A Level Biology Practice Exam

What is the role of keystone species in an ecosystem?

1. To decrease the population of other species

2. To maintain biodiversity with a large effect relative to their abundance

3. To primarily serve as prey for many organisms

4. To act as predators for every other species

The correct answer is: To maintain biodiversity with a large effect relative to their abundance

The correct response highlights that keystone species play a critical role in maintaining the structure and diversity of an ecosystem, often having a disproportionate impact relative to their abundance. These species contribute to the ecological balance by influencing the population sizes and distribution of other species within the ecosystem. Their presence helps to maintain species diversity, ensuring that ecosystems remain resilient and functional. For example, a keystone predator can control the population of prey species, which in turn supports the growth of plant communities and the overall health of the ecosystem. By keeping dominant species in check, keystone species prevent any one species from monopolizing resources, thereby fostering a diverse range of organisms to coexist. This intricate balance underscores the importance of keystone species in promoting biodiversity and ecological stability.