Predation
Laura Armstrong & Joe Wolfensohn
Teachers
Recall Questions
This topic requires prior knowledge of predator and prey relationships from GCSE Biology. You can test your knowledge on these below.
What is a predator?
An organism that hunts, kills, and eats other organisms.
What is a prey species?
An organism that is hunted and eaten by a predator.
How do predator populations affect prey populations?
Predator populations, when increased, can reduce prey numbers, affecting the food chain and ecosystem balance.
Topic Explainer Video
Check out this @JoeDoesBiology video that explains predation or read the full notes below. Once you've gone through the whole note, try out the practice questions!
What Is Predation?
Predation is a biological interaction where one organism (the predator) captures and feeds on another organism (the prey). It is a biotic factor that directly influences population sizes, species distribution, and natural selection.
The Predator–Prey Cycle
Predation leads to cyclical fluctuations in both predator and prey population sizes. This is best described using a predator–prey graph.
How the cycle works:
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Prey population increases – There is more food available for predators.
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Predator population increases – More food allows predators to survive and reproduce, increasing in numbers.
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Prey population decreases – Predators overhunt the prey, reducing their numbers.
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Predator population decreases – Less food causes predator numbers to fall as animals starve and die.
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Prey population increases again – With fewer predators, prey reproduce successfully.
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The cycle repeats.
Example: Lynx and Snowshoe Hare
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Prey: Snowshoe hare
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Predator: Canadian lynx
Records show a cyclical rise and fall in both populations over ~10-year periods, demonstrating the predator–prey dynamic.
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Ecological Implications
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Natural Selection: Prey species evolve adaptations like camouflage, speed, or warning coloration.
- Predators also evolve to become better hunters (e.g. sharper teeth, sharp claws and keen vision).
Key Terms
- Predation: An interaction where one organism kills and eats another.
- Predator: An organism that hunts and kills other organisms for food.
- Prey: An organism that is eaten by a predator.
- Predator–Prey Cycle: A repeating pattern of population changes caused byinteractions between predator and prey.
- Biotic Factor: A living factor that influences population size, such as predation.
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Exam Tips
When interpreting a predator–prey graph:
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Always describe both populations.
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Use time lags between peaks and troughs to explain causation, e.g., prey increases before predator increases. This is because reproduction of the predator population takes time before the increase in numbers is seen.
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Don’t assume population change is only due to predation – consider other abiotic and biotic factors that may affect population sizes.
No answer provided.
Impala and wildebeest are species of herbivore that live in large groups. They spend most of their time feeding with their heads down.
Scientists investigated the relationship between the number of predators in an area and the mean proportion of time these herbivores spent with their heads up, looking around rather than feeding. They obtained data from groups of impala and wildebeest in two areas. In one area there were few predators and in the other area there were many predators.
The graph shows their results. The bars show standard deviations.
Supporting statements:
1. Both species mean time spent looking around greater where many predators.
2. Differences (appear to be) significant because SDs do not overlap.
Statements that do not support:
3. Wildebeest spend similar mean time looking around where many predators as impalas where few predators.
4. Don’t know what they are looking for when their heads are up.
5. Habitats might be different in different areas which could affect their behaviour.
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!