A new predator invades the habitat of a population of field...

A new predator invades the habitat of a population of field mice. Individuals with larger body size are easier for the predator to capture then individuals with smaller body size. Draw a histogram of body sizes with two plot lines, one showing the former population and another showing the new population that indicates how this population will likely evolve. On your histogram, also indicate what type of natural selection is occurring here.

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Key Concepts

Phenotypic Distribution

The phenotypic distribution refers to the range and frequency of observable traits, such as body size, within a population. In a histogram representing this distribution, the initial population might exhibit a normal distribution, while the population under directional selection will show a shift in the distribution curve towards the trait that confers a survival advantage—in this case, smaller body sizes.

Natural Selection

Natural selection is the process by which organisms with traits that are better adapted to their environment have improved survival and reproductive success. In this scenario, the presence of a new predator alters which traits are advantageous, leading to a change in the frequency of certain traits within the population over time.

Directional Selection

Directional selection occurs when natural selection favors one extreme phenotype over the other, causing a shift in the population's trait distribution. Here, individuals with smaller body sizes have a survival advantage because they are less likely to be captured by predators, resulting in an evolutionary shift towards smaller body sizes.

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