What are ecosystems and how are biomes distributed?
The structure of ecosystems (producers, consumers, decomposers, food chains and webs, nutrient cycling); and the global distribution of the major biomes, including tropical rainforest and polar, and the climatic conditions that create them.
A focused answer to OCR GCSE Geography B (J384) Sustaining Ecosystems on the structure of ecosystems, food chains, webs and nutrient cycling, and the global distribution of biomes such as tropical rainforest and polar.
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What this dot point is asking
This is OCR GCSE Geography B (J384) Component 1, Our Natural World, the opening enquiry of Sustaining Ecosystems: "What are ecosystems and how are biomes distributed?" OCR expects you to describe the structure of an ecosystem (producers, consumers, decomposers, food chains and webs, nutrient cycling) and to explain the global distribution of the major biomes, including tropical rainforest and polar, and the climatic conditions that create them. This sets up the detailed study of the rainforest and a polar environment.
The structure of an ecosystem
The living parts are grouped by how they get their energy.
- Producers are green plants that make their own food from sunlight by photosynthesis. They form the base of every ecosystem.
- Consumers eat other organisms: primary consumers (herbivores) eat plants, and secondary and tertiary consumers (carnivores) eat other animals.
- Decomposers (bacteria and fungi) break down dead plants and animals, releasing their nutrients back into the soil.
Energy flow and nutrient cycling
Energy and nutrients move through the ecosystem differently, and OCR wants you to keep them distinct.
The global distribution of biomes
The pattern runs by latitude:
- Tropical rainforest lies along the Equator, where rising air brings constant heat and heavy rain, supporting the most productive biome on Earth.
- Hot desert lies at about 30 degrees north and south, under the sinking, dry air of the Hadley cell.
- Temperate grassland and deciduous forest lie in the mid-latitudes, with moderate temperatures and rainfall.
- Polar and tundra lie at high latitudes and the poles, where very low temperatures and little precipitation limit life to hardy, low-growing species.
Try this
Q1. Describe the role of decomposers in an ecosystem. [2 marks]
- Cue. They break down dead plants and animals, releasing nutrients back into the soil for plants to reuse.
Q2. Explain why tropical rainforest is found along the Equator. [3 marks]
- Cue. Rising air at the Equator brings constant high temperatures and heavy rainfall, ideal for the rapid plant growth that supports the rainforest.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20184 marksExplain how energy and nutrients move through an ecosystem. (Component 1)Show worked answer →
A 4-mark "Explain" question assessing AO1 and AO2 of ecosystem structure. Markers reward a linked flow.
Award credit for: producers (green plants) capture energy from the Sun by photosynthesis and store it; primary consumers (herbivores) eat the producers, and secondary and tertiary consumers (carnivores) eat them, passing energy along a food chain (only about 10 percent passes to the next level). When plants and animals die, decomposers (bacteria and fungi) break them down, releasing nutrients back into the soil to be taken up by plants again. Top answers link the flow of energy (one-way, from the Sun) and the cycling of nutrients (recycled) rather than just listing the parts.
OCR 20216 marksExplain why the distribution of biomes is closely linked to climate. (Component 1)Show worked answer →
A 6-mark question marked by levels of response, assessing AO1 and AO2 of the climate-biome link.
Strong answers explain that climate, especially temperature and rainfall, controls which plants can grow, and plants form the base of each biome. They link the global atmospheric circulation to the pattern: rising air and heavy rain at the Equator support tropical rainforest; sinking, dry air at about 30 degrees gives hot desert; high latitudes with very low temperatures and little precipitation give polar and tundra; temperate latitudes give grassland and deciduous forest. A good answer names several biomes, links each to its temperature and rainfall, and connects the pattern back to the circulation. Markers reward the explained link rather than a list of biomes.
Related dot points
- The climate, soils, structure, biodiversity and nutrient cycling of the tropical rainforest; plant and animal adaptations; the causes and impacts of deforestation; and sustainable management at different scales.
A focused answer to OCR GCSE Geography B (J384) Sustaining Ecosystems on tropical rainforests, covering their climate, structure, adaptations and nutrient cycle, the causes and impacts of deforestation, and sustainable management.
- The climate, soils and ecosystem of polar and tundra environments; plant and animal adaptations; the opportunities and challenges for human activity; and the threats, including climate change, and sustainable management.
A focused answer to OCR GCSE Geography B (J384) Sustaining Ecosystems on polar and tundra environments, covering their climate, adaptations, the opportunities and challenges for people, and the threats from climate change.
- Why ecosystems matter (goods and services) and why they are under threat; and how local and global strategies, including protected areas, international agreements and balancing development with conservation, can manage biomes sustainably.
A focused answer to OCR GCSE Geography B (J384) Sustaining Ecosystems on managing ecosystems sustainably, covering why ecosystems matter, the threats they face, and local and global strategies including protected areas and international agreements.
- The structure of the atmosphere and the three-cell global circulation model; how pressure belts and surface winds create the global distribution of arid and humid zones; and how circulation links to extreme weather such as drought.
A focused answer to OCR GCSE Geography B (J384) Global Hazards on the global circulation of the atmosphere, the three-cell model, how pressure belts create deserts and rainforests, and how circulation drives extreme weather and drought.
- The evidence for climate change in the Quaternary period; the natural causes (orbital cycles, sunspots, volcanic activity) and the human enhanced greenhouse effect; the impacts of climate change; and how it can be managed through mitigation and adaptation.
A focused answer to OCR GCSE Geography B (J384) Changing Climate, covering evidence from the Quaternary, natural causes such as orbital cycles and volcanic activity, the human enhanced greenhouse effect, impacts, and mitigation and adaptation.
Sources & how we know this
- OCR GCSE (9-1) Geography B (J384) specification — OCR (2016)