Directional, stabilizing and disruptive selection Knowledge-Based Download PDF

Questions

1. 1.

   How do stabilizing selection and directional selection differ in their effects on the mean phenotypic value and phenotypic variance of a continuous trait in a population?

   • A) Both types of selection shift the mean phenotype toward a higher value while expanding overall phenotypic variance.
   • B) Stabilizing selection shifts the mean phenotype toward an extreme, whereas directional selection maintains the mean at its initial value.
   • C) Stabilizing selection increases phenotypic variance by favoring both extremes, whereas directional selection leaves the variance unaffected.
   • D) Stabilizing selection reduces phenotypic variance while maintaining the mean, whereas directional selection shifts the mean phenotype toward one extreme.
2. 2.

   Which of the following biological examples illustrates disruptive selection?

   • A) Human infants with intermediate birth weights exhibit higher survival rates than those born unusually light or heavy.
   • B) Finches with either small or large beaks survive more successfully than intermediate-beaked individuals when only small and large seeds are available.
   • C) Peppered moths with darker wing pigmentation become predominant over light-colored individuals after industrial soot darkens tree trunks.
   • D) Giraffes with progressively longer necks survive more effectively by accessing foliage that shorter individuals cannot reach.
3. 3.

   Which mode of natural selection occurs when environmental changes favor individuals exhibiting a phenotype at one end of the trait distribution, causing the population mean for that trait to shift over time?

   • A) Directional selection
   • B) Stabilizing selection
   • C) Disruptive selection
   • D) Balancing selection
4. 4.

   Which mode of natural selection favors individuals at both phenotypic extremes over individuals with intermediate phenotypes, often resulting in a bimodal trait distribution?

   • A) Disruptive selection
   • B) Directional selection
   • C) Stabilizing selection
   • D) Balancing selection
5. 5.

   Which mode of natural selection acts against extreme phenotypic traits and favors intermediate individuals, thereby reducing overall phenotypic variation in a population?

   • A) Directional selection
   • B) Disruptive selection
   • C) Stabilizing selection
   • D) Frequency-dependent selection