Why is the distribution of global biomes the way it is?
The global distribution and characteristics of major biomes and how they are controlled by climate; how local factors alter biome distribution; and how the biotic and abiotic components of biomes interact.
A focused answer to Edexcel GCSE Geography B Topic 7 (People and the biosphere) on global biomes, covering the distribution and characteristics of major biomes, how climate controls them, how local factors alter their distribution, and how the biotic and abiotic components of biomes interact.
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What this dot point is asking
This is Edexcel GCSE Geography B (1GB0) Paper 3, Section A (Topic 7, People and the biosphere). Edexcel expects you to know the global distribution and characteristics of the major biomes (tropical, temperate and boreal forests, tropical and temperate grasslands, deserts and tundra) and how their distribution is influenced by climate (temperature, precipitation, sunshine hours); how local factors (altitude, rock and soil type, drainage) alter the distribution locally; and how the biotic (flora, fauna) and abiotic (soils, rock, water, atmosphere) components of biomes interact. Climate graphs and world maps are common resources.
What a biome is
Climate controls the distribution
The single biggest control on where biomes are found is climate, especially temperature and precipitation, which are fixed by latitude through the global atmospheric circulation.
Sunshine hours and the angle of the Sun reinforce this, giving the tropics more energy for plant growth than the poles, which is why biodiversity and plant growth (productivity) are highest near the Equator and lowest towards the poles.
Local factors and interactions
The neat latitudinal pattern is modified at the local scale by several factors.
Altitude lowers temperature (so high mountains can have tundra-like conditions even in the tropics, and vegetation changes up a mountainside); rock and soil type affect fertility and what can grow (thin, acidic soils support different plants from deep, fertile ones); and drainage matters (waterlogged ground supports bog and marsh, while well-drained slopes support forest). These local factors explain why biome boundaries are not perfectly straight lines.
Within every biome, the biotic and abiotic components interact. Plants depend on the abiotic climate (sunlight, water, warmth) and soil; animals depend on the plants for food and habitat; and the living things in turn affect the abiotic environment (vegetation adds nutrients to the soil and influences the local climate). This interdependence means a change to one part affects the whole system.
Try this
Q1. Name three major global biomes. [1 mark]
- Cue. Any three of tropical rainforest, temperate forest, boreal forest (taiga), tropical grassland (savanna), temperate grassland, hot desert or tundra.
Q2. Explain why tropical rainforests are found near the Equator. [3 marks]
- Cue. Near the Equator, rising air under the global circulation gives high temperatures and heavy year-round rainfall, providing the constant warmth and water that allow dense, fast-growing forest with high biodiversity.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel B 20194 marksExplain how climate influences the global distribution of biomes. (Paper 3, Section A)Show worked answer →
A 4-mark "Explain" question on Paper 3 (People and the biosphere), assessing AO1 and AO2. Markers reward a chain from climate to biome location.
Award credit for: temperature and precipitation are the main controls. Near the Equator, high temperatures and heavy rainfall all year support dense tropical rainforest; around 30 degrees, sinking dry air gives hot deserts with little vegetation; in mid-latitudes, moderate temperatures and rainfall give temperate forest and grassland; at high latitudes, cold temperatures and low precipitation give boreal forest (taiga) and then tundra. Because global atmospheric circulation fixes these climate belts by latitude, the biomes form roughly latitudinal bands. The strongest answers link specific temperature and rainfall conditions to a named biome and to the global circulation.
Edexcel B 20224 marksUsing Figure 1, describe the climate of the biome shown and explain how it suits the vegetation. (Paper 3, Section A)Show worked answer →
A 4-mark data-response question assessing AO4 (skills) and AO2. It combines reading a climate graph with explanation.
Award credit for: reading the climate graph accurately (for example a tropical rainforest with high temperatures around 26 to 28 degrees Celsius all year and high rainfall every month, totalling over 2000 mm) and quoting figures. Then explain how this suits the vegetation: constant warmth and abundant water allow rapid, year-round plant growth, dense layered forest and high biodiversity, with adaptations such as drip-tip leaves to shed heavy rain. Markers reward accurate reading and quoting of the graph plus a linked explanation connecting the climate to the vegetation.
Related dot points
- How the biosphere provides goods and services for local people and is exploited commercially; how it regulates the atmosphere, soils and water; rising demand for food, water and energy; and the theories of Malthus and Boserup on population and resources.
A focused answer to Edexcel GCSE Geography B Topic 7 (People and the biosphere) on the biosphere's goods and services, how it regulates the atmosphere, soils and water, the rising demand for food, water and energy, and the contrasting theories of Malthus and Boserup on population and resources.
- The structure, functioning and adaptations of the tropical rainforest and the taiga: how biotic and abiotic components are interdependent, how plants and animals are adapted, and the contrasting rates of nutrient cycling, productivity and biodiversity.
A focused answer to Edexcel GCSE Geography B Topic 8 (Forests under threat) on the tropical rainforest and taiga, covering their structure and functioning, how biotic and abiotic components are interdependent, plant and animal adaptations, and the contrasting rates of nutrient cycling, productivity and biodiversity.
- The direct and indirect threats to the tropical rainforest (deforestation and climate change) and to the taiga (logging, mineral and fossil-fuel exploitation, acid rain, fire, pests and disease) and their impacts on biodiversity.
A focused answer to Edexcel GCSE Geography B Topic 8 (Forests under threat) on the direct and indirect threats to the tropical rainforest (deforestation and climate change) and the taiga (logging, mineral and fossil-fuel exploitation, acid rain, fire, pests and disease), and their impacts on biodiversity.
- Global atmospheric circulation and ocean currents redistribute heat; natural causes explain past climate change over the Quaternary, evidenced by ice cores, tree rings and historical sources.
A focused answer to Edexcel GCSE Geography B Topic 1 (Hazardous Earth) on global atmospheric circulation, ocean currents and the natural causes of climate change, covering how circulation cells locate arid and wet zones and how ice cores, tree rings and historical sources evidence Quaternary climate change.
- Global actions to protect tropical rainforests (CITES, REDD), the challenge of sustainable forest management and alternative livelihoods, and the challenges and conflicts of protecting the taiga wilderness.
A focused answer to Edexcel GCSE Geography B Topic 8 (Forests under threat) on conservation and sustainable management, covering global actions to protect tropical rainforests (CITES, REDD), the challenge of sustainable management and alternative livelihoods, and the conflicts over protecting the taiga wilderness.
Sources & how we know this
- Pearson Edexcel GCSE (9-1) Geography B (1GB0) specification — Pearson Edexcel (2016)