Darwin finches


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  • When Charles Darwin first saw the Galapagos Islands he described them as 10 islands “situated under the equator.” He noted that they originated as volcanoes and were pockmarked with craters. “Some of the craters, surmounting the larger islands, are of immense size, and they rise to a height of between three and four thousand feet.”
  • Noting differences in the feeding habits of the finches, Darwin wrote that cactus finches “may often be seen climbing about the flowers of the great cactus trees.” Seeing the diversity of beaks and other structures in the closely related finches, he wrote in his notebook, “one might really fancy that one species had been taken and modified for different ends.”
  • Darwin elaborated on this idea when he published his intellectual bombshell, the “Origin of Species,” some 25 years later in 1859. He speculated that birds, resembling starlings, came to the Galapagos Islands by wind. Evolution took over and different groups developed different diets. When, he wrote, “an immigrant first settled on one of the islands, … it would undoubtedly be exposed to different conditions in the different islands (where) it would have to compete with a different set of organisms. … Then, natural selection would probably favor different varieties in the different islands.”
  • In other words, beaks changed as the birds developed different tastes for fruits, seeds, or insects picked from the ground or cacti. Long, pointed beaks made some of them more fit for picking seeds out of cactus fruits. Shorter, stouter beaks served best for eating seeds found on the ground. Eventually, the immigrants evolved into 14 separate species, each with its own song, food preferences, and beak shapes. Warbler finches, for example, catch insects in beaks that are sharper and more slender than those of cactus eaters.
  • Asked about the possibility of calmodulin in the heads of humans, Abzhanov answers, “At this point we don’t know whether mammals in general or humans in particular employ calmodulin during development of their skulls and faces. It is, however, very likely as calmodulin appears to be involved in very basic craniofacial developmental processes. We do know it is expressed at the right time and in the right place in the development of mice embryos. We will certainly pursue its role(s) during both mouse and chicken development.”
  • Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in heritable traits of a population over time.
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