Chapter 15.3, Problem 7MI

Summary Introduction

To compare:

Natural selection and sexual selection by completing the given table.

Introduction:

Charles Darwin in his theory of natural selection proposed that natural selection could modify a population to produce new species. The allelic frequencies in a population’s gene pool will change over generations due to natural selection of variations.

Answer to Problem 7MI

	Species Changes Based on	Increases Fitness?
Natural selection	Environment	Yes
Sexual selection	Competition for a mate	Not always

Explanation of Solution

Natural selection- There are four principles of the theory of natural selection:

1. Individual in a population show differences called variations.
2. Variations can be inherited; i.e they can be passed down from parent to offspring.
3. Organisms produce more offspring than can survive on available resources.
4. Variations that increase reproductive success will have a greater chance of being passed on than those that do not increase reproductive success.

In this way new species can be introduced into nature. Naturalselection can introduce new species into the environment by promoting favorable traits.It selects the individuals that are best adapted for survival and reproduction.

Sexual selection- This is a type of selection which functions in a population where males and females are quite different in appearance. Usually males are largest and most colorful in the population. Some males even develop threatening features that intimidate other males. For example the peacocks with largest tails tend to attract more peahens. The frequency of this trait increases because of sexual selection. However these traits may not always increase fitness of the species. Although sexual selection is not considered a form of natural selection it follows the same principle; i.e it enhances reproductive success.