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In population genetics, directional selection is a type of natural selection in which one extreme phenotype is favored over both the other extreme and moderate phenotypes. This genetic selection causes the allele frequency to shift toward the chosen extreme over time as allele ratios change from generation to generation.
The McDonald–Kreitman test [1] is a statistical test often used by evolutionary and population biologists to detect and measure the amount of adaptive evolution within a species by determining whether adaptive evolution has occurred, and the proportion of substitutions that resulted from positive selection (also known as directional selection).
Directional selection appears to act on organisms' size, whereas it exhibits a far smaller effect on other morphological traits, [10] though it is possible that this perception may be a result of sample bias. [3] This selectional pressure can be explained by a number of advantages, both in terms of mating success and survival rate. [10]
The peacock tail in flight, the classic example of an ornament assumed to be a Fisherian runaway. Fisherian runaway or runaway selection is a sexual selection mechanism proposed by the mathematical biologist Ronald Fisher in the early 20th century, to account for the evolution of ostentatious male ornamentation by persistent, directional female choice.
The key quantity for genic capture is vaguely defined as "condition." The hypothesis only defines condition as a quantity that correlates tightly with overall fitness, such that directional selection will always increase average condition over time. Condition should, in general, reflect overall energy acquisition, such that life-history ...
Fiveable, an online learning community for high school students, made its first-ever acquisition earlier this week: Hours, a virtual study platform built by a 16-year-old. Fiveable is a free ...
In statistical hypothesis testing, the alternative hypothesis is one of the proposed propositions in the hypothesis test. In general the goal of hypothesis test is to demonstrate that in the given condition, there is sufficient evidence supporting the credibility of alternative hypothesis instead of the exclusive proposition in the test (null hypothesis). [1]
For a population undergoing directional selection, the main axis of variation (largest axis of the white ellipse) will bias the main direction of the trajectory toward the fitness optimum (arrow). The rate of morphological change will be inversely proportional to the angle (beta) formed between the direction of selection (dashed line) and the ...