Table of Contents

1
Table of Contents
Population Genetics and Speciation
Chapter 16

• Section 1 Genetic Equilibrium
• Section 2 Disruption of Genetic Equilibrium
• Section 3 Formation of Species

2
Standards
Chapter 16
Section 1 Genetic Equilibrium
SPI 3210.5.1 Compare and contrast the structural,
functional, and behavioral adaptations of animals
or plants found in different environments. SPI
3210.5.2 Recognize the relationship between form
and function in living things. SPI 3210.5.3
Recognize the relationships among environmental
change, genetic variation, natural selection, and
the emergence of a new species. SPI 3210.5.4
Describe the relationship between the amount of
biodiversity and the ability of a population to
adapt to a changing environment. SPI 3210.5.5
Apply evidence from the fossil record,
comparative anatomy, amino acid sequences, and
DNA structure that support modern classification
systems. SPI 3210.5.6 Infer relatedness among
different organisms using modern classification
systems.
3
Objectives
Section 1 Genetic Equilibrium
Chapter 16

• Identify traits that vary in populations and that
  may be studied.
• Explain the importance of the bell curve to
  population genetics.
• Compare three causes of genetic variation in a
  population.
• Calculate allele frequency and phenotype
  frequency.
• Explain Hardy-Weinberg genetic equilibrium.

4
Variation of Traits Within a Population
Section 1 Genetic Equilibrium
Chapter 16

• Population biologists study many different traits
  in populations, such as size and color.

5
Variation of Traits Within a Population, continued
Section 1 Genetic Equilibrium
Chapter 16

• Causes of Variation
• Traits vary and can be mapped along a bell curve,
  which shows that most individuals have average
  traits, whereas a few individuals have extreme
  traits.
• Variations in genotype arise by mutation,
  recombination, and the random pairing of gametes.

6
The Gene Pool
Section 1 Genetic Equilibrium
Chapter 16

• The total genetic information available in a
  population is called the gene pool.

7
The Gene Pool, continued
Section 1 Genetic Equilibrium
Chapter 16

• Allele frequency is determined by dividing the
  total number of a certain allele by the total
  number of alleles of all types in the population.

8
The Gene Pool, continued
Section 1 Genetic Equilibrium
Chapter 16

• Predicting Phenotype
• Phenotype frequency is equal to the number of
  individuals with a particular phenotype divided
  by the total number of individuals in the
  population.

9
The Hardy-Weinberg Genetic Equilibrium
Section 1 Genetic Equilibrium
Chapter 16

• Allele frequencies in the gene pool do not change
  unless acted upon by certain forces.
• Hardy-Weinberg genetic equilibrium is a
  theoretical model of a population in which no
  evolution occurs and the gene pool of the
  population is stable.

10
Phenotype Frequency
Section 1 Genetic Equilibrium
Chapter 16
11
Section 2 Disruption of Genetic Equilibrium
Chapter 16
Objectives

• List five conditions under which evolution may
  take place.
• Explain how migration can affect the genetics of
  populations.
• Explain how genetic drift can affect populations
  of different sizes.
• Contrast the effects of stabilizing selection,
  directional selection, and disruptive selection
  on populations over time.
• Identify examples of nonrandom mating.

12
Standards
Chapter 16
Section 1 Genetic Equilibrium
SPI 3210.5.1 Compare and contrast the structural,
functional, and behavioral adaptations of animals
or plants found in different environments. SPI
3210.5.2 Recognize the relationship between form
and function in living things. SPI 3210.5.3
Recognize the relationships among environmental
change, genetic variation, natural selection, and
the emergence of a new species. SPI 3210.5.4
Describe the relationship between the amount of
biodiversity and the ability of a population to
adapt to a changing environment. SPI 3210.5.5
Apply evidence from the fossil record,
comparative anatomy, amino acid sequences, and
DNA structure that support modern classification
systems. SPI 3210.5.6 Infer relatedness among
different organisms using modern classification
systems.
13
Section 2 Disruption of Genetic Equilibrium
Chapter 16
Mutation

• Evolution may take place when populations are
  subject to genetic mutations, gene flow, genetic
  drift, nonrandom mating, or natural selection.
• Mutations are changes in the DNA.

14
Section 2 Disruption of Genetic Equilibrium
Chapter 16
Gene Flow

• Emigration and immigration cause gene flow
  between populations and can thus affect gene
  frequencies.

15
Section 2 Disruption of Genetic Equilibrium
Chapter 16
Genetic Drift

• Genetic drift is a change in allele frequencies
  due to random events.
• Genetic drift operates most strongly in small
  populations.

16
Section 2 Disruption of Genetic Equilibrium
Chapter 16
Nonrandom Mating

• Mating is nonrandom whenever individuals may
  choose partners.

17
Section 2 Disruption of Genetic Equilibrium
Chapter 16
Nonrandom Mating, continued

• Sexual Selection
• Sexual selection occurs when certain traits
  increase an individuals success at mating.
• Sexual selection explains the development of
  traits that improve reproductive success but that
  may harm the individual.

18
Section 2 Disruption of Genetic Equilibrium
Chapter 16
Natural Selection

• Natural selection can influence evolution in one
  of three general patterns.

19
Section 2 Disruption of Genetic Equilibrium
Chapter 16
Natural Selection, continued

• Stabilizing Selection
• Stabilizing selection favors the formation of
  average traits.

20
Section 2 Disruption of Genetic Equilibrium
Chapter 16
Natural Selection, continued

• Disruptive Selection
• Disruptive selection favors extreme traits rather
  than average traits.

21
Section 2 Disruption of Genetic Equilibrium
Chapter 16
Natural Selection, continued

• Directional Selection
• Directional selection favors the formation of
  more-extreme traits.

22
Two Kinds of Selection
Section 2 Disruption of Genetic Equilibrium
Chapter 16
23
Section 3 Formation of Species
Chapter 16
Objectives

• Relate the biological species concept to the
  modern definition of species.
• Explain how the isolation of populations can lead
  to speciation.
• Compare two kinds of isolation and the pattern of
  speciation associated with each.
• Contrast the model of punctuated equilibrium with
  the model of gradual change.

24
Standards
Chapter 16
Section 1 Genetic Equilibrium
SPI 3210.5.1 Compare and contrast the structural,
functional, and behavioral adaptations of animals
or plants found in different environments. SPI
3210.5.2 Recognize the relationship between form
and function in living things. SPI 3210.5.3
Recognize the relationships among environmental
change, genetic variation, natural selection, and
the emergence of a new species. SPI 3210.5.4
Describe the relationship between the amount of
biodiversity and the ability of a population to
adapt to a changing environment. SPI 3210.5.5
Apply evidence from the fossil record,
comparative anatomy, amino acid sequences, and
DNA structure that support modern classification
systems. SPI 3210.5.6 Infer relatedness among
different organisms using modern classification
systems.
25
Section 3 Formation of Species
Chapter 16
The Concept of Species

• According to the biological species concept, a
  species is a population of organisms that can
  successfully interbreed but cannot breed with
  other groups.

26
Section 3 Formation of Species
Chapter 16
Isolation and Speciation

• Geographic Isolation
• Geographic isolation results from the separation
  of population subgroups by geographic barriers.

27
Section 3 Formation of Species
Chapter 16
Geographic Isolation
Click below to watch the Visual Concept.
28
Section 3 Formation of Species
Chapter 16
Isolation and Speciation, continued

• Allopatric Speciation
• Geographic isolation may lead to allopatric
  speciation.

29
Section 3 Formation of Species
Chapter 16
Isolation and Speciation, continued

• Reproductive Isolation
• Reproductive isolation results from the
  separation of population subgroups by barriers to
  successful breeding.

30
Section 3 Formation of Species
Chapter 16
Reproductive Isolation
Click below to watch the Visual Concept.
31
Section 3 Formation of Species
Chapter 16
Isolation and Speciation, continued

• Sympatric Speciation
• Reproductive isolation within the same geographic
  area is known as sympatric speciation.

32
Section 3 Formation of Species
Chapter 16
Rates of Speciation

• In the gradual model of speciation (gradualism),
  species undergo small changes at a constant rate.
  
• Under punctuated equilibrium, new species arise
  abruptly, differ greatly from their ancestors,
  and then change little over long periods.

33
Section 3 Formation of Species
Chapter 16
Comparing Punctuated Equilibrium and Gradualism