Sponges and Cnidarians
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C HAPTER
Chapter 1. Sponges and Cnidarians
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Sponges and Cnidarians
Key Concepts
• Structure and function of sponges
• Cnidarian adaptations, reproduction, and ecology
Standards
Lesson Objectives
• Describe the structure and function of sponges.
• Outline cnidarian adaptations, reproduction, and ecology.
Lesson Vocabulary
• bioluminescence: production of light by a living organism through biochemical means
• cnidarian: aquatic invertebrate such as a jellyfish or coral in Phylum Cnidaria
• coral: aquatic invertebrate in Phylum Cnidaria that lives in a large colony in shallow ocean water and may
build a reef
• coral reef: hard, mineralized underwater structure that is built by coral animals as an exoskeleton and provides
a habitat for many other ocean organisms
• endoskeleton: internal skeleton of cartilage and bone that supports and protects the body of vertebrates
• jellyfish: aquatic invertebrate in Phylum Cnidaria that lives virtually anywhere in the ocean and is typically a
predator
• medusa (medusae, plural): one of two cnidarian body forms (the other is the polyp), in which the animal is
bell shaped and typically able to move
• polyp: one of two cnidarian body forms (the other is the medusa), in which the animal is tubular and usually
attached to a surface and unable to move
• sponge: simple aquatic invertebrate in Phylum Porifera, which lives attached to surfaces and filters food from
the water
Teaching Strategies
Introducing the Lesson
Bring a dried sea sponge to class, and have students pass it around and examine it. Call on volunteers to describe
the sponge and explain what it is. If necessary, identify it as a marine sponge and say that it is the simplest type
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of animal. Challenge students identify any characteristics of the sponge that would lead them to classify it as an
animal. Conclude by telling students will learn about the sponge phylum in this lesson.
Demonstration
The URL below is a slide presentation on sponges and cnidarians. It includes basic information about each phylum and many colorful images of animals in each taxon. It is a good way to illustrate classroom discussions of
these phyla. https://docs.google.com/presentation/d/1bpD7zZZFipgFP3QI_2votVscUQ0-dvJSJbmV0JIZhQ8/pres
ent?slide=id.i0
Demonstration
Use the short video at the following URL to demonstrate to students how sponges filter water for food. http://www.y
outube.com/watch?v=T7E1rq7zHLc
Activity
Hand out copies of the sponge anatomy worksheet at the URL below, and have pairs of students work together to
label the structures. http://www.biologycorner.com/worksheets/sponge-anatomy.html
Differentiated Instruction
Assign less proficient readers the cnidarian article at the following URL. After they read the article, have them
complete the questions at the end, which require them to locate pertinent information in the reading. From the
assignment, they will learn about cnidarians and also improve their reading skills. http://www.biologycorner.com
/worksheets/articles/hydra.html
Enrichment
Challenge a few students to identify and explain to the class some of the many scientific inaccuracies about sponges
in the cartoon show “SpongeBob SquarePants.” Suggest that they watch this short video for a few ideas: http://w
ww.youtube.com/watch?v=NFy3gHWF5oo
Science Inquiry
At the first URL below, you can access a hydra microscope activity, which allows students to observe preserved and
living hydra. The second URL is a short video of a living hydra as viewed under a microscope that you can use
instead of living hydra on a slide. In the activity, students will observe and interpret hydra behavior. http://www.b
iologycorner.com/worksheets/hydra.html http://www.schooltube.com/video/8b4ca7db15144b83b7c6/Hydra
Overcoming Misconceptions
Misconceptions about jellyfish abound. One of the most common is that they are fish. Have students read the article
below to learn more about jellies and some of the misunderstandings about them. http://aquaviews.net/explore-the
-blue/truth-misunderstood-jellyfish/
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Chapter 1. Sponges and Cnidarians
Reinforce and Review
Lesson Worksheets
Copy and distribute the Lesson 12.1 worksheets in CK-12 MS Life Science Workbook. Ask students to complete
the worksheets alone or in pairs to reinforce lesson content.
Lesson Review Questions
Have students answer the Review Questions at the end of Lesson 12.1 in CK-12 MS Life Science Flexbook. Answers
are provided below.
1.
2.
3.
4.
Describe the ability of sponges and cnidarians to move.
Identify specialized cells in sponges, and state their functions.
What is a nematocyst? What is its role?
Besides cnidarians, many other ocean organisms are bioluminescent. What is bioluminescence? Why do you
think it is relatively common in ocean organisms such as cnidarians?
5. Compare and contrast the medusa and polyp forms of cnidarians, including how they reproduce.
6. Explain why coral reefs are found only in shallow water.
Lesson Quiz
Check students’ mastery of the lesson with Lesson 12.1 Quiz in CK-12 MS Life Science Assessments.
Points to Consider
Cnidarians such as jellyfish have radial symmetry. Flatworms and roundworms, which you will read about next,
have bilateral symmetry.
• What did flatworms and roundworms need to evolve first in order to develop bilateral symmetry?
• Why is bilateral symmetry adaptive?
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