Biology

The correct answer is: A.A species that helps to hold an ecosystem together.

A keystone species is one that has a disproportionately large impact on its ecosystem relative to its abundance or biomass. It plays a critical role in maintaining the structure and balance of the ecosystem. For example, sea otters are considered keystone species because they help control sea urchin populations, which in turn allows kelp forests to thrive. Without the otters, urchin populations could explode, leading to the destruction of the kelp ecosystem.

Why the other options are incorrect:

B.Keys and stones have nothing to do with ecology: The term "keystone" comes from archite...