Answer :
Final answer:
A keystone species plays a critical role in an ecosystem by maintaining biodiversity and community structure. The removal of a keystone species can lead to significant changes, often resulting in decreased biodiversity and altered species composition. Examples include the intertidal sea star and the banded tetra, both of which have large impacts on their ecosystems.
Explanation:
Main Role of a Keystone Species
A keystone species is one whose presence is key to maintaining biodiversity within an ecosystem and to upholding an ecological community's structure. The intertidal sea star, Pisaster ochraceus, found in the northwestern United States, serves as a classic example of a keystone species. Studies have shown that when this organism is removed from its habitat, populations of its natural prey (such as mussels) increase dramatically. This increase leads to a decrease in algal diversity, completely altering species composition and reducing overall biodiversity.
Another example of a keystone species is the banded tetra, a fish in tropical streams. This species contributes nearly all of the phosphorus necessary for plant growth in the ecosystem. If key species like the banded tetra or the sea star were to become extinct, the community could face significant ecological imbalances and decreased ecosystem health.
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