Chapter 15, Problem 26A

Solution

To determine:

The type of Natural Selection represented by the graph.

Introduction:

The theory of natural selection was given by Charles Darwin and Alfred Wallace in 1858 and this theory is also known as Darwin-Wallace theory.

Natural selection is differential reproduction which means some members of population have genes that enable them to grow up and reproduce at higher rate and leave more surviving offspring in the next generation than others. It will result the gene to become predominant in the gene pool as it is producing more offspring that continue for many generations.

Natural selection can be of three types namely stabilizing. Disruptive and directional.

Stabilizing selection: This type of selection favors the intermediate forms and eliminates the extreme variants.

Disruptive selection: This type of selection favors more adaptable phenotypes instead of the average one. So, it is just opposite to stabilizing selection.

Directional selection: This type of selection produces a regular change in population in one direction in respect to certain characteristics. It favors the individuals that change in response to the environmental change and best adapted to new environment.

The graph shows the directional type of selection.