Question

The theory of natural selection does not explain ______. a. genetic drift b. the founder effect c. gene flow d. how mutations arise e. inheritance f. any of the above

Short answer

Natural selection does not explain how mutations arise (Option d).

Step-by-step solution

Understand the Theory of Natural Selection

The theory of natural selection, proposed by Charles Darwin, explains how species evolve over generations. It suggests that traits that enhance survival and reproduction become more common in successive generations because individuals with those traits are more likely to survive and reproduce.

Identify the Scope of Natural Selection

Natural selection explains the adaptation of organisms to their environment, the survival of the fittest, and the process by which advantageous traits increase an organism's chances of survival and reproduction.

Analyze the Given Options

Review the options provided: genetic drift, the founder effect, gene flow, how mutations arise, and inheritance. Consider whether each option falls under the processes explained by natural selection.

Determine What Natural Selection Does Not Explain

Natural selection does not explain the origin of new variations or genetic mutations. It operates on existing variation within a population. Therefore, the process by which mutations arise, which is random and not adaptive, is not explained by natural selection.

Key concepts

Genetic Drift

Genetic drift refers to random changes in the frequency of alleles (variations of a gene) within a population. Unlike natural selection, which relies on the survival advantage of particular traits, genetic drift is non-selective and can happen purely by chance. For instance, in a small population, if a few individuals fail to reproduce due to random events, such as a natural disaster, the genetic composition of the ensuing generations could dramatically shift.

Key points to understand about genetic drift:

• It is more significant in small populations where random events can have a larger impact.
• Genetic drift can lead to the loss of genetic variation within a population.
• Unlike natural selection, genetic drift does not necessarily lead to adaptations that provide a survival advantage.

Understanding genetic drift is crucial as it highlights the role of chance in evolution, demonstrating that not all aspects of a species’ evolution are driven by advantageous traits.

Founder Effect

The founder effect is a special case of genetic drift. It occurs when a small group breaks off from a larger population to establish a new colony. Because this group is so small, the genetic diversity is reduced — meaning the new population may have different allele frequencies than the original larger population. This can lead to unique traits being more prevalent within the smaller group. The founder effect is notable for several reasons:

• It can create populations with decreased genetic variation.
• The specific traits and genetic makeup of the "founder" individuals heavily influence the new population.
• This effect can lead to increased prevalence of certain genetic disorders.

Instances of the founder effect are observed in island populations or isolated human communities. These populations may exhibit unique evolutionary paths due to their restricted gene pool.

Mutations

Mutations are changes in the DNA sequence of a cell's genome, and they are fundamental to genetic variation. These changes can occur randomly and are not directly explained by natural selection, as mutations can be harmful, beneficial, or neutral. Natural selection acts upon this variation, promoting traits that enhance survival.

Important features of mutations:

• Mutations can occur spontaneously due to errors in DNA replication or be induced by external factors (radiation, chemicals).
• They are the primary source of new genetic material in a population, fueling evolutionary processes.
• Mutations create genetic diversity, which is essential for adaptation and long-term survival of species.

While mutations themselves are random, natural selection can increase or decrease their occurrence within a population based on how they affect individuals’ fitness. Understanding mutations is key to recognizing how new traits can emerge and become prevalent within populations.