Predation is when one organism, the predator, kills and eats another, the prey. The sizes of predator and prey populations are linked, and often rise and fall in regular cycles.
1. The prey population increases, so there is more food for predators.
2. More predators survive and breed, so the predator population increases.
3. More prey are eaten, so the prey population decreases.
4. Now there is less food for the predators, so fewer survive and breed, and the predator population decreases.
5. With fewer predators, fewer prey are eaten, so the prey population increases again, and the cycle repeats.Two features of the graph are important:
• the predator peaks come after the prey peaks (there is a time lag), because it takes time for more food to become more predator offspring;
• the predator population is usually smaller than the prey population, because energy is lost at each trophic level.A famous example is the snowshoe hare and the lynx in Canada, whose numbers cycle about every 10 years. However, predation is rarely the only cause. The hare population is also affected by its own food supply and by disease, and other factors such as weather affect both species. Real cycles are therefore less regular than simple laboratory models.Predation is also a selection pressure: the prey that are slowest or least well camouflaged are most likely to be eaten.
1. The prey population increases, so there is more food for predators.
2. More predators survive and breed, so the predator population increases.
3. More prey are eaten, so the prey population decreases.
4. Now there is less food for the predators, so fewer survive and breed, and the predator population decreases.
5. With fewer predators, fewer prey are eaten, so the prey population increases again, and the cycle repeats.Two features of the graph are important:
• the predator peaks come after the prey peaks (there is a time lag), because it takes time for more food to become more predator offspring;
• the predator population is usually smaller than the prey population, because energy is lost at each trophic level.A famous example is the snowshoe hare and the lynx in Canada, whose numbers cycle about every 10 years. However, predation is rarely the only cause. The hare population is also affected by its own food supply and by disease, and other factors such as weather affect both species. Real cycles are therefore less regular than simple laboratory models.Predation is also a selection pressure: the prey that are slowest or least well camouflaged are most likely to be eaten.