Adaptive radiation is rapidly repeated speciation of the species of a particular evolutionary line. It has at least two different reasons. The first cause is the penetration of the representatives of a particular line into an environment that has many utilizable but, at the given time, unutilized resources. A species that enters such an environment in that, for example, it reaches an island, “learns” to utilize the individual resources and diversifies into a great many species through gradual adaptation to the individual types of resources and individual types of environment. The second cause of evolutionary radiation is the formation of fundamentally new features that, for some reason, open a broader range of so-far unused niches for their carriers. For example, the formation of wings and the ability to fly enables the particular group of vertebrates to utilize various types of resources with scattered occurrence over a large territory. As a consequence, thousands of species of birds could evolve relatively rapidly, using various types of resources as food, from seeds and fruit through insects, to vertebrates.
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