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Ch. 23 - Evolutionary Processes
Freeman - Biological Science 8th Edition
Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook
All textbooksFreeman 8th EditionCh. 23 - Evolutionary ProcessesProblem 9
Chapter 23, Problem 9

Draw a small concept map showing how selection, genetic drift, gene flow, and mutation relate to genetic variation.

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Step 1: Start by drawing a circle in the center of your paper and label it 'Genetic Variation'. This will be the main concept that all other concepts connect to.
Step 2: Draw four lines radiating out from the 'Genetic Variation' circle. At the end of each line, draw a circle and label them 'Selection', 'Genetic Drift', 'Gene Flow', and 'Mutation'. These are the four factors that contribute to genetic variation.
Step 3: Connect 'Selection' to 'Genetic Variation' with a line. Write on the line 'Natural selection can increase or decrease genetic variation in a population by favoring certain alleles over others'.
Step 4: Connect 'Genetic Drift' to 'Genetic Variation' with a line. Write on the line 'Genetic drift can cause random changes in allele frequencies, leading to genetic variation'.
Step 5: Connect 'Gene Flow' and 'Mutation' to 'Genetic Variation' with lines. Write on the 'Gene Flow' line 'Gene flow introduces new alleles into a population, increasing genetic variation'. Write on the 'Mutation' line 'Mutation creates new alleles, contributing to genetic variation'.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Natural Selection

Natural selection is the process by which certain traits become more common in a population due to their advantageous effects on survival and reproduction. Organisms with favorable traits are more likely to survive and reproduce, leading to an increase in those traits in subsequent generations. This mechanism plays a crucial role in shaping genetic variation by favoring alleles that enhance fitness.
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Genetic Drift

Genetic drift refers to random changes in allele frequencies within a population, particularly in small populations. These changes can lead to the loss of genetic variation over time, as certain alleles may become fixed or lost purely by chance. Genetic drift can significantly impact the evolutionary trajectory of a population, especially when combined with other mechanisms like selection.
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Gene Flow

Gene flow, or gene migration, is the transfer of genetic material between populations through the movement of individuals or their gametes. This process can introduce new alleles into a population, increasing genetic variation and potentially altering allele frequencies. Gene flow acts as a counterbalance to the effects of genetic drift and selection, promoting genetic diversity within and between populations.
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Related Practice
Textbook Question

In the 1700s and 1800s, royalty in Europe often married their close relatives; furthermore, recessive genetic diseases such as hemophilia showed up much more often among royals than in the general population. Explain the likely connection.

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Textbook Question

Determine what is incorrect in the following statement: Deer mice living on beaches mutated their genes so that they could have white fur color, providing better camouflage to survive on beaches.

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Textbook Question

In humans, albinism is caused by loss-of-function mutations in genes involved in the synthesis of melanin, the dark pigment in skin. Only people homozygous for a loss-of-function allele (genotype 𝑎𝑎) have albinism. In one study of an American population, individuals with albinism were present at a frequency of about 1 in 10,000 (or 0.0001). Assuming that genotypes are in Hardy–Weinberg Equilibrium, what is the predicted frequency of individuals who are carriers (that is, 𝐴𝑎) for the albinism allele?

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Textbook Question

Suppose you were a conservation biologist working to preserve two populations of monkeys. The first population has 5000 individuals, while the second population has 50,000 individuals. Which population do you expect to have higher genetic diversity? Consider which evolutionary process(es) may be different between these populations. Justify your response.

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Textbook Question

Human activities are causing the fragmentation of the Brazilian Atlantic rain forest. One result is that toucans have become extinct or nearly extinct in some of the forest fragments. Does the absence of toucans affect the forest?

Toucans disperse seeds of key forest species such as juçara palms by eating the fruit and defecating the seeds in new locations, sometimes more than a kilometer away. If there are no toucans, is the genetic diversity of palms likely to increase or decrease within forest fragments? Why?

a. Increase (due to increased genetic drift)

b. Decrease (due to decreased gene flow)

c. Decrease (due to decreased mutation rate)

d. Decrease (due to decreased natural selection)

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