What a biome is at Higher Level: The same ideas as SL, with different examples: rainforest on three continents, hummingbirds and sunbirds, and a biome map of Africa. HL goes on to the three climate patterns behind the biomes (2.4.8).
Practise this as you read
- Define a biome in its two parts.
- Explain why far-apart ecosystems look alike.
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One climate, one kind of ecosystem: A biome is a group of ecosystems that look alike because they grew up in the same kind of climate.
Climate works through three things: how much rain falls, how warm it is, and the insolation. Together they decide how much water and energy plants get, so they decide which plants grow.
The points to remember
- An ecosystem is a community of living things and its physical surroundings, in one place.
- A biome groups many comparable ecosystems that developed in similar climatic conditions.
- The same biome occurs wherever that climate occurs, even on different continents.
- Precipitation, temperature and insolation are the major influences on land biomes.
- A biome is named after its main vegetation: tropical rainforest, taiga, savanna, hot desert.
Remember it as: Same climate, same kind of ecosystem, anywhere on Earth.
Real example: tropical rainforest grows in the Amazon, the Congo Basin and Borneo, on three continents. All three lie near the equator, are hot (about 27 °C) and wet (over 2,000 mm a year) all year, and have tall evergreen trees in layers.
Two parts to the definition: 'A biome is a large area' is not enough. Say both parts: a group of comparable ecosystems, and developed in similar climatic conditions.
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Why do biomes on different continents look alike? The same conditions favour the same solutions, even in species that are not related.
Parallel features
- Ecosystems in similar conditions have many parallel features, even when they are far apart.
- The species are usually different, but they look and live alike.
- The same conditions favour the same features, such as water-storing stems in deserts.
- So a biome shares a structure (layers, plant forms), not a list of species.
Hummingbirds (the Americas)
- Long, thin beak
- Feeds on flower nectar
- Bright, shiny feathers
Sunbirds (Africa and Asia)
- Long, thin beak
- Feeds on flower nectar
- Bright, shiny feathers
Real example: hummingbirds live only in the Americas and sunbirds only in Africa and Asia. They are not closely related, but the flowering tropical forests they live in have given both long beaks for nectar.
Papers often start with a biome or vegetation map of the case-study country. The first question is usually a one-mark reading: name a biome from the map.
Reading a biome map
- Match each colour to the key before you answer.
- Most widespread = the biome covering the largest area.
- Give the full name from the key: 'boreal forest (taiga)', not just 'forest'.
- Write one answer: when several are given, only the first is marked.
Real example: in Africa savanna covers more land than any other biome. It lies on both sides of the rainforest of the Congo Basin, with the Sahara to the north and the Kalahari and Namib to the south.
Use the key's words: 'Forest' alone, or 'rainforest' when the key says 'subtropical rainforest', does not earn the mark. Copy the biome's full name from the key.
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How this comes up: Paper 1, question 1(a): a biome map in the resource booklet. Identify the most widespread biome [1].
Figure 1 shows a simplified biome map of Africa.
With reference to Figure 1, identify the most widespread biome in Africa.
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