How Disruptive Selection Favors Organisms with Extreme Traits

Subject : Biology

Question:

Which organisms are most likely to survive in a population in which disruptive selection is occurring?

A. organisms that have average traits

B. organisms that have extreme traits

C. organisms that have the greatest number of offspring

D. organisms that are the largest and strongest

Expert Verified Solution:

The correct answer is B. organisms that have extreme traits. Disruptive selection is a type of natural selection that favors individuals with traits at both extremes of a spectrum rather than those with average or intermediate traits. In a population undergoing disruptive selection, organisms with extreme characteristics are more likely to survive and reproduce successfully, while those with average traits are selected against and may become less common over time.

 Explanation:

Disruptive selection occurs in environments where the conditions or resources create a selective pressure that makes it advantageous for individuals at the two extremes of a trait to survive better than those with intermediate traits. For example:

In a population of birds that feed on seeds, disruptive selection could occur if there are only very large or very small seeds available. Birds with large beaks are more efficient at cracking large seeds, while birds with small beaks are better at eating small seeds. Birds with medium-sized beaks, however, struggle to crack either type of seed and are less likely to survive and reproduce. Over time, this selective pressure causes the population to diverge, favoring birds with either very large or very small beaks, while medium-beaked birds diminish in number.

Organisms with extreme traits have a better chance of exploiting specific resources or surviving in specialized niches within the environment. In disruptive selection, the extremes thrive because the environment creates distinct advantages for these traits, while individuals with average traits may be less adapted to the available conditions. This can lead to an increase in genetic diversity, and in some cases, it may even contribute to speciation—the formation of new species from a single population.

The other options, such as organisms with average traits (A), organisms that have the greatest number of offspring (C), or organisms that are the largest and strongest (D), may not apply in the case of disruptive selection. While those traits might be advantageous in different selection scenarios, disruptive selection specifically promotes survival and reproduction of individuals at the extremes of a population’s trait distribution.

Disruptive selection drives evolutionary change by favoring organisms with extreme traits over those with intermediate traits, which can significantly alter the genetic makeup and diversity of a population over time.