10.1.1 Population Genetics: Darwin Meets Mendel

Question 1

Darwin meets Mendel

Answer 1

• Charles Darwinand Gregor Mendel’stheories provide a working template for understanding the evolution of populations.
• Darwin’s theory of evolution by natural selection predicts how populations can change over time, but it does not explain how traits are inherited.
• Mendel’s theory of inheritance proposed that discrete units (later called genes) contain hereditary information.
• Population genetics is a modern discipline (1930s) that synthesizes Mendelian genetics and Darwin’s theory of natural selection

Question 2

Evolution

Answer 2

• the change in a population’s gene pool from
  one generation to the next.
• Review: According to Darwin’s theory of evolution by
  natural selection, populations change over time when selection favors individuals with certain characteristics over others.
  The components of the theory are as follows:
  1. Variation—Individual members of a population may differ in their characteristics.
  2. Reproductive advantage—Individuals with favored traits have a reproductive advantage.
  3. Selection—The environment selects individuals with a reproductive advantage, allowing them to contribute more offspring to the population.
  4. Population changes—Selection causes the relative frequency of traits to change over time

Question 3

note

Answer 3

• Darwin’s theory of natural selection was not well accepted by his peers because he could not adequately explain how traits are inherited. Darwin’s contemporary, Gregor Mendel experimentally determined the mechanism by which traits are inherited. However, Darwin and his peers overlooked the importance of Mendel’s work.
• Based on a series of experiments performed on pea plants, Mendel determined that discrete units, now called genes, controlled traits. Mendel’s experimentation concentrated on traits that varied in an either/or manner. An example is green versus yellow flower color. Proponents of Darwin’s theory argued that Mendelian inheritance could not explain how natural selection acted on subtle variations between individuals.
• Darwin stressed quantitative characters, which are
  characteristics that vary along a continuum. An example is skin color in humans. The proposed mechanism of
  inheritance did not explain how a selected characteristic could be maintained in a population. Modern geneticists now understand that Darwin’s quantitative characteristics are produced by multiple genes affecting a single trait.
• By the 1930s, the field of population genetics resolved the previous disparity between Darwin’s theory and Mendelian genetics.
• Population geneticists recognize that traits are inherited in discrete units and provide the variation upon which natural selection acts. They determined that Darwin’s quantitative characters are actually controlled by discrete units and are subject to the forces of natural selection.

Question 4

__________are characteristics that vary along a continuum.

Answer 4

• Quantitative characters

Question 5

True or false?

The change in a population’s gene pool from one generation to the next is evolution.

Answer 5

• true

Question 6

The modern discipline that synthesizes Mendelian genetics and Darwin’s theory of natural selection is called __________.

Answer 6

• population genetics

Question 7

Which of the following statements about genetic variation is not true?

Answer 7

• Genetic variation is always polygenic.

Question 8

Which of the following statements correctly describes a gene pool?

Answer 8

• A gene pool is the total of all alleles present in a population.

Question 9

Match the following description with the appropriate school of thought and choose the correct order of answers.

Answer 9

• b, d, c, a

Question 10

According to Darwin’s theory of natural selection,

Answer 10

• a population changes over time when individuals differ in their ability to survive and reproduce under particular environmental conditions.

Question 11

Darwin’s theory of natural selection was not well accepted by his peers because

Answer 11

• science lacked an explanation of the mechanism by which traits were inherited.

Question 12

True or false?

Quantitative characters are actually controlled by discrete units.

Answer 12

• true

Question 13

Which of the following best explains why natural selection must act with genetic variation to produce evolution?

Answer 13

• Natural selection provides conditions in which certain types of genetic variation are favored over others.