Chapter 16, Problem 1AC

In North America, the average height of adult humans has been increasing steadily for decades. Is directional selection occurring? What data would justify your answer?

Summary Introduction

To determine:

The occurrence of directional selection in North America, as the average height of adult humans has been increasing steadily for decades.

Introduction:

Alteration in the frequency distribution of heritable traits occurs by three means, which depends on the phenotype that is favored by natural selection in a population. Three modes of natural selection are; disruptive selection, directional selection, and stabilizing selection.

Explanation of Solution

In a population, one extreme trait is favored by directional selection, and population tends to move in direction of that particular trait against the other average traits. Sexual selection is a type of selection in which individual of one sex prefers to mate with individual of other sex on the basis of their morphological characters; height, boldness, brightness, and strong body.

As in North America the average height of adult humans has been increasing steadily for decades, it shows that the individual with longer height are more likely pick up as partners by the individual of other sex. Hence, the increase in average height shows the occurrence of sexual selection in population.

Summary Introduction

To determine:

The data that justify that, in North America the average height of adult humans has been increasing steadily for decades shows the occurrence of sexual selection in population.

Introduction:

There are three modes of natural selection; disruptive selection, directional selection, and stabilizing selection, through which frequency distribution of heritable traits can be altered depending upon the phenotype, which is favored in a population

Explanation of Solution

Mating success among the individuals of a population determine the sexual selection of a particular trait, and it is mostly depends on the female.

A survey was conducted in North America in order to check the partner preference in humans, and it was observed that; females tend to prefer a male partner with longer height.

Mating with longer height male increases the chances that offspring will receive trait of longer height, thus the population shows steadily increase in average height, in North America.

Conclusion

In North America, as the average height of adult humans has been increasing steadily for decades, shows the sexual selection among the population.