Communities are groups of different species found in the same place at the same time. The famous biologist Edward O. Wilson wrote, " In communities, there are little players and big players, and the biggest players are the keystone species. The removal of a keystone species causes a substantial part of the community to change drastically. An example of a keystone species is the California otter which almost became extinct due to hunting. When this happened, there was a population explosion of sea urchins which were the main food of otters. The urchins ate the kelp forests which were destroyed and the ocean floor became a desert.
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