Question

In a species, the weight of newborn ranges from 2 to 5 kg. 97% of the newborn with an average weight between 3 to 3.3 kg survive whereas 99% of the infants born with weights from 2 to 2.5 kg or 4.5 to 5 kg die. Which type of selection process is taking place?

• A. Directional Selection
• B. Stabilizing Selection
• C. Disruptive Selection
• D. Cyclical Selection

Answer 1

The Correct Option is B

The question is about determining the type of selection process occurring in a species based on the survival rate of newborns with different weight ranges. Let's analyze the given data:

1. The weight of newborns ranges from 2 to 5 kg.
2. 97% of newborns with an average weight between 3 and 3.3 kg survive.
3. 99% of newborns with weights from 2 to 2.5 kg or from 4.5 to 5 kg die.

We need to identify which type of selection process this scenario represents. Let's examine each option:

• Directional Selection: In directional selection, one extreme phenotype is favored over the others, causing the population's phenotype distribution to shift in one direction. This is not applicable here, as the middle weight range is favored, not one of the extremes.
• Stabilizing Selection: This type of selection favors the average phenotypes and reduces the variance, thereby stabilizing the population around a particular trait value. In this scenario, newborns with weights around the average (3 to 3.3 kg) survive best, which highlights stabilizing selection.
• Disruptive Selection: Disruptive selection favors extreme values of a trait, favoring individuals at either end of the spectrum and against those with intermediate traits. This does not fit the scenario as the extremes (2 to 2.5 kg and 4.5 to 5 kg) have higher mortality rates.
• Cyclical Selection: Cyclical selection refers to the selection that changes regularly (e.g., seasonally), typically favoring different traits at different times. This option does not apply based on the provided data.

After considering all options, the survival of newborns with an average weight between 3 and 3.3 kg aligns with Stabilizing Selection because it favors those with moderate weight ranges while reducing the survival of both extremes.

Therefore, the correct answer is: Stabilizing Selection.