Answer :
Final answer:
The absence of a keystone species can have significant effects on the balance and structure of an ecosystem, leading to alterations in species composition and reduced biodiversity. Examples include the removal of intertidal sea stars and the extinction of banded tetra fish in tropical streams.
Explanation:
A keystone species is a species that is instrumental in maintaining diversity within an ecosystem. When a keystone species is absent from an ecosystem, it can have significant effects on the overall balance and structure of the ecosystem.
For example, the removal of the intertidal sea star species in the northwestern United States led to an increase in the population of their natural prey, mussels, which completely altered the species composition and reduced biodiversity.
In another example, the banded tetra fish in tropical streams supplies essential nutrients to the rest of the community. If these fish were to become extinct, it would greatly affect the entire community.
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