Question

Exit Ticket Scenario: Population Change & Ecosystem Impact
A group of rabbits lives in a grassland ecosystem where grass is their main food source. Over several years, the rabbit population increases rapidly due to mild winters and fewer predators. As the rabbit population grows, the grass population begins to decline. Eventually, the rabbits struggle to find enough food, and their population starts to decrease.

Constructed‑Response Prompt
Explain how a change in population size impacts an ecosystem.
Support your answer with evidence from the scenario.

Answer 1

A change in a population’s size alters how organisms use resources and interact, which can change the whole ecosystem. In the scenario, mild winters and fewer predators allow the rabbit population to grow quickly. Because rabbits eat grass, the larger rabbit population overconsumes the grass, so the grass population declines. With less food available, the rabbits cannot get enough energy to survive and reproduce, so their numbers fall. This sequence shows a density‑dependent feedback: when a population exceeds the ecosystem’s carrying capacity (the amount of resources available), resources become limiting and the population is forced back down. Such population swings can also ripple outward — for example, less grass can affect soil stability and other species that depend on the plants — until the system reaches a new balance.