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Zorluk: ZorEvolution and Adaptation

A botanical study monitors a population of desert shrubs over several decades during an extended regional drought. At the start of the study, the population showed variation in leaf cuticle thickness. By the end of the drought period, the average cuticle thickness across the entire population had significantly increased. Which of the following best explains how this evolutionary change occurred?

  1. A
    Individual shrubs actively thickened their leaf cuticles during their lifespan to reduce water loss, passing this newly developed trait to their seeds.
  2. Shrubs with pre-existing heritable variations for thicker cuticles had higher survival and reproductive rates, increasing the frequency of those alleles in subsequent generations.Cevap
  3. C
    The allele responsible for a thick cuticle is dominant, meaning it naturally became the most common phenotype in the population regardless of survival advantages.
  4. D
    Severe drought stress caused individual plants to deliberately mutate their cellular DNA during the dry seasons to prevent dehydration.

Cevap

Shrubs with pre-existing heritable variations for thicker cuticles had higher survival and reproductive rates, increasing the frequency of those alleles in subsequent generations.
Natural selection operates on pre-existing genetic variation within a population. Shrubs that possessed alleles for thicker cuticles were better equipped to conserve water during the prolonged drought, resulting in higher survival and reproductive success. Over successive generations, these advantageous alleles became more frequent in the gene pool, increasing the average cuticle thickness across the population.

Adım Adım Çözüm

1
Identify the biological mechanism driving population-wide trait shifts.
Evolution by natural selection requires pre-existing genetic variation, differential survival/reproduction, and heritability.
Populations evolve over generations when selective pressures favor individuals possessing advantageous heritable traits.
2
Evaluate the environmental selective pressure described in the scenario.
Prolonged drought creates a selective advantage for plants that lose less water through their leaves.
Plants possessing thicker cuticles conserve more water, making them more likely to survive severe drought conditions.
3
Trace the transmission of advantageous alleles across generations.
Surviving plants reproduce and pass the alleles for thicker cuticles to their offspring, shifting the population mean.
Natural selection changes allele frequencies at the population level rather than modifying the genetic makeup of individual organisms during their lifetime.

Anahtar Kavram

Natural Selection and Population Adaptation
Tahmini Süre:1m 30s
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Evolution and Adaptation

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