A population of desert shrubs experiences an extended drought spanning several decades. Over successive generations, researchers observe that the average root depth in the population increases substantially. Which of the following best explains the mechanism behind this evolutionary change?
- AIndividual shrubs stretched their root systems deeper into the ground during the drought and passed those acquired root lengths to their offspring.
- Shrubs with pre-existing genetic variations for deeper roots had higher survival and reproductive success in arid conditions.Answer
- CThe deep-root trait is controlled by a dominant allele, causing it to automatically become the most frequent trait regardless of the environment.
- DEach shrub detected the lack of surface moisture and intentionally mutated its DNA to grow longer roots.
Answer
Shrubs with pre-existing genetic variations for deeper roots had higher survival and reproductive success in arid conditions.
Natural selection operates when environmental pressures favor individuals with specific pre-existing genetic traits. In this scenario, shrubs that already possessed alleles for deeper roots were better able to access deep soil moisture during the drought, leading to higher rates of survival and seed production.
Step-by-Step Solution
Key Concept
Natural selection drives population adaptation via differential reproductive success acting on existing genetic variation.
Estimated Time:1m 0s