Ch 23: Holt McDougal Biology Chapter 23: Invertebrate Diversity

About This Chapter

The Invertebrate Diversity chapter of this Holt McDougal Biology Companion Course helps students learn the essential lessons associated with invertebrate diversity. Each of these simple and fun video lessons is about five minutes long and is sequenced to align with the Invertebrate Diversity textbook chapter.

How It Works:

  • Identify the lessons in the Holt McDougal Invertebrate Diversity chapter with which you need help.
  • Find the corresponding video lessons with this companion course chapter.
  • Watch fun videos that cover the invertebrate diversity 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:

  • Characteristics that various animals have in common
  • Evolutionary history of animals
  • The definition of Parazoa
  • Characteristics of Radiata and protostomes
  • Types of flatworms and roundworms
  • Anatomy and reproduction of mollusks
  • Structure of annelids
  • Traits of echinoderms
  • Definition of deuterostomes

Holt McDougal is a registered trademark of Houghton Mifflin Harcourt, which is not affiliated with

12 Lessons in Chapter 23: Holt McDougal Biology Chapter 23: Invertebrate Diversity
Test your knowledge with a 30-question chapter practice test
Common Characteristics of Members of the Animal Kingdom

1. Common Characteristics of Members of the Animal Kingdom

From a bat to a sea anemone, the animal kingdom contains a diverse group of organisms. This lesson will outline the characteristics animals share and will explain why critters that seem so different are included in the same kingdom.

The Evolution of Animals: Importance & Evolutionary History

2. The Evolution of Animals: Importance & Evolutionary History

The animal kingdom ranges from simple organisms like sponges to complex organisms like humans. We will look at some defining characteristics of animals as well as examples of both invertebrates and vertebrates.

Animal Body Plans: Classifications and Features

3. Animal Body Plans: Classifications and Features

The Animal Kingdom is diverse and complex. How do we make sense of it all? Scientists use body plans to classify and organize the animals of Earth, making it much easier to differentiate between them.

Parazoa: Definition and Characteristics

4. Parazoa: Definition and Characteristics

The sub-kingdom Parazoa is a special group of animals that are unlike any other. In this video lesson, you'll learn about the characteristics of Parazoans and identify what makes them a unique section of the Animal Kingdom.

Cnidarians: Types & Examples

5. Cnidarians: Types & Examples

Corals and jellyfish belong to a group of invertebrate animals called Cnidarians. In this lesson, you will learn about the classification and biology of these fascinating organisms and their relatives, including one of the most lethal creatures known to mankind: the Australian box jellyfish.

Radiata: Definition and Characteristics

6. Radiata: Definition and Characteristics

The super-phylum Radiata describes a unique and interesting group of animals. In this video lesson you'll identify various animals that belong in this classification as well as describe the characteristics that make them so identifiable.

Protostomes: Definition and Characteristics

7. Protostomes: Definition and Characteristics

Though you may not be able to tell just by looking at them, protostomes are an evolutionarily related group based on shared characteristics of their body plans. In this lesson, you will identify these characteristics, as well as see examples of the variety of animals this group encompasses.

Flatworms: Types & Structure

8. Flatworms: Types & Structure

Flatworms belong to the phylum Platyhelminthes, which includes planarians, flukes, and tapeworms. Learn more about these animals as you explore the contents of this lesson.

Mollusks: Characteristics & Types

9. Mollusks: Characteristics & Types

Do you like to eat seafood, hunt for seashells, or learn about scary sea creatures? If so, then you'll want to learn about the different types of mollusks, which include the tasty bivalves, the cool-looking gastropods, and the weird cephalopods.

Annelids: Types & Structure

10. Annelids: Types & Structure

Annelids are worms with segmented bodies. Annelids are divided into three main classes. A brief description and example of each class will be provided in this lesson.

Echinoderms: Traits, Types & Roles

11. Echinoderms: Traits, Types & Roles

After watching this lesson, you'll be well on your way to being an echinoderm expert! For example, you'll learn that sea cucumbers help clean up the ocean floor and that starfish can grow back any arms that are broken or damaged.

Deuterostomes: Definition and Characteristics

12. Deuterostomes: Definition and Characteristics

Deuterostomes, like tunicates and urchins, are amazing creatures that are classified together because they share aspects of their evolutionary pasts. In this lesson, you'll identify these characteristics and see what makes this group of animals unique.

Chapter Practice Exam
Test your knowledge of this chapter with a 30 question practice chapter exam.
Not Taken
Practice Final Exam
Test your knowledge of the entire course with a 50 question practice final exam.
Not Taken

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Other Chapters

Other chapters within the Holt McDougal Biology: Online Textbook Help course