Ecosystems and interdependence · Grade 11
In Grade 11 you learn: predator and prey cycles.
An ecosystem is all the living things in an area together with their non-living surroundings: a pond, a wood, a coral reef. The organisms depend on each other for food, shelter and pollination, and they compete for what they need. Living and non-living factors decide which organisms can survive there and how many.
Key facts
- Predator and prey numbers rise and fall in cycles. When prey increase, predators have more food and increase too, a little later; then prey decrease, and later so do predators.
- A stable community keeps roughly the same species and numbers over time, because its biotic and abiotic factors stay in balance (for example a tropical rainforest).
Worked examples
Example 1
The graph shows the numbers of hares (prey) and lynx (predators) over many years. Explain the pattern.
Answer: more hares means more food for lynx, so lynx increase; then more hares are eaten, so hares fall; with less food, lynx fall; then hares recover