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Ch 18: Evolution Overview

About This Chapter

Watch video lessons and refresh your knowledge of the theory of evolution and evolution rates. These lessons are just a portion of our high school biology course materials.

Evolution Overview - Chapter Summary and Learning Objectives

Follow along as professional instructors lead discussions on evolutionary theory and the evidence for evolution. Find out who Hardy and Weinberg were and how their equation is critical to the study of evolution. You'll be introduced to three types of speciation and natural and artificial selection. At the end of this chapter, you'll be familiar with:

  • Hypotheses on the rates of evolution
  • Adaptation
  • Pre- and post-zygotic barriers
  • Random mutation
  • Types of natural selection

Video Objective
Theory of Evolution Define population genetics and evolution. Learn about the theory of acquired characteristics, or the Lamarckian Inheritance, and the three principles of Darwinian evolution. Compare Darwin's and Lamarck's theories.
Evidence for Evolution: Paleontology, Biogeography, Embryology, Comparative Anatomy, and Molecular Biology Find out how comparative anatomy, molecular biology and paleontology are used to support the theory of evolution. Define biogeography and embryology and learn about their importance in evolutionary study.
Rates of Evolution Find out how rates of evolution are calculated and what influences these rates. Get details on punctuated equilibrium and molecular clock hypotheses.
Hardy Weinberg Equilibrium I: Overview Discern the criteria needed to attain Hardy-Weinberg equilibrium. Find out why this equilibrium is important and how the equilibrium equation is used.
Hardy Weinberg Equilibrium II: The Equation See the equation in action with simple examples. Learn how to use the equation to determine genotypic frequency and find out what the variables in the equation stand for.
Hardy Weinberg Equilibrium III: Evolutionary Agents Learn how to use the equation to identify populations that aren't in equilibrium. Discuss non-random mating, natural selection, genetic drift, population bottleneck and the founder effect.
Natural Selection and Adaptation Get definitions for these terms and understand how evolutionary fitness works. Find out about homologous structures and analogous traits and determine when convergent evolution occurs.
Types of Natural Selection Study directional, disruptive and stabilizing selection. Learn about heterozygote advantage and a balanced polymorphism.
Speciation I: Allopatric and Sympatric Speciation Learn how one species is split into two or more new species. Learn about physical separation and how it relates to allopatric and sympatric speciation.
Speciation II: Prezygotic Barriers Get definitions for zygote and pre- and post-zygotic reproductive barriers. Examine spatial isolation and mechanical isolation and learn about gametic and behavioral isolation barriers.
Speciation III: Postzygotic Barriers Find out the three types of postzygotic barriers. See what happens in hybrid zygote abnormality, hybrid infertility and low hybrid viability.
Genetic Variability and Random Mutation Get definitions for these terms. Find out why these concepts are important and see examples.
The Peppered Moths and Evolution Learn how farmers use artificial selection to grow preferred crops.
Artificial Selection Find out different techniques for artificial selection. Learn how this process works for plants and animals.

14 Lessons in Chapter 18: Evolution Overview
Theories of Evolution: Lamarck vs. Darwin

1. Theories of Evolution: Lamarck vs. Darwin

We'll look at the interplay between population genetics and environment. Are traits individually acquired or do entire populations evolve? The flying hamsters and a few other notable experiments will provide the answers.

Evidence for Evolution: Paleontology, Biogeography, Embryology, Comparative Anatomy & Molecular Biology

2. Evidence for Evolution: Paleontology, Biogeography, Embryology, Comparative Anatomy & Molecular Biology

There is much support for the theory of evolution. This evidence comes from a variety of scientific fields and provides information that helps us trace changes in species over time. In this lesson, we'll look at this evidence and explore how it supports the theory of evolution.

Rates of Evolution: Punctuated Equilibrium & Molecular Clock Hypothesis

3. Rates of Evolution: Punctuated Equilibrium & Molecular Clock Hypothesis

In general, evolution is a very long process. But rates of evolution can be different for different organisms. In this video lesson, you will identify how scientists study rates of evolution and fill in some of the missing 'steps' in the fossil record.

Hardy Weinberg Equilibrium I: Overview

4. 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.

Hardy Weinberg Equilibrium II: The Equation

5. 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.

Hardy Weinberg Equilibrium III: Evolutionary Agents

6. 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.

Natural Selection & Adaptation: Definition, Theory & Examples

7. Natural Selection & Adaptation: Definition, Theory & Examples

How does natural selection help shape the amazing types of animals we witness around us? In this lesson, we'll explore adaptations and what they can tell us about a species' past evolution.

Natural Selection: Definition, Types & Examples

8. 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.

Speciation: Allopatric and Sympatric Speciation

9. Speciation: Allopatric and Sympatric Speciation

Discover the definition of a species and learn more about how species split. Find out common terms related to the splitting of species and study what role polyploidy plays in the development of a species.

Prezygotic Reproductive Barriers & Speciation: Definition & Examples

10. Prezygotic Reproductive Barriers & Speciation: Definition & Examples

We may take for granted why animals choose to mate with other animals of similar appearance, but it's not that simple. There are actually biological barriers to reproduction that can prevent even seemingly closely related species from reproducing. This lesson looks at one such category of hindrances, prezygotic barriers, which make fertilization impossible.

Postzygotic Reproductive Barriers: Definition & Examples

11. Postzygotic Reproductive Barriers: Definition & Examples

Do flying hamsters represent a separate species from your run-of-the-mill hamsters? We'll get to the bottom of this by performing crosses between the two hamster types. You'll explore postzygotic reproductive barriers and their possibly tragic consequences.

Genetic Variability and Random Mutation

12. Genetic Variability and Random Mutation

Evolution is driven by variation among populations. The amount of variability determines how well a population can adapt to environmental changes, while random mutations can provide new variations that help a population adapt to unexpected changes.

An Example of Rapid Adaptation: The Peppered Moths

13. An Example of Rapid Adaptation: The Peppered Moths

Normally, adaptations occur over thousands or millions of years. However, drastic changes in the environment can shorten the time period in which a change comes about. In such cases, we can learn a lot about the evolutionary process and how natural selection drives it forward.

Artificial Selection in Evolution

14. Artificial Selection in Evolution

Humans have been selectively breeding for desirable traits in plants and animals for a long time. This artificial selection allows for a lot of control in the breeding process but can also lead to unintended mutations within a population of organisms.

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