Ch 23: Campbell Biology Chapter 23: The Evolution of Populations
About This Chapter
How It Works:
- Identify the lessons in the Campbell Biology Evolution of Populations chapter with which you need help.
- Find the corresponding video lessons with this companion course chapter.
- Watch fun videos that cover the evolution of populations topics you need to learn or review.
- Complete the quizzes to test your understanding.
- If you need additional help, rewatch the videos until you've mastered the material or submit a question for one of our instructors.
Students will learn:
- Sources of genetic variation
- The Hardy-Weinberg equilibrium equation
- How an evolutionary agent is defined
- Kinds of genetic drift
- Causes of microevolution
- Different kinds of natural selection
- Forms of sexual selection
- Types of balancing selection
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1. What Is Genetic Variation? - Sources, Definition & Types
Natural selection is the process that drives evolution, but what drives natural selection? Genetic variation increases the genetic diversity in and among populations, allowing for new traits to become more or less prominent in the gene pool.

2. Hardy-Weinberg Equilibrium I: Overview
In this lesson, we'll examine population genetics in greater detail. We'll also explore notions of Hardy-Weinberg equilibrium for large, stable populations. Is the genetic makeup of our flying hamster population changing? The Hardy-Weinberg equilibrium can serve as a reference point as we try to answer population genetics questions.

3. Hardy-Weinberg Equilibrium II: The Equation
The Hardy-Weinberg equilibrium equation is represented by a polynomial, so we'll have to do some calculations. Don't be intimidated; a few coin tosses can help us make sense of allelic frequencies in a given gene pool.

4. Hardy-Weinberg Equilibrium III: Evolutionary Agents
In this lesson, you'll learn how the Hardy-Weinberg equation relates to different evolutionary agents and population changes. Discover how the equation may be used to discover populations that are not in equilibrium.

5. Genetic Drift: Definition, Examples & Types
Genetic drift reduces genetic variability of a population by decreasing the size of the population. The change in population size and variability often leads to new species and unique populations.

6. Causes of Microevolution: Natural Selection, Gene Flow & Genetic Drift
Environments are dynamic, which causes populations to be as well. In this lesson, you'll learn about microevolution, as well as the mechanisms behind it that cause changes in allele frequencies within populations.

7. Natural Selection: Definition, Types & Examples
We'll take a look at the types of natural selection that can occur. From flying hamsters to moths, you'll start to grasp the different paths organisms can take as they respond to their changing environments over time.

8. Sexual Selection: Definition & Forms
Why are you attracted to someone? One reason may be due to the forces of sexual selection. This lesson will explain sexual selection and will investigate types of sexual selection.

9. Balancing Selection: Heterozygote Advantage & Frequency-Dependent Selection
You may have heard of natural selection, but what about balancing selection? This lesson will cover two important mechanisms that help keep genes in a population, which is important to populations if they don't want to become extinct!
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Other Chapters
Other chapters within the Campbell Biology: Online Textbook Help course
- Campbell Biology Chapter 1: The Themes of Biology, and Scientific Inquiry
- Campbell Biology Chapter 2: The Chemical Context of Life
- Campbell Biology Chapter 3: Water and Life
- Campbell Biology Chapter 4: Carbon and the Molecular Diversity of Life
- Campbell Biology Chapter 5: The Structure and Function of Large Biological Molecules
- Campbell Biology Chapter 6: A Tour of the Cell
- Campbell Biology Chapter 7: Membrane Structure and Function
- Campbell Biology Chapter 8: An Introduction to Metabolism
- Campbell Biology Chapter 9: Cellular Respiration and Fermentation
- Campbell Biology Chapter 10: Photosynthesis
- Campbell Biology Chapter 11: Cell Communication
- Campbell Biology Chapter 12: The Cell Cycle
- Campbell Biology Chapter 13: Meiosis and Sexual Life Cycles
- Campbell Biology Chapter 14: Mendel and the Gene Idea
- Campbell Biology Chapter 15: The Chromosomal Basis of Inheritance
- Campbell Biology Chapter 16: The Molecular Basis of Inheritance
- Campbell Biology Chapter 17: Gene Expression: From Gene to Protein
- Campbell Biology Chapter 18: Regulation of Gene Expression
- Campbell Biology Chapter 19: Viruses
- Campbell Biology Chapter 20: DNA Tools and Biotechnology
- Campbell Biology Chapter 21: Genomes and Their Evolution
- Campbell Biology Chapter 22: Descent With Modification: A Darwinian View of Life
- Campbell Biology Chapter 24: The Origin of Species
- Campbell Biology Chapter 25: The History of Life on Earth
- Campbell Biology Chapter 26: Phylogeny and the Tree of Life
- Campbell Biology Chapter 27: Bacteria and Archaea
- Campbell Biology Chapter 28: Protists
- Campbell Biology Chapter 29: Plant Diversity I
- Campbell Biology Chapter 30: Plant Diversity II
- Campbell Biology Chapter 31: Fungi
- Campbell Biology Chapter 32: An Overview of Animal Diversity
- Campbell Biology Chapter 33: An Introduction to Invertebrates
- Campbell Biology Chapter 34: The Origin of Evolution of Vertebrates
- Campbell Biology Chapter 35: Plant Structure, Growth, and Development
- Campbell Biology Chapter 36: Resource Acquisition and Transport in Vascular Plants
- Campbell Biology Chapter 37: Soil and Plant Nutrition
- Campbell Biology Chapter 38: Angiosperm Reproduction and Biotechnology
- Campbell Biology Chapter 39: Plant Responses to Internal and External Signals
- Campbell Biology Chapter 40: Basic Principles of Animal Form and Function
- Campbell Biology Chapter 41: Animal Nutrition
- Campbell Biology Chapter 42: Circulation and Gas Exchange
- Campbell Biology Chapter 43: The Immune System
- Campbell Biology Chapter 44: Osmoregulation and Excretion
- Campbell Biology Chapter 45: Hormones and the Endocrine System
- Campbell Biology Chapter 46: Animal Reproduction
- Campbell Biology Chapter 47: Animal Development
- Campbell Biology Chapter 48: Neurons, Synapses, and Signaling
- Campbell Biology Chapter 49: Nervous Systems
- Campbell Biology Chapter 50: Sensory and Motor Mechanisms
- Campbell Biology Chapter 51: Animal Behavior
- Campbell Biology Chapter 52: An Introduction to the Ecology of the Biosphere
- Campbell Biology Chapter 53: Population Ecology
- Campbell Biology Chapter 54: Community Ecology
- Campbell Biology Chapter 55: Ecosystems and Restoration Ecology
- Campbell Biology Chapter 56: Conservation Biology and Global Change