Problem 5 - Campbell Biology Concepts & Connections

Question

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 \(\quad\) (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.

Step-by-Step Solution

Answer

b. preserve genetic variation in the grass population.

Step 1: Understand the Situation

The biologist observed that grass plants with different types of leaves (curled and flat) have different reproductive success depending on whether the year is dry or wet. This suggests that the success of certain traits fluctuates based on environmental conditions.

Step 2: Identify Environment-Dependent Traits

Curled leaves are advantageous in dry years, while flat leaves are advantageous in wet years. This implies that no single trait is universally favoured.

Step 3: Evaluate Genetic Variation

Since both traits (alleles for curled and flat leaves) offer reproductive advantages depending on the environmental condition, there is a reason for both traits to be maintained in the population.

Step 4: Determine the Outcome

In this fluctuating environment, genetic variation is beneficial as it allows the population to thrive under varying conditions. Therefore, the presence of both alleles will be preserved due to their respective advantages in different circumstances.

Step 5: Select the Best Answer

The description suggests that genetic variation will be preserved in the grass population because different traits are advantageous in different environmental conditions.

Key Concepts

Alleles

Alleles are different versions of the same gene that are found at the same location on a chromosome. They are responsible for the variations in traits that we see within a population. In plants, alleles can determine characteristics such as leaf shape, flower color, or drought tolerance.
In the context of the exercise, grass plants have alleles for either curled or flat leaves. These alleles help the plants adapt to varying environmental conditions. In dry years, alleles for curled leaves provide a reproductive advantage, whereas in wet years, alleles for flat leaves become more beneficial. This variation ensures that the population can survive different climate conditions. By maintaining multiple alleles in the population, plants increase their chances of thriving, no matter the weather conditions.

Environmental Adaptation

Environmental adaptation refers to the process by which organisms adjust to changes in their environment. This is crucial for their survival and reproductive success.
In the exercise, the grass plants exhibit environmental adaptation by having different leaf shapes that are suited to dry or wet conditions. Curled leaves help the grass conserve water during dry periods, while flat leaves are advantageous when water is abundant. Environmental adaptation ensures that at least some individuals in the population will have favorable traits to survive and reproduce under varying environmental conditions.

• In dry years, curled-leaf plants have a survival advantage.
• In wet years, flat-leaf plants reproduce more successfully.

This continuous shifting ensures that the population as a whole remains robust and can withstand various climate scenarios.

Reproductive Success

Reproductive success is a key factor in the persistence and evolution of species. It refers to the number of offspring an individual can produce and ensure reach reproductive age themselves.
In the grass population example, the varying leaf shapes (curled and flat) directly influence reproductive success based on environmental conditions. Plants with alleles for curled leaves are more likely to reproduce successfully during dry years because their leaf shape reduces water loss, making them more likely to survive long enough to reproduce.
Conversely, in wet years, plants with flat leaves can maximize their growth and reproductive output because they can efficiently process the abundant water. This balance between different traits helps maintain genetic diversity within the population and provides a buffer against environmental changes.
In conclusion, the right mix of genetic traits (alleles) and adaptability to the environment ensures the reproductive success of the plants, allowing their genes to be passed on to future generations.