A keystone species is one that has a large impact on its community. They have an important role in the ecosystem’s function and without them there would be very significant changes in the ecosystem. A keystone species is different than a dominant species, as a dominant species is more abundant, while a keystone species if very impactful but less abundant. They alter their habitat and affect many other species.
An otter is an example of a keystone species. (http://www.eoearth.org/view/article/51cbee487896bb431f696afe/)
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