What's covered
Key facts
Decomposers (bacteria and fungi) break down dead organisms and waste, recycling nutrients back into the soil.
An ecosystem is all the living organisms in an area plus their non-living environment, and the interactions between them.
Only about 10% of the energy at one trophic level is transferred to the next; most is lost as heat through respiration or in undigested waste.
In a food chain, an arrow shows the direction energy flows — it points from the organism being eaten to the organism doing the eating.
A food web shows the feeding relationships between many species in an ecosystem; it is made up of many overlapping food chains.
A habitat is the place where an organism lives, providing the conditions and resources it needs to survive.
A herbivore is an animal that eats only plants; a carnivore is an animal that eats only other animals (meat); an omnivore eats both.
Producers are organisms (plants, algae) that make their own food through photosynthesis; they are the start of every food chain.
A quadrat is a square frame placed on the ground to sample and count the plants or slow-moving animals in a fixed area, allowing populations to be estimated.
Sample questions
A taste of the 10 questions in this topic, answers marked. Sign up to practise the full set with spaced repetition.
What is an ecosystem?
- •A single species in a habitat area
- ✓Community of organisms with their environment
- •Only the predator-prey pairs in habitat
- •Only the producers in a local area
What does an arrow in a food chain show?
- ✓Direction energy flows
- •Predator pointing at prey
- •Reproduction direction
- •Who lives where
Why does energy decrease up a food chain?
- •Energy is destroyed in cells
- ✓Lost as heat, waste, and movement
- •Predators are smaller than prey
- •Producers store all their energy
What is a habitat?
- •The group of all herbivores
- ✓The place where an organism lives
- •The smallest unit of life
- •The total energy in the food chain
Which sampling method counts plants in a fixed area?
- •Insect pooter
- •Pitfall trap
- ✓Quadrat sampling
- •Sweep net catch
Removing one species from a food web keeps every other population exactly the same size.
Answer: False
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