Adaptive radiation: The growth of a variety of species from the single ancestral form; occurs when a new habitat becomes accessible to a population. The evolutionary pattern of divergence of a great many taxa from the common ancestral species as a result of the novel adaptations or a recent mass extinction. Examples of this are: the mammals during the Cenozoic Era after extinction of dinosaurs at the close of the Mesozoic Era flowering plants during the Cretaceous Period diversified because of their reproductive advantages over gymnosperm and non-seed plants which dominated the floras of the world at that time.