![]() Extinctions can also empty ecological niches and make an adaptive radiation possible. On an island, however, these niches may be empty. On the mainland, other species may fill all the possible ecological niches, making it impossible for a lineage to split into new forms and diversify. ![]() Lineages that invade islands may give rise to adaptive radiations because the invaders are free from competition with other species. For example, beetle radiations may have been triggered by adaptations for feeding on flowering plants. A key adaptation may open up many new niches to an organism and provide the opportunity for an adaptive radiation. Photo © Windsor Aguirre The evolution of a key adaptationĪ key adaptation usually means an adaptation that allows the organism to evolve to exploit a new niche or resource. Beetle radiations may have been triggered by adaptations for feeding on flowering plants. Different factors may trigger adaptive radiations, but each is a response to an opportunity. Information on controversies in the public arena relating to evolutionĪn adaptive radiation generally means an event in which a lineage rapidly diversifies, with the newly formed lineages evolving different adaptations.Alignment with the Next Generation Science Standards.The big issues – Pacing, diversity, complexity, and trends.Macroevolution – Evolution above the species level.Microevolution – Evolution within a population.Mechanisms: the processes of evolution – Selection, mutation, migration, and more.The history of life: looking at the patterns – Change over time and shared ancestors.An introduction to evolution: what is evolution and how does it work?.Examples of small-scale adaptive radiation associated with the formation of geographical races are found in the cases of the Kamchatka great spotted woodpecker ( Dendrocopus major Kamtschaticus ) and the Talysh lesser spotted woodpecker ( Dendrocopus minor quadrifasciatus ) or in races of the ordinary spruce-Norway ( Picea excelsa), Siberian ( Picea obovata), and Finnish ( Picea fennica). Large-scale adaptive radiation is found in the evolution of amphibians, some aquatic forms of which have tails (Urodela), while strictly amphibious forms preserve the tail only in the larval stage (Anura), and a third group, the dry-land forms, have lost their legs and assumed a serpentine character (Apoda). The scale of adaptive radiation may differ from one case to another. The main origin of adaptive radiation is found in intraspecies processes such as genetic diversity of species populations, differentiation of the species into geographical and ecological races as a result of enlargement of the territory under favorable conditions, and intraspecies contradictions. Darwin, who employed the term “divergence.” Adaptive radiation is fundamental to all forms of adaptogenesis and is the result of the acquisition by organisms of special accommodations-adaptations and penetrations into new adaptive zones. Osborn in 1915, although the idea had already been advanced by C. The term was proposed by the American scientist H. The formation of diverse organismic forms within the limits of a species or a group of related species.
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