IGCSE Geography / Rural environments

Biomes and what controls them revision notes

Edexcel International GCSE Geography (4GE1), chapter 5: Rural environments, specification point 5.1a, 5.S1. Free lesson.

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A biome is a very large ecosystem with its own climate and vegetation. Biomes form broad bands because latitude affects temperature and rainfall, while local factors can change the pattern.

What makes an area a biome?

A biome is a very large ecosystem. It includes a community of plants and animals, together with the climate and soil they live in. The key features are its large scale, a shared climate and a shared type of vegetation. A tropical forest is a biome. A single wood is an ecosystem, but it is not large enough to be a biome.

Where the seven biomes are found

The seven biomes lie in broad bands that run from east to west. Start at the Equator and work outwards. The order reflects how climate and vegetation change with distance from the Equator. Tropical forest lies along the Equator, from 23.5°N to 23.5°S. The Amazon is an example. Tropical grassland, also called savanna, lies on either side of tropical forest, including central Africa and northern Australia. Desert lies further out, where conditions are dry. The Sahara is an example. Temperate grassland is found deep inside continents, including the prairies and steppes.…

How latitude controls the bands

Latitude is distance north or south of the Equator. It affects the Sun's angle, which changes temperature and rainfall. Plants need warmth and water, so these climate differences lead to different biomes. Near the Equator, the Sun is high overhead, so its energy is concentrated on a small area. It is hot all year. Near the poles, the Sun is low in the sky, so the same energy spreads over a larger area. It is cold, with long winters. Hot air at the Equator rises, cools and brings heavy rain. Cold polar air holds very little moisture, so there is little rainfall. This helps explain the…

How local factors change the pattern

Latitude controls the broad pattern, but three other factors can bend the bands. Each changes the climate, which then changes the vegetation. Altitude is height above sea level. It gets colder as you climb, so tundra plants can grow near the top of a high mountain, even in the tropics. Distance from the sea affects temperature and rainfall. Inland areas are drier, with hotter summers and colder winters, so grassland can replace forest. Ocean currents affect nearby coasts. A warm current makes the coast milder and wetter. A cold current cools the air, so less rain falls and the…

How to answer biome map questions

For a question asking you to explain a pattern, include evidence from the map and then give the reason. A statement about latitude on its own does not show that you have used the map. For example, tropical forest lies along the Equator on the map. The Sun is overhead there, so it is hot and wet all year. For a question asking you to describe a distribution, say where the biome is. Do not add reasons if the question only asks for a description. Boreal forest forms a belt across the northern continents, between 50°N and 60°N. It crosses Canada and Siberia.