Question

decline or a keystone species can disrupt the delicate balance of the food web, and even lead to ecosystem - wide collapse. examples of keystone species include sea otters and alligators. which of the following organism is considered to be the most important organism in an ecosystem? keystone species realized species tertiary consumer

Explanation:

The text explicitly states that a keystone species is crucial as its decline can disrupt the food web and lead to ecosystem - wide collapse. This indicates its importance in an ecosystem. Realized species is not a term related to the most important organism in an ecosystem in this context. A tertiary consumer is just a trophic level and not necessarily the most important for the overall ecosystem balance as described for keystone species.

Answer:

keystone species