Students in a genetics laboratory began an experiment in an attempt to increase heat tolerance in two strains of Drosophila melanogaster. One strain was trapped from the wild six weeks before the experiment was to begin; the other was obtained from a Drosophila repository at a university laboratory. In which strain would you expect to see the most rapid and extensive response to heat-tolerance selection, and why?

Verified step by step guidance

1. <span>Identify the two strains of <em>Drosophila melanogaster</em>: one from the wild and one from a laboratory repository.</span>
2. <span>Consider the genetic diversity of each strain. Wild populations typically have higher genetic diversity compared to laboratory strains, which may have been inbred or selected for specific traits over generations.</span>
3. <span>Understand that higher genetic diversity in a population can lead to a more rapid and extensive response to selection pressures, such as increased heat tolerance, because there is a greater pool of genetic variations that might confer the desired trait.</span>
4. <span>Predict that the wild strain is likely to show a more rapid and extensive response to heat-tolerance selection due to its higher genetic diversity, providing more opportunities for beneficial mutations to be present and selected for.</span>
5. <span>Conclude that the laboratory strain may have a slower or less extensive response due to potentially reduced genetic diversity, limiting the available genetic variations that could be selected for increased heat tolerance.</span>

Key Concepts

Natural Selection

Natural selection is a fundamental mechanism of evolution where organisms better adapted to their environment tend to survive and produce more offspring. In the context of the experiment, the wild strain of Drosophila may have already undergone adaptations to local environmental conditions, including heat tolerance, making them potentially more responsive to selection pressures.

Genetic Variation

Genetic variation refers to the diversity in gene frequencies among individuals within a population. This variation is crucial for evolution, as it provides the raw material for natural selection. The wild strain may exhibit greater genetic diversity due to its exposure to varying environmental conditions, which could enhance its ability to adapt to heat tolerance compared to the laboratory strain.

Laboratory vs. Wild Strains

Laboratory strains of organisms, such as Drosophila, are often bred under controlled conditions and may lack the genetic diversity and adaptive traits found in wild populations. This can limit their ability to respond to environmental changes, such as increased temperatures. In contrast, the wild strain is likely to have evolved traits that confer survival advantages in fluctuating environments, making it more likely to show rapid adaptation to heat tolerance.