When one species evolves in response to changes in another species it is called coevolution. For example, when an adaptation evolves in a prey to reduce its chances of being eaten, the predator is under selection pressure to circumvent the new defense. This may result in a new adaptation in the predator. Species engaged in mutualistic interactions also show coevolution. The color of this flower pollinated by hummingbirds is red in response to the red color preference of hummingbirds. The elongation of the beak of the hummingbird and the elongation of the tube of the flower are the result of coevolution.

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