This module covers how energy moves through living things and how biologists study who lives where. You will draw food chains with correct arrows, explain why energy is lost between feeding levels, interpret a change in a food web, estimate a population from a sample, and compare biomass with simple counts.
Check the current Cambridge IGCSE Biology 0610 syllabus for the exact content points in your exam year. The reasoning habits here stay useful across versions. Our Biology learning guide shows where ecology sits among the other modules.
What should you already know?
You should know that plants make food by photosynthesis and that animals get energy by feeding. It helps to have met respiration, because it explains where most of the lost energy goes: see gas exchange and respiration. You also need simple arithmetic: percentages, means and multiplying by an area.
An orienting example
A paddy field has this food chain: rice plant, grasshopper, frog, snake. Suppose the rice plants in one square metre capture 10 000 kJ of energy in a season (invented figure for practice), and the grasshoppers get 1 000 kJ of it.
Step 1, arrows: rice plant → grasshopper → frog → snake. Each arrow means “energy and nutrients pass to”.
Step 2, percentage passed on: 1 000 ÷ 10 000 × 100 = 10%.
Step 3, where is the rest? 10 000 − 1 000 = 9 000 kJ was not passed to grasshoppers. Some was never eaten, some was lost as heat from respiration by the plants, and some parts such as roots were not consumed.
One small example already uses three skills: arrow meaning, percentage efficiency and explaining a loss. The lessons below train each one separately.
In what order should you study the lessons?
- Construct a food chain with the correct arrow meaning: every other lesson depends on reading arrows correctly.
- Explain energy losses between trophic levels: this gives you the reasons and the percentage calculation.
- Interpret a food web change without claiming one inevitable outcome: this is where wording matters most.
- Calculate a sampling estimate with stated assumptions: the data-handling lesson, with quadrats and mark-recapture.
- Compare biomass and organism counts: it ties energy flow and sampling together.
Which traps catch students in this module?
- Drawing arrows from the eater to the food. The arrow points the way energy goes, from the food to the eater.
- Saying energy is “used up” or “destroyed”. Energy is transferred, and much of it leaves as heat.
- Writing that removing one species will definitely cause another to die out. A food web usually allows several outcomes.
- Forgetting the area of the quadrat or the area of the whole habitat when scaling up.
- Using organism counts when the question is about biomass.
How should you use the practice set?
Try the ecology and energy flow practice set after the lessons, and give the reason, not just the observation, in every explanation. Log each slip in a mistake log so the same error does not return. For food chains and webs, the food-web and energy-flow explorer lets you check arrow meaning and see several plausible effects of a change.
If you want a teacher to go through your own written answers, our online one-to-one Biology tuition is built around exactly that kind of work.