Question

A geneticist mixed together many different kinds of fruit flies-some with long wings, some with short wings, some with red eyes, some with brown eyes, and so on. He allowed the flies to feed, mate randomly, and reproduce by the millions. After many generations, most of the flies in the population had medium wings and red eyes, and most of the extreme types had disappeared. This experiment appears to demonstrate:
(A) Stabilising selection.
(B) Geographic variation
(C) Diversifying selection
(D) Genetic drift

Answer 1

Hint: Natural selection is of various types such as stabilising selection, diversifying selection, disruptive selection. The selection in which all the extremes are wiped and the mean value is maximum in the population selection is known as stabilising selection.

Step by step solution:
Changes in heritable traits—an organism's hereditary characteristics—are the means through which organisms evolve. For instance, eye colour is a heritable trait in humans, and a person may get the "brown-eye trait" from one of their parents. Stabilizing Selection Stabilizing selection occurs when selective pressures choose between two extremes of a characteristic. For instance, stabilizing selection may have an impact on plant height. If a plant is too short, it might not be able to compete for sunlight with other plants. n stabilizing choice Extremes of the phenotypic are rejected in favour of the average phenotype. Moths at either extreme of colouration would be less successful in camouflaging and would be rejected in an area with fewer light-coloured lichen and fewer dark-coloured trees.
Geographical variation describes variations in genetically based features among populations over a species' natural geographic range. Population sizes (through genetic drift), patterns, distances, and rates of migration or dispersal and gene flow, as well as frequently natural selection—which is particularly noticeable where different geographic areas favour different phenotypes—determine the geographic patterns of genetic variation.
So, option (A) is correct.
Note: The geographic patterns of genetic variation are determined by population sizes (through genetic drift), patterns, distances, and rates of migration or dispersal and gene flow, as well as frequently natural selection—which is especially apparent where different geographic areas favour different phenotypes.