Pearson Edexcel International GCSE Biology · specification 4BI1 · Paper 1 | Whole paper: Core content, all five topics · Free · no account needed
4(c) Cycles within ecosystems (4BI1 specification)
How carbon and nitrogen move between organisms and the environment, and never run out.
Learn it on Incandio
The 2 Incandio pages that teach this — each explained in full, then proved in marked questions, taught back to an AI pupil and defended in a debate. Completely free.
- 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.
- The Carbon and Nitrogen Cycles — The same atoms, used again and again — and the four bacteria that do the work nothing else can.
The teaching route this belongs to: Topic 4 · Ecology and the environment (Biology) — the lessons in order, with every gate.
Specification coverage
Topic 4 Ecology and the environment (c) Cycles within ecosystems — statements 4.9–4.10
Assessment objectives: AO1, AO2. Suggested learning time: 50 minutes.
Required knowledge
- The carbon cycle, including photosynthesis, respiration, decomposition and combustion
- The nitrogen cycle, including the roles of nitrogen-fixing, nitrifying, denitrifying and decomposing bacteria
Required skills
- Name the process occurring at each arrow of a cycle diagram
- Explain the role of a named group of bacteria
How it is examined
- Multiple-choice and short-answer recall
- Application of the content to an unfamiliar context
- Extended open-response, marked on the quality of a connected explanation
Common mistakes
- Naming the bacteria without saying what each converts into what. The conversion is the mark.
- Forgetting decomposition, which appears in both cycles and is frequently omitted.
This page maps the specification. The pages above teach it, and the Biology lessons hold the whole course — completely free.