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. Understand the concept of genetic variation: Genetic variation refers to the diversity in gene frequencies within a population. Populations with higher genetic variation have a greater potential for adaptation to environmental changes, such as heat tolerance.
2. Analyze the two strains: The wild strain of Drosophila melanogaster is likely to have higher genetic variation because it has been exposed to natural environmental pressures, which promote diverse genetic traits. In contrast, the laboratory strain may have undergone controlled breeding, reducing genetic diversity.
3. Consider the role of selection pressure: Selection pressure, such as heat tolerance, acts on existing genetic variation. A population with greater genetic variation will have more individuals with traits that can be selected for heat tolerance, leading to a faster and more extensive response.
4. Evaluate the expected response: The wild strain is expected to show a more rapid and extensive response to heat-tolerance selection due to its higher genetic variation. The laboratory strain may respond more slowly or less extensively because of reduced genetic diversity.
5. Summarize the reasoning: The wild strain's exposure to natural environments likely resulted in greater genetic diversity, making it better equipped to adapt to heat-tolerance selection compared to the laboratory strain, which may have been subject to genetic bottlenecks or reduced variation.

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 Drosophila strains, the wild strain may have already undergone natural selection for heat tolerance, potentially leading to a more rapid response to selection pressures compared to the laboratory strain, which may have been bred under controlled conditions.

Genetic Variation

Genetic variation refers to the diversity in gene frequencies within a population. It is crucial for evolution and adaptation, as it provides the raw material for natural selection. The wild strain of Drosophila may exhibit greater genetic variation due to its exposure to diverse environmental pressures, which could enhance its ability to adapt to heat tolerance more quickly than the more homogenous laboratory strain.

Phenotypic Plasticity

Phenotypic plasticity is the ability of an organism to change its phenotype in response to environmental conditions. This concept is important in understanding how Drosophila can adapt to heat stress. The wild strain may possess greater phenotypic plasticity, allowing it to exhibit a range of responses to heat that could facilitate a more rapid adaptation compared to the laboratory strain, which may have a more fixed phenotype due to selective breeding.