A biology teacher asks students to give examples of genetic variations that support the idea that changes in a population’s environment affect genetic variation. Which is the least supportive example?
A. changes in genetics in human populations
B. antibiotic resistance in bacteria populations
C. pesticide resistance in garden insects
D. changes in the color of the peppered moth population in England
The correct answer and explanation is:
The least supportive example is A. changes in genetics in human populations.
Genetic variation in human populations can result from a variety of factors, including mutations, genetic drift, and gene flow, but human populations generally experience changes in their environment over much longer periods. While there may be some immediate responses to environmental changes (like skin color variations due to sunlight exposure), most human genetic adaptations occur on a much slower time scale compared to bacteria or insects. The examples of antibiotic and pesticide resistance, as well as the changes in the peppered moth population, directly illustrate the immediate impact of environmental changes on genetic variation in relatively short time spans.
B. Antibiotic resistance in bacteria populations is a clear example of how environmental factors (such as the use of antibiotics) can rapidly influence genetic variation. Bacteria that are exposed to antibiotics undergo mutations that allow them to survive, leading to a population of antibiotic-resistant bacteria. This change happens over just a few generations.
C. Pesticide resistance in garden insects works in a similar way. Insects exposed to pesticides undergo selective pressure, and over generations, those with genetic variations that confer resistance to the pesticide survive and reproduce, making the resistance trait more common in the population.
D. Changes in the color of the peppered moth population in England is a famous example of how environmental changes, specifically the industrial revolution, influenced genetic variation. Pollution from factories darkened tree bark, and darker moths had a survival advantage because they were better camouflaged from predators. Over time, the frequency of dark-colored moths increased in polluted areas.
In contrast to these examples, changes in human genetics typically do not reflect rapid adaptations to environmental changes within a single generation or even a few generations. Genetic changes in humans occur at a slower pace due to longer life cycles, smaller reproductive rates, and social factors that often buffer direct environmental pressures.