: Dense, multi-layered canopy; emergent trees (up to 60 m), canopy trees, understory, forest floor.
• Wildlife: Greatest biodiversity on Earth — jaguars, gorillas, orangutans, toucans, poison dart frogs.
• Importance: "Lungs of the Earth" — produces ~20% of world's oxygen; absorbs huge amounts of CO₂.
• Threat: Deforestation for farming, logging, cattle ranching (~17% of Amazon lost by 2020).

2. Savanna (Tropical Grassland)

• Where: Sub-Saharan Africa (most famous), South America (Cerrado, Llanos), northern Australia.
• Climate: Wet season + distinct dry season; 25–30°C.
• Vegetation: Tall grasses with scattered flat-topped trees (acacia, baobab).
• Wildlife: African savanna — Big Five (lion, elephant, buffalo, rhino, leopard); wildebeest migration.

3. Desert

• Where: Sahara (North Africa), Arabian, Thar (India/Pakistan), Gobi (Central Asia), Atacama (South America).
• Climate: < 25 cm rain/year; extreme day/night temperature swings; day up to 50°C, night near 0°C.
• Vegetation: Cacti (New World), succulents, thorny shrubs; sparse.
• Wildlife: Camels, fennec fox, rattlesnakes, kangaroo rats — all adapted to save water.
• Hot vs Cold deserts: Sahara = hot; Gobi = cold (freezes in winter).

4. Temperate Grassland

• Where: Prairies (North America), Steppes (Central Asia/Russia), Pampas (Argentina), Veld (South Africa).
• Climate: Semi-arid; cold winters, warm summers; seasonal rain.
• Vegetation: Grasses dominate; few trees (not enough rain).
• Wildlife: Bison (North America), wild horses, prairie dogs; now mostly converted to farmland.
• Importance: World's breadbasket — wheat, maize, soybean production.

5. Temperate Deciduous Forest

• Where: Western Europe, Eastern USA, Eastern China, Japan.
• Climate: Four seasons; 75–150 cm rain/year; mild.
• Vegetation: Broad-leaved trees that shed leaves in autumn — oak, maple, beech, birch.
• Wildlife: Deer, foxes, squirrels, owls, bears.

6. Boreal Forest / Taiga

• Where: Russia, Canada, Scandinavia — largest biome on Earth by area.
• Climate: Long, very cold winters (−50°C); short summers; low rainfall.
• Vegetation: Coniferous trees (pine, spruce, fir) — needle-shaped leaves reduce water loss.
• Wildlife: Moose, wolves, lynx, Siberian tiger, migratory birds.
• Importance: Huge carbon store; major source of timber.

7. Tundra

• Where: Arctic regions of Russia, Canada, Alaska; also high mountains (alpine tundra).
• Climate: Extremely cold (−30 to −20°C); permafrost (permanently frozen ground below surface); very little rain.
• Vegetation: Mosses, lichens, low shrubs, hardy grasses — no trees.
• Wildlife: Polar bears, Arctic fox, reindeer/caribou, snowy owls.
• Threat: Climate change is thawing permafrost → releasing stored methane → accelerating warming.

India's biomes

Conservation

• IUCN Red List: tracks endangered species globally.
• Biodiversity hotspots: areas with exceptional species richness and high threat — 36 globally; Western Ghats + Sri Lanka is one; Eastern Himalayas is another.
• Threats: Habitat loss, climate change, invasive species, over-hunting.

• Name five factors that affect climate.
• What is a biome? List three major biomes and their characteristic animals.
• Why are tropical rainforests called the "lungs of the Earth"?
• What is permafrost? Why is its thawing dangerous?
• Name two biodiversity hotspots in India.

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