Key Idea: Most marks in topic 2.4 come from reading climate graphs and biome maps and explaining where biomes are. Learn those first, then the tricellular model.
1. Where biomes are (most marks)
- Temperature and precipitation decide which terrestrial biome forms.
- Insolation depends on latitude; altitude makes places colder.
- On a biome graph, find the rainfall and temperature, then read the biome.
- Name the limiting factor: too cold, too dry, or too little light.
2. Climate graphs and biomes
- Climate is the average over about 30 years; weather is the short term.
- Temperature range = warmest month minus coldest month, with units.
- Six groups: freshwater, marine, forest, grassland, desert, tundra.
- Learn two features of each: climate, plants, soil, productivity.
3. Air and oceans move heat
- Tricellular model: Hadley, Ferrel and polar cells move air and heat.
- Air rises at the equator, cools and gives heavy rain: rainforest.
- Air sinks at about 30° north and south, so it is dry: hot deserts.
- Ocean currents carry heat too: the Gulf Stream keeps western Europe mild.
How it is examined:
| Question | How to score |
|---|---|
| [1] Identify a biome or vegetation from a map | Match the colour to the key and copy the name in full. |
| [1] State a range or month from a climate graph | Read the bars and the line carefully; give units. |
| [2] Distinguish two climates from climate graphs | One point on temperature, one on rainfall, each with both places. |
| [4] Identify four features of a named biome | Climate, plants, soil and productivity: one feature each. |
| [4] Outline how the tricellular model explains biomes | Rising air, rain, rainforest; sinking air, dry, desert. |
Key terms, one line each:
| Term | In one line |
|---|---|
| Climate | the average atmospheric conditions of a place over about 30 years |
| Weather | the state of the atmosphere over hours or days |
| Biome | a group of similar ecosystems that developed in similar climates |
| Insolation | the amount of the Sun's energy reaching the ground |
| Tricellular model | three cells of air in each hemisphere that move heat and rain |
| Ocean current | a large, steady flow of seawater that carries heat around the world |
Last-minute check: answer, then tap to see.
Which two abiotic factors most decide a terrestrial biome? Temperature and precipitation.
Why are hot deserts found near 30° north and south? Air sinks there, warms and stays dry.
How long is climate averaged over? About 30 years.
Why is western Europe milder than Canada at the same latitude? The Gulf Stream brings warm water.
Name two features of the tundra biome. Very cold with a short summer; low productivity and frozen soil.
Manaus in Brazil lies near the equator in rainforest; In Salah in Algeria lies near 27°N in hot desert. Outline how the tricellular model explains the difference in rainfall between the two places.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Exam tips
- On a map, match the colour to the key and copy the name exactly.
- On a climate graph, bars are rainfall and the line is temperature: check the axes.
- In a distinguish answer, use 'whereas' and give both places in each point.
- For a biome's location, name the factor: temperature, rainfall or insolation.