The term for a species that has a disproportionate effect on its ecosystem is keystone species. These species play critical roles in maintaining the structure, diversity, and health of their environment. Their presence or absence can lead to significant changes in ecosystem dynamics. Examples of keystone species include sea otters, which control sea urchin populations and maintain kelp forest ecosystems, and wolves, which regulate herbivore populations in terrestrial habitats. Protecting these species is vital for ecosystem conservation.