10.3.1 Variations Within and Between Populations

Question 1

variations

Answer 1

• Variation between individuals is the raw material for natural selection.
• Variation—such as polymorphisms—can occur within a population.
• The two main sources of variation are:
1. mutation
2. sexual recombination

Question 2

note

Answer 2

• Review: A population is a group of organisms that belong to the same species and live in the same geographical area.
• The illustration on the left depicts the fact that variation exists in populations. The existence of two or more inherited forms in a population is called polymorphism. A balanced polymorphism is present when two or more
  inherited forms of a trait are maintained in a population at constant frequencies over time.
• Variation between individuals is the raw material for natural selection.
• The major sources of variation in populations are mutation and sexual recombination.
• A mutation occurs as a result of a change in an organism’s DNA.
• Sexual recombination is the appearance of new gene
  combinations. Recombination can occur during meiosis,
  either by crossing over or by the formation of new
  chromosome combinations.

Question 3

Which of the following is not an example of polymorphism?

Answer 3

• dolphins and porpoises

Question 4

Natural selection can decrease the diversity of a population by favoring one allele over another. However, in some cases, natural selection may enhance the genetic diversity of a population. The ability of natural selection to promote diversity in a population is called

Answer 4

• balanced polymorphism.

Question 5

True or false?

All variation within a population is heritable.

Answer 5

• false

Question 6

What is one of the direct causes of genetic variation?

Answer 6

• mutation

Question 7

Beak size in the black-bellied seed cracker (a bird) is an example of what?

Answer 7

• balanced polymorphism

Question 8

The existence of two or more phenotypic forms in a population is called

Answer 8

• polymorphism