Question

In a population of fish, body coloration varies from a light shade, almost white, to a very dark shade of green. If changes in the environment resulted in decreased predation of individuals with the lightest coloration, this would be an example of ____________ selection. a. diversifying b. stabilizing c. directional d. sexual e. artificial

Short answer

The selection happening in the described situation is c. directional.

Step-by-step solution

Understand the given scenario

The given situation is that the fish population's body coloration varies from a light shade, almost white, to a very dark shade of green. Changes in the environment decreased the predation of individuals with the lightest coloration.

Apply selection definitions

Look at the situation and apply selection type definitions. Given that there seems to be a shift favoring a specific trait (lightest coloration), this signals a type of selection that favors one extreme phenotype.

Determine the type of selection

Based on the definitions, it can be concluded that the situation describes a directional selection, as it favors one phenotype extreme (light coloration).

Key concepts

Natural Selection

Natural selection is a fundamental mechanism of evolution that was first articulated by Charles Darwin. It is the process by which certain traits become more common in a population over successive generations. This occurs because individuals with traits that are advantageous for survival and reproduction are more likely to pass on their genes to the next generation.

Imagine a scenario where in a particular environment, predators can easily spot and prey on fish that are darker in color. Over time, the fish population will likely have more individuals with lighter coloring, as these fish would evade predators more successfully, hence increase their chances to reproduce. This process, driven by environmental factors, where certain traits become more prevalent, exemplifies natural selection.

Phenotype Variation

Phenotype variation refers to the differences in physical and physiological traits among individuals of a species. These traits are observable and can include things like body color, beak shape, or leaf size. This variation is crucial as it provides the material upon which natural selection can act.

For instance, in a population of fish where body color ranges from light to dark shades, phenotype variation exists in terms of coloration. If environmental pressures influence the success of certain colors more than others, then natural selection can act on this variation to shift the population's traits over time. Without this variation, there would be no material for natural selection to work on.

Evolutionary Biology

Evolutionary biology is the branch of science that studies the origins, changes, and continuities of life on Earth. The field explores how species evolve over time through mechanisms such as mutation, genetic drift, and natural selection. Fundamental to evolutionary biology is the understanding that all living organisms share a common ancestor and have diversified over time due to natural evolutionary processes.

In the case of our fish population, evolutionary biology would examine how the change in environment that favors lighter-colored fish is a part of the broader evolutionary pattern, and how these changes may lead to speciation or the emergence of new species, over many generations. The adjustment to environmental conditions through natural selection is a cornerstone concept in the evolutionary biology narrative.

Population Genetics

Population genetics is the study of the distribution and changes of allele frequencies in a population, as such changes affect genetic diversity. It bridges the gap between evolutionary theory and genetic inheritance, and includes the examination of gene distribution, mutation, genetic drift, and natural selection.

From a population genetics perspective, the decrease in predation for lighter colored fish would lead to an increase in alleles coding for lighter coloration in the gene pool. Consequently, the population's genetic makeup may shift over time as these advantageous alleles increase in frequency, an event well-explained by population genetics principles. The study of how these allele frequencies change, in response to environmental pressures, forms an integral part in understanding the evolution of populations.