Figure 3.7. Studies of Natural Selection After Darwin. Stabilizing selection, directional selection, diversifying selection, frequency -dependent selection, and sexual selection all contribute to the way natural selection can affect variation within a population. This does not skew the bell curve in any way. a. Thus, the trade‐off between transmission rate and infection duration is expected to lead to stabilizing selection on pathogen virulence. Hawaiian honeycreepers, which are found only in Hawaii, have been found to have DNA commonalities with this group of finches that indicate they have a common ancestor. Each of the three modern finches has a beak adapted to its life history and diet. Disruptive selection. What kind of selection has acted on these finches? Stabilizing Selection. In stabilizing selection, the median phenotype is the one selected for during natural selection. Adaptive evolution in finches: Through natural selection, a population of finches evolved into three separate species by adapting to several difference selection pressures. These finches have experienced disruptive selection. 2 In 1973, Peter and Rosemary Grant—a husband and wife research team—went to the Galapagos Islands to find out exactly how finches showed Darwinian changes. While there is growing support for the assumption that virulence and ... Finches that had hatched in spring 2015 were retained, weighed, and banded with a numbered metal tag for individual identification. stabilizing selection. E) selection was acting more directly upon genotype than upon phenotype. speciation. For example, plant height might be acted on by stabilizing selection. ... stabilizing selection was occurring in these species concerning larynx size. Stabilizing selection tends to reduce the amount of variation in the phenotype distribution over an episode of selection. Problem : A population of arboreal rodents lives in one species of pine tree. Stabilizing selection When selective pressures select against the two extremes of a trait, the population experiences stabilizing selection. d. Peter and Rosemary Grant and their colleagues have studied Galápagos finch populations every year since 1976 and have provided important demonstrations of the operation of natural selection. Conditions will favor intermediate weight babies and so will result in stabilizing selection, c. A population of seed-cracker finches feeds on seeds available in two sizes, small or large Two populations will emerge if different beak types are best for the different sized seeds. Cardueline finches can be found in many areas of the world, including North America and Asia. For example, stabilizing selection is occurring if the finches with average-sized beaks are surviving and reproducing at higher rates than finches with very large or very small beaks. In the case of the Finches, the trait that is under selection is not a polygenic trait as in all of the previous examples. The most common of the types of natural selection is stabilizing selection. These pine trees have very evenly spaced branches of uniform thickness. Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true? The phenotype is also stabilized by selection. Demonstrations of evolution by natural selection can be time consuming. Stabilizing selection – a process of natural selection in which intermediate phenotypes are favored over phenotypes at the extremes. Azcolvin429 (Selection_Types_Chart.png) / GFDL. A) Each bird evolved a deeper, stronger beak as the drought persisted. The use of the Galapagos finches to represent Darwinian change came a century later through a landmark 1947 book called Darwin’s Finches. A plant that is too short may not be able to compete with other plants for sunlight. 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