Question

Identify which type of natural selection is described in each case below.


Results in the evolution of the species:

Results in new species:

Favors traits at the two extremes:

No increase in diversity:

One extreme trait is favored:

Diversity decreases:

Diversity increases:

Answer 1

- Results in the evolution of the species: Directional selection — it shifts the population mean toward one trait value over time, changing allele frequencies.
- Results in new species: Disruptive selection — by favoring extremes and splitting a population, it can promote reproductive isolation and speciation.
- Favors traits at the two extremes: Disruptive selection — individuals at both extremes have higher fitness than intermediates.
- No increase in diversity: Directional selection — the mean shifts toward one extreme; diversity is not increased (often reduced).
- One extreme trait is favored: Directional selection — selection pushes the trait distribution toward one extreme.
- Diversity decreases: Stabilizing selection — intermediates are favored and extremes are removed, reducing variation.
- Diversity increases: Disruptive selection — selection for both extremes increases variation within the population.