Question

Kimura's proposal regarding neutral variation differs from Darwinian evolution in that a. natural selection does not exist. b. most of the genetic variation in a population is due to mutations that do not affect reproductive success. c. neutral variation alters survival and reproductive success. d. neutral mutations are not affected by population size. e. it differs with respect to both b and c.

Short answer

The correct answer is b. Most of the genetic variation in a population is due to mutations that do not affect reproductive success.

Step-by-step solution

Understanding the Concepts

Kimura's neutral variation refers to the idea that most genetic mutations are neutral, and do not affect an organism's ability to survive or reproduce. In contrast, Darwinian evolution is the theory that natural selection, where individuals with advantageous traits have higher reproductive success, drives evolution.

Evaluation of Options

Analyze each of the provided options in the context of these definitions.

Eliminate Incorrect Options

Option a is incorrect since both theories acknowledge natural selection. Option c is wrong as neutral variation does not impact survival and reproductive success. Option d is incorrect, as neutral mutations can be affected by population size in terms of genetic drift.

Select the Correct Option

Option b is correct, as it aligns with Kimura's theory that most genetic variation is due to mutations that do not affect reproductive success.

Key concepts

Genetic Drift

Genetic drift is a fundamental concept in population genetics. It describes random changes in the frequency of genetic traits or alleles within a small population. Unlike natural selection, which is driven by environmental pressures and survival advantages, genetic drift occurs by chance. This means certain alleles can become more or less common, or even disappear entirely, simply due to random events.

Think of genetic drift like flipping a coin. In a small population, the outcomes of these coin flips can significantly impact which alleles are passed down to the next generation. Here are a few key points about genetic drift:

• It is more pronounced in small populations because fewer individuals mean random events have a bigger impact.
• Over time, genetic diversity can decrease because alleles can be lost due to chance alone.
• Genetic drift can lead to different traits becoming dominant that don’t necessarily provide a survival advantage.

Understanding genetic drift is crucial when studying evolution because it demonstrates how populations can change in unpredictable ways through random processes.

Natural Selection

Natural selection is often at the core of what people think about when discussing evolution. Proposed by Charles Darwin, this mechanism suggests that traits which enhance survival and reproduction become more common in a population over time. Natural selection is driven by environmental factors that affect which individuals are more likely to survive and reproduce.

Here are some important aspects of natural selection:

• Variation: Individuals within a species have slight differences due to genetic variation.
• Competition: Resources such as food, space, and mates are limited, leading to competition among individuals.
• Survival of the Fittest: Traits that improve an individual's chance of surviving and reproducing will likely be passed on to the next generation.

Natural selection explains how species adapt over generations to fit their environments better. It's a slow and continuous process that contributes significantly to the complexity of life on Earth.

Mutations

Mutations are changes that occur in the DNA sequence of an organism. They are a primary source of genetic variation, which is essential for evolution. Mutations can occur due to various factors such as errors during DNA replication or exposure to certain environmental influences like radiation or chemicals.

It's important to understand the different types of mutations and their effects:

• Neutral Mutations: These are changes that do not affect an organism's ability to survive or reproduce. They are often the main focus of the neutral theory of evolution.
• Beneficial Mutations: These provide some advantage to the organism, possibly leading to increased survival or reproductive success.
• Harmful Mutations: These can negatively impact an organism's fitness and are often weeded out by natural selection.

While most mutations are neutral or harmful, beneficial mutations are vital for adaptive evolution, allowing populations to better suit their environments over time.

Darwinian Evolution

Darwinian evolution, also known simply as evolution by natural selection, is a theory that describes the process by which species change and adapt over time. First introduced by Charles Darwin in the 19th century, it proposes that individuals with traits better suited to their environments are more likely to survive and reproduce, passing those traits to the next generation.

Key components of Darwinian evolution include:

• Descent with Modification: All species descend from common ancestors, but with changes or modifications over time.
• Common Descent: This concept suggests that all living organisms are related through a common lineage.
• Adaptation: Through natural selection, populations become better adapted to their environments.

While Darwin's theory was groundbreaking in explaining the process of evolution, it has been expanded upon with new scientific discoveries, including genetics, providing a more comprehensive understanding of how life evolves.