Which type of species has a significant impact on its ecosystem due to its role?

The choice of keystone species as the correct answer highlights the critical role certain species play within their ecosystems, where they have a disproportionately large impact relative to their abundance or biomass. Keystone species contribute to the structure, diversity, and functioning of an ecosystem. Their activities help maintain the balance of the ecosystem, supporting a wide range of other organisms and ecological processes.

For instance, a predator that regulates the population of herbivores can prevent overgrazing, allowing vegetation to flourish, which in turn supports various other species that rely on that vegetation for habitat and food. The removal of a keystone species can lead to dramatic changes in the ecosystem, often resulting in ecological collapse or a significant shift in species composition and abundance.

In contrast, while invasive species can also have a large impact on ecosystems, their effects are typically negative, often disrupting existing ecological balances and threatening native species. Endangered and threatened species are terms that describe the conservation status of certain species at risk of extinction but do not inherently reflect their ecological role or impact on ecosystem dynamics. Thus, while they may be important to conservation efforts, they do not necessarily have the same level of ecosystem influence as keystone species.