In an area of erratic rainfall, a biologist found that grass plants with alleles for curled leaves reproduced better in dry years, and plants with alleles for flat leaves reproduced better in wet years. This situation would tend to _________ . (Explain your answer.)
a. Cause genetic drift in the grass population.
b. Preserve genetic variation in the grass population.
c. Lead to stabilizing selection in the grass population.
d. Lead to uniformity in the grass population.

Verified step by step guidance

1. Step 1: Begin by understanding the concept of genetic variation. Genetic variation refers to the diversity in gene frequencies within a population. It is essential for a population's ability to adapt to changing environmental conditions.
2. Step 2: Analyze the scenario described in the problem. The biologist observed that grass plants with curled leaves reproduce better in dry years, while plants with flat leaves reproduce better in wet years. This indicates that different environmental conditions favor different traits.
3. Step 3: Recognize the type of selection at play. This situation is an example of fluctuating selection, where environmental conditions change over time, favoring different traits in different years. This tends to maintain multiple alleles in the population.
4. Step 4: Evaluate the options provided in the question. Genetic drift (option a) refers to random changes in allele frequencies, which is not relevant here. Stabilizing selection (option c) reduces variation by favoring intermediate traits, which is also not applicable. Uniformity (option d) would imply a lack of variation, which contradicts the observed scenario.
5. Step 5: Conclude that the correct answer is option b, as fluctuating environmental conditions preserve genetic variation by maintaining both alleles for curled and flat leaves in the population.

Key Concepts

Natural Selection

Natural selection is a fundamental mechanism of evolution where individuals with traits better suited to their environment tend to survive and reproduce more successfully. In this scenario, grass plants with curled leaves thrive in dry conditions, while those with flat leaves excel in wet conditions, illustrating how environmental factors can influence which traits are favored over time.

Genetic Variation

Genetic variation refers to the diversity of alleles and genotypes within a population. In the context of the grass plants, the presence of both curled and flat leaf alleles allows for a range of adaptations to varying environmental conditions, which is crucial for the population's resilience and long-term survival.

Stabilizing Selection

Stabilizing selection is a type of natural selection that favors intermediate phenotypes and reduces variation in a trait. In this case, the alternating success of different leaf types in varying rainfall conditions suggests that rather than stabilizing selection, the population is experiencing a balancing selection, which maintains genetic diversity rather than leading to uniformity.