Producers, consumers, trophic levels, predator–prey, food webs, ecological pyramids and why only about 10% of energy passes on.
6 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
If the hawk disappears from a forest, who wins and who loses? Follow the arrows.
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Copy these into your notebook in your own words — that is how they stick.
Organism that makes its own food by photosynthesis — green plants, algae, phytoplankton. Trophic level 1.
Primary (herbivores), secondary, tertiary (carnivores). Omnivores feed at more than one level.
Point from the food to the feeder = direction of energy flow.
Interconnected food chains; more stable because consumers have alternative foods.
Only ~10% passes on. Lost as heat from respiration, in movement, egestion (faeces), excretion and uneaten parts.
Too little energy remains after 4–5 transfers to support another population.
Numbers (can be inverted), biomass (mass of living material), energy (always upright).
The kind of support a teacher gives after the lesson: worked examples to attempt first, a board illustration, key terms, common misconceptions and memory aids.
Try it in your notebook first, then reveal the solution one step at a time.
Try it in your notebook first, then reveal the solution one step at a time.
| Pyramid of… | What each bar shows | Can it be upside down? |
|---|---|---|
| Numbers | Number of organisms at each level | Yes — one mango tree supports hundreds of insects |
| Biomass | Dry mass of living material at each level | Rarely — e.g. in the sea, where plankton reproduce fast |
| Energy | Energy flowing through each level (kJ m⁻² year⁻¹) | Never |
Only the pyramid of energy is always the right way up, because energy is lost at every level.
Read every arrow as “is eaten by”: grass is eaten by grasshopper. And the 10% rule: move up one level, move the decimal point one place left.
The invasive lionfish has spread across Caribbean reefs. It eats large numbers of small reef fish and has few local predators, so it disrupts reef food webs — which is why many islands encourage fishers to catch and eat lionfish.
List eight organisms you can see around your school. Draw a food web linking them, label each organism’s trophic level, and circle the producers.
3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness.
8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better.
Write full answers, then reveal the mark scheme and tick the points you earned (17 marks in total). Your answers are saved on this device.
Question 1 [9 marks]
A terrestrial food web: wild flowers and grass are eaten by rabbits and mice; the hawk eats rabbits and mice; the snake eats mice.
(a) Identify a producer, a predator and a primary consumer. [3]
(b) Explain why there are fewer organisms at the top of the food web than at the bottom. [2]
(c) Discuss TWO possible consequences of the hawk becoming extinct. [4]
Question 2 [8 marks]
Organisms and their foods: caterpillar, grasshopper, iguana and squirrel eat leaves, fruits and seeds; the great crested flycatcher eats grasshoppers and caterpillars; the hawk eats squirrels and iguanas.
(a) Identify TWO primary consumers. [2]
(b) Using all seven organisms, draw ONE food web (describe it in words if typing). [4]
(c) Identify ONE carnivore and state ONE role of the plant material. [2]
Find these in your own past-paper booklets for extra timed practice. The practice above is adapted from them.