Topic 3: 3.1 Large-scale ecosystems — Edexcel GCSE Geography A
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Topic 3: 3.1 Large-scale ecosystems explained
Topic 3: 3.1 Large-scale ecosystems covers 2 specification points, including A.
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Distributions and characteristics of the… and B. The role of climate and local factors…. Open a point below for its explanation and revision guidance.
a. Distributions and characteristics of the world’s large-scale ecosystems (tropical, temperate and boreal forests, tropical and temperate grasslands, deserts and tundra).
This criterion asks where the world's large-scale ecosystems occur and what each is like. Their distribution follows climate, especially temperature and precipitation. Tropical forests lie near the equator; temperate forests lie in mid-latitudes; boreal forests form a belt poleward of them across the high northern hemisphere. Tropical grasslands (savanna) lie between forests and deserts, and temperate grasslands lie in continental interiors. Deserts, such as the Sahara, receive very little rain, and tundra lies in cold polar areas and on high mountains. Describe characteristics with evidence: tropical rainforest has tall, layered evergreen trees; boreal forest has coniferous trees; tundra has permafrost and low-growing vegetation. Name a location for each ecosystem you describe.
b. The role of climate and local factors (soils and altitude) in influencing the distribution of different large-scale ecosystems.
This criterion asks how climate and local factors (soils and altitude) influence ecosystem distribution. Climate, mainly temperature and precipitation, is the main control, creating broad latitudinal belts. Local factors modify this pattern. Altitude matters because temperature falls by roughly 6.5°C for every 1000 m of ascent, so mountain slopes can show a sequence of ecosystems similar to moving from the equator towards the poles. Soils matter because nutrients, depth, drainage and waterlogging determine which plants survive; poorly drained or nutrient-poor soils can limit tree growth even in wet climates. Always state the climate control first, then add the local factor.
Your focus
- Locate all seven named large-scale ecosystems on a world map.
- Describe one characteristic of each ecosystem using vegetation, climate or permafrost evidence.
- Match a given climate description to the correct large-scale ecosystem.
Show all 6 objectives
- Explain how climate controls the broad distribution of large-scale ecosystems.
- Calculate the approximate temperature drop over a given height difference using roughly 6.5°C per 1000 m.
- Describe how a named soil property influences which plants can grow in an ecosystem.
Topic 3: 3.1 Large-scale ecosystems exam tips
Marking Points
- Identifies tropical forests as lying near the equator, where temperatures and rainfall are high for much of the year.
- Places temperate forests in mid-latitudes, where seasonal change in temperature and rainfall occurs.
- Locates boreal forests poleward of temperate forests across the high northern hemisphere.
- Distinguishes tropical grasslands with wet and dry seasons from temperate grasslands with cold winters and warm summers.
- Describes deserts as areas of very low precipitation, using a named example such as the Sahara.
- Describes tundra as cold, largely treeless land with permafrost and low-growing vegetation.
- Explains that climate sets the broad distribution of ecosystems, with temperature and precipitation as the key variables.
- Links altitude to falling temperature, at roughly 6.5°C per 1000 m, and therefore to ecosystem zonation on mountains.
- Describes soil factors such as nutrient content, drainage and depth, and states how each affects plant growth.
- Recognises that local factors can modify but rarely override the broad climate-based pattern of ecosystems.
- Uses a clearly described example, such as a sequence of ecosystems up a mountain slope, to support the explanation.
Examiner Tips
- 💡Sketch a rough latitude sequence from equator to pole and place each ecosystem on it to check your answer.
- 💡Use any climate data in the question to match temperature and rainfall patterns to a single ecosystem before choosing.
- 💡Eliminate options that place an ecosystem in a climate it cannot survive in, then select the remaining option.
- 💡Structure each answer in two parts: first the climate control, then the local factor and how it changes the expected ecosystem.
- 💡Use the figure of roughly 6.5°C per 1000 m to quantify altitude effects when a question provides height data.
- 💡Check that any soil factor you choose affects plant growth directly, such as drainage, nutrient supply or depth.
Common Mistakes
- Treats all forests as tropical rainforests, ignoring temperate and boreal types; correct this by naming and describing each forest type separately.
- Confuses savanna with desert because both have sparse tree cover; correct this by stating that savanna receives seasonal rainfall that supports grass.
- Places tundra in tropical areas because it is cold at high altitude; correct this by linking tundra to polar climates and high mountain conditions.
- Attributes ecosystem variation to soil alone, ignoring climate; correct this by stating climate as the primary control and soil as a secondary factor.
- Assumes any high-altitude location must be tundra, ignoring latitude and how far the altitude lowers temperature; correct this by describing a zonation sequence that depends on both.
- Describes soils as fertile or poor without saying why; correct this by naming a specific soil property and its effect on plant survival or growth.