Pearson Edexcel International GCSE in Biology · 4BI1 · Free · no account needed
Topic 4 · Ecology and the environment
Organisms in their surroundings: populations, sampling with quadrats, food chains and pyramids, the carbon and nitrogen cycles, and the specific ways humans damage ecosystems.
Every lesson here ends the same way: learn it, teach it to an AI pupil who asks the awkward question, then defend it against the thinker with the strongest claim on it — free · no account needed.
8 lessons, covering 18 specification statements.
What you need to know — the 18 statements, and where each one is taught
Every statement this topic carries, in the specification's own numbering, with Incandio's restatement of what it asks and the lesson that discharges it. Tick them off against your own copy of the specification: this is the topic's revision checklist, not a summary of it. Incandio is aligned to this specification. It is not published by, endorsed by or affiliated with Pearson, and it reproduces none of Pearson's wording — the statement numbers are given so you can check every lesson against your own copy.
| Statement | What it asks | Taught in |
|---|---|---|
| 4.1 | The terms population, community, habitat and ecosystem | Populations, Ecosystems and Sampling with Quadrats |
| 4.2 (practical) | Practical: investigate population size in two areas using quadrats | Populations, Ecosystems and Sampling with Quadrats |
| 4.3 | The term biodiversity | Biodiversity, Distribution and Limiting Factors |
| 4.4 (practical) | Practical: investigate distribution and measure biodiversity using quadrats | Biodiversity, Distribution and Limiting Factors |
| 4.5 | How abiotic and biotic factors affect population size and distribution | Biodiversity, Distribution and Limiting Factors |
| 4.6 | Trophic levels: producers, primary, secondary and tertiary consumers, decomposers | Food Chains, Webs and Pyramids |
| 4.7 | Food chains, food webs, and pyramids of number, biomass and energy transfer | Food Chains, Webs and Pyramids |
| 4.8 | The transfer of substances and energy along a food chain | Energy Transfer Along a Food Chain |
| 4.9 | Why only about 10% of energy is transferred between trophic levels | Energy Transfer Along a Food Chain |
| 4.10 | The stages of the carbon cycle: respiration, photosynthesis, decomposition, combustion | The Carbon and Nitrogen Cycles |
| 4.11 | The stages of the nitrogen cycle and the roles of the bacteria involved | The Carbon and Nitrogen Cycles |
| 4.12 | Biological consequences of air pollution by sulfur dioxide and carbon monoxide | Air Pollution and the Greenhouse Gases |
| 4.13 | Water vapour, carbon dioxide, nitrous oxide, methane and CFCs as greenhouse gases | Air Pollution and the Greenhouse Gases |
| 4.14 | How human activities contribute to greenhouse gases | Air Pollution and the Greenhouse Gases |
| 4.15 | The enhanced greenhouse effect, global warming and its consequences | Global Warming and Deforestation |
| 4.18 | The effects of deforestation: leaching, soil erosion, evapotranspiration, the carbon cycle and atmospheric gases | Global Warming and Deforestation |
| 4.16 | Biological consequences of water pollution by sewage | Water Pollution and Eutrophication |
| 4.17 | Eutrophication caused by leached minerals from fertiliser | Water Pollution and Eutrophication |
The lessons
- Populations, Ecosystems and Sampling with Quadrats — Four nested words for where organisms live — and how to count a population you could never count in full. (4.1, 4.2)
- Biodiversity, Distribution and Limiting Factors — Why organisms are where they are and not somewhere else — and how to measure the variety of life in a place rather than just its quantity. (4.3, 4.4, 4.5)
- Food Chains, Webs and Pyramids — Who eats whom, drawn three different ways — and why only one of the three can come out upside down. (4.6, 4.7)
- Energy Transfer Along a Food Chain — About nine tenths of the energy disappears at every step. Here is exactly where it goes — and what that means for how the world is fed. (4.8, 4.9)
- The Carbon and Nitrogen Cycles — The same atoms, used again and again — and the four bacteria that do the work nothing else can. (4.10, 4.11)
- Air Pollution and the Greenhouse Gases — Two entirely different problems that both begin with burning — one that poisons what it touches, and one that changes the energy balance of the planet. (4.12, 4.13, 4.14)
- Global Warming and Deforestation — What a warmer planet does to living things — and why removing a forest changes the soil, the rainfall and the atmosphere all at once. (4.15, 4.18)
- Water Pollution and Eutrophication — Two things that should be harmless — treated sewage and plant fertiliser — and the same chain of events by which both empty a river of fish. (4.16, 4.17)