Ecology Practice Exam 2026 – Comprehensive Prep for Certification

A keystone species is characterized by its disproportionately large effect on its environment relative to its abundance. This means that even though it may not be the most numerous species in a given ecosystem, its presence and activities are crucial for maintaining the structure and health of that ecosystem. For instance, the removal of a keystone species can lead to significant changes in the ecosystem, potentially causing a decline in species diversity or leading to the dominance of less beneficial species.

An example of a keystone species is the sea otter, which helps control sea urchin populations. If sea otters are removed from the ecosystem, sea urchin populations can explode, leading to overgrazing of kelp forests and significant habitat degradation. This underscores the idea that keystone species play a critical role in their ecological communities, ensuring the balance and sustainability of the environment.