Question

Which of the following statements regarding mutations is correct? a. Mutations are not important in evolution. b. Mutations provide a source of genetic variation, but other evolutionary factors are more important in determining allele frequencies in a population. c. Mutations occur at such a high rate that they promote major changes in the gene pool from one generation to the next. d. Mutations are of greater importance in smaller populations than in larger ones. e. Mutations are of greater importance in larger populations than in smaller ones.

Short answer

The fits most correct statement is B. Mutations provide a source of genetic variation, but other evolutionary factors are more important in determining allele frequencies in a population.

Step-by-step solution

Clarifying the concept of mutations

Mutations are changes in the DNA sequence and they are important because they bring about genetic variation. This is the raw material upon which evolutionary forces like natural selection can act.

Understanding the impact of mutations on allele frequencies

While mutations do provide a source of genetic variation, the rate of mutations is generally low. Thus, they don't promote major changes in the gene pool from one generation to the next. Other factors like natural selection, genetic drift, and gene flow often play more significant roles in determining allele frequencies.

Evaluating the importance of mutations in different population sizes

In smaller populations, individual mutations may have a greater effect because there are fewer individuals and thus less genetic variation. In larger populations, where there's more genetic variation, a single mutation may not have as strong effect. Therefore, one could argue that mutations are, in general, of great importance in both, but their effect could be more noticeable in smaller populations.

Key concepts

Genetic Variation

Genetic variation is the variety of different genetic compositions within a population. It is a critical cornerstone of biological diversity and is largely responsible for the differences between individuals of a species. This variation occurs due to mutations, which are changes in DNA sequences. These changes can introduce new traits into a population, offering a pool of possibilities upon which natural selection and other evolutionary forces can act.

Genetic variation is crucial for the health and adaptability of populations. Without it, populations would not be able to evolve to cope with changes in the environment. For example, when a new disease appears, a genetically varied population will have individuals who might be naturally resistant, thereby ensuring the survival of the population as a whole. To summarize, genetic variation is the foundation upon which evolution is built, providing the raw material for all evolutionary processes.

Allele Frequencies

Allele frequencies refer to how common an allele is in a population. An allele is simply different forms of a gene that determine specific traits. Tracking how frequently these alleles occur in a population is important to understand how populations change over time due to evolutionary forces.

Formally, the allele frequency is calculated as the ratio of the number of times an allele appears in the population to the total number of alleles for that gene. This can be expressed by the formula:
\[f(a) = \frac{{\text{number of copies of allele a}}}{{\text{total number of alleles in the population}}}\]
Changes in allele frequencies are indicative of evolution in action. These changes can occur gradually or suddenly, driven by processes such as mutation, natural selection, genetic drift, and migration. By studying allele frequencies, scientists can gain insights into the genetic health and evolutionary potential of populations.

Evolutionary Forces

Evolutionary forces are mechanisms that cause changes in allele frequencies within populations over time. These include natural selection, mutation, genetic drift, and gene flow. Each plays a distinct role in shaping the genetic landscape of populations.

- **Natural selection** acts on genetic variation, favoring traits that provide an advantage in survival and reproduction. Over generations, beneficial alleles increase in frequency, shaping the population's genetic structure.
- **Mutation** introduces new genetic variations by randomly altering DNA sequences. While the mutation rate is usually low, it is essential for providing new alleles that might be beneficial under changing environmental conditions.
- **Genetic drift** is the random fluctuation of allele frequencies. It has a more pronounced effect in smaller populations, where chance events can lead to significant changes in genetic makeup.
- **Gene flow** refers to the transfer of alleles between populations through migration. This process can introduce new alleles into a population and increase genetic variation.

Together, these evolutionary forces drive the dynamic processes of evolution, highlighting the constant interplay between genetics and the environment.

Population Size

Population size plays a pivotal role in shaping the genetic structure of populations. It can influence the effectiveness of evolutionary forces such as genetic drift and the usual impact of mutations.

In small populations, genetic drift can have a large impact because random events can significantly alter allele frequencies. This means that beneficial alleles can be lost and deleterious alleles can spread purely by chance. Furthermore, individual mutations might have more noticeable impacts because there are fewer individuals to "buffer" the effect of any one change.

In larger populations, the effects of genetic drift are lessened because the larger number of individuals buffers against the random loss or fixation of alleles. However, with more individuals, there is more genetic diversity overall, which can lead to a greater capacity to adapt to environmental changes. In large populations, mutations can spread wider but have to compete with a larger background of variation. Therefore, understanding population size is essential when considering how populations evolve over time.