Edexcel IGCSE Biology · Section 4
Ecology & the Environment
Energy and nutrients flowing through ecosystems, the carbon and nitrogen cycles, and the human impact on the environment.
What this section covers
Ecology is about interactions between organisms and their environment. Students need to interpret food chains and pyramids, understand nutrient cycles, and explain how human activity affects ecosystems.
- Use ecology key terms correctly, including population, community and ecosystem.
- Describe feeding relationships and energy transfer.
- Explain the carbon cycle and nitrogen cycle.
- Evaluate the effects of pollution, global warming and deforestation.
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1
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Ecology Key Terms
Spec 4.1
Key ecology terms you need to know — population, community, habitat and ecosystem.
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2
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Comparing Habitats and Biodiversity with Quadrats
Spec 4.2, 4.4B
Covers compare populations in two areas using quadrats, Measure abundance, frequency and percentage cover and Use quadrat data to compare biodiversity.
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3
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Studying Ecosystems
Spec 4.2-4.5
How to study ecosystems using quadrats and transects to estimate the size of populations.
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4
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Feeding Relationships
Spec 4.6-4.9
Food chains and food webs, energy transfer between levels, and pyramids of number and biomass.
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5
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The Carbon Cycle
Spec 4.10
How carbon moves through the environment via photosynthesis, respiration, decay and combustion.
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6
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The Nitrogen Cycle
Spec 4.11B
The nitrogen cycle and the roles of the different types of bacteria within it.
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7
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Air Pollution and Global Warming
Spec 4.12-4.15
The causes and effects of air pollution, acid rain, and the greenhouse effect and global warming.
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8
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Human Sources of Greenhouse Gases
Spec 4.14
Covers match named greenhouse gases to human sources, Explain how they increase the greenhouse effect and Suggest source-specific ways to reduce emissions.
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9
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Water Pollution and Deforestation
Spec 4.16-4.18B
How eutrophication pollutes water, and the environmental impact of deforestation.
Frequently asked questions
What is the difference between a population and a community?
A population is all the organisms of one species in a habitat; a community is all the populations of different species living together.
How do you use a quadrat to estimate population size?
Place quadrats randomly, count the organisms inside each, find the mean, then scale up to the total area of the habitat.
What is the carbon cycle?
The movement of carbon through the environment by photosynthesis, respiration, decomposition and combustion.
What causes global warming?
Rising levels of greenhouse gases such as carbon dioxide and methane trap more heat in the atmosphere, raising global temperatures.
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