Radiación adaptativa: Diferenzas entre revisións
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Liña 31:
=== Innovación ===
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| title = Molar Tooth Diversity, Disparity, and Ecology in Cenozoic Ungulate Radiations
| journal = Science
Liña 41:
| pmid = 8929401
| doi = 10.1126/science.274.5292.1489
|bibcode = 1996Sci...274.1489J}}</ref>
| title = The Origin and Evolution of Birds
| first = Alan | last = Feduccia | year = 1999
}}</ref>
=== Oportunidade ===
As radiacións adaptativas adoitan ocorrer como resultado da orixe dun organismo nun ambiente con nichos non ocupados, como os lagos de nova formación ou unha cadea de illas. A poboación colonizada pode diversificarse rapidamente tomando vbantaxe de todos os nichos posibles.
Cando se formou o [[lago Vitoria]] como un lago illado no [[val do rift]] africano, unhas 300 especies de peixeds [[cíclidos]] radiaron adaptativaamente desdde unha especie parental e só 15.000 anos.
As radiacións adaptativas danse despois de [[extinción en masa|extincións en masa]]: despois dunha extinción, quedan vacantes moitos nichos. Un exemplo clásico disto é a substitución dos [[dinosauro]]s non aviarios polos mamíferos ao [[evento de extinción Cretáceo–Paleoxeno|final do Cretáceo]].
== Exemplos ==▼
▲== Exemplos ==
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=== Pimpíns de Darwin ===
One famous example where adaptive radiation is seen is with [[Darwin's finches]]. It has been observed by many evolutionary biologists that fragmented landscapes oftentimes are a prime location for adaptive radiation to occur. The differences in geography throughout disjointed landscapes such as islands are believed to promote such diversification. Darwin's finches occupy the fragmented landscape of the [[Galápagos Islands]] and are diversified into many different species which differ in ecology, song, and morphology, specifically the size and shapes of their [[beak]]s. The first obvious explanation for these differences is [[allopatric speciation]], speciation that occurs when populations of the same species become isolated geographically and evolve separately. Because the finches are divided amongst the islands, the birds have been evolving separately for several million years. However, this does not account for the fact that many of the species occur in [[sympatry]], with seven or more species inhabiting the same island.<ref name="Petren, K. 2005">{{cite journal | last1 = Petren | first1 = K. | last2 = Grant | first2 = P. R. | last3 = Grant | first3 = B. R. | last4 = Keller | first4 = L. F. | year = 2005 | title = Comparative landscape genetics and the adaptive radiation of Darwin's finches: the role of peripheral isolation | url = | journal = Molecular Ecology | volume = 14 | issue = 10| pages = 2943–2957 | doi=10.1111/j.1365-294x.2005.02632.x}}</ref> This raises the question as to why these species split when living in the same environment with all the same resources. Petren, Grant, Grant, and Keller proposed that the speciation of the finches occurred in two parts: an initial, easily observable allopatric event followed by a less clear sympatric event. This sympatric event which occurred second was adaptive radiation.<ref name="Petren, K. 2005"/> This occurred largely to promote specialization upon each island. One major morphological difference among species sharing one island is beak size and shape. Adaptive radiation led to the evolution of different beaks which could access different food and resources. Those with short beaks are better adapted to eating seeds on the ground, those with thin, sharp beaks eat insects, and those with long beaks use their beaks to probe for food inside cacti. With these specializations, seven or more species of finches are able to inhabit the same environments without competition or lack of resources killing several off. In other words, these morphological differences in beak size and shape brought about by adaptive radiation allow the island diversification to persist.
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