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18.4: Echinoderms and Invertebrate Chordates

Difficulty Level: At Grade Created by: CK-12
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Lesson 18.4: True or False

Name___________________ Class______________ Date________

Write true if the statement is true or false if the statement is false.

_____ 1. A lancelet belongs to the same phylum as a tunicate.

_____ 2. A sea cucumber belongs to the same phylum as a sea star (starfish).

_____ 3. While larval echinoderms have bilateral symmetry, adult echinoderms have radial symmetry.

_____ 4. Echinoderms live in either freshwater or ocean water.

_____ 5. Tube feet depend upon the echinoderm's water vascular system for their ability to attach to a surface.

_____ 6. Wastes are excreted and oxygen diffuses in through the tube feet of echinoderms.

_____ 7. Unlike annelids, echinoderms cannot regenerate a lost body part.

_____ 8. The fertilized embryo of echinoderms develops directly into an adult.

_____ 9. As a group, Echinoderms can obtain food by filter-feeding, scavenging, or preying on other organisms.

_____ 10. The phylum Chordata contains only animals with a backbone.

_____ 11. Chordates have an unsegmented body.

_____ 12. The hollow nerve cord of chordates is located along the dorsal (top) side of the organism.

_____ 13. Adult tunicates are sessile.

_____ 14. Adult lancelets are sessile.

_____ 15. Tunicates can be very brightly colored.

Lesson 18.4: Critical Reading

Name___________________ Class______________ Date________

Read these passages from the text and answer the questions that follow.

Characteristics of Chordates

Chordates have three embryonic cell layers. They also have a segmented body with a coelom and bilateral symmetry. Chordates have a complete digestive system and a closed circulatory system. Their nervous system is centralized. There are four additional traits that are unique to chordates. These four traits, shown in the diagram below, define the chordate phylum.

  • Post-anal tail: The tail is opposite the head and extends past the anus.
  • Dorsal hollow nerve cord: The nerve cord runs along the top, or dorsal, side of the animal. (In nonchordate animals, the nerve cord is solid and runs along the bottom).
  • Notochord: The notochord lies between the dorsal nerve cord and the digestive tract. It provides stiffness to counterbalance the pull of muscles.
  • Pharyngeal slits: Pharyngeal slits are located in the pharynx. This is the tube that joins the mouth to the digestive and respiratory tracts.

Body Plan of a Typical Chordate. The body plan of a chordate includes a post-anal tail, notochord, dorsal hollow nerve cord, and pharyngeal slits. (Image courtesy of CK-12 Foundation and under the Creative Commons license CC-BY-NC-SA 3.0.)


1. Name the embryonic cell layers of chordates.

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2. Briefly describe the digestive system, nervous system, and circulatory system of chordates.

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3. What is a post-anal tail?

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4. What is the function of the notochord described in the passage?

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5. Define pharynx.

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Lesson 18.4: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

  1. Which of the following organisms is not in the phylum Echinodermata?
    1. brittle star
    2. lancelet
    3. sea star
    4. sand dollar
  2. Larval echinoderms have __________ symmetry, and adult echinoderms have __________ symmetry.
    1. no, bilateral
    2. radial, radial
    3. bilateral, radial
    4. trilateral, bilateral
  3. The function of muscular contractions that force water into the tube feet is
    1. regeneration.
    2. allowing the echinoderm to float with ocean currents.
    3. digestion.
    4. to enable the echinoderm to attach to surfaces.
  4. Echinoderm reproduction typically is
    1. sexual reproduction by budding.
    2. sexual reproduction with internal fertilization.
    3. by regeneraton.
    4. sexual reproduction with external fertilization.
  5. The life cycle of an echinoderms typically contains a
    1. free-swimming larval phase.
    2. pupal phase.
    3. long-lasting haploid phase.
    4. all of the above
  6. Tunicates live
    1. in the desert.
    2. in shallow freshwater ponds.
    3. in shallow ocean water.
    4. at the bottom of deep freshwater ponds.
  7. Which of the following is not a defining characteristic of chordates?
    1. pharyngeal slits
    2. a dorsal hollow nerve cord
    3. a complete digestive system
    4. an open circulatory system
  8. In humans, pharyngeal slits are present in the embryo and develop into the __________ during maturation.
    1. eyes
    2. nose
    3. middle ear
    4. outer ear

Lesson 18.4: Vocabulary I

Name___________________ Class______________ Date________

Match the vocabulary word with the proper definition.


_____ 1. phylum containing vertebrates

_____ 2. subphylum containing sea stars

_____ 3. subphylum containing feather stars

_____ 4. subphylum containing brittle stars

_____ 5. subphylum containing sea urchins

_____ 6. subphylum containing sea cucumbers

_____ 7. phylum containing sea stars and sand dollars

_____ 8. chemical attractants

_____ 9. simple eyes

_____ 10. the ability to grow back lost body parts

_____ 11. common name is sea squirt; are invertebrate chordates; adults are sessile

_____ 12. group containing only about 25 species; live on the ocean floor; adults can swim


a. Asteroidea

b. Chordata

c. Crinodea

d. Echinodermata

e. Echinoidea

f. Holothuroidea

g. lancelet

h. ocelli

i. Ophiuroidea

j. pheromones

k. regeneration

l. tunicate

Lesson 18.4: Vocabulary II

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

1. The subphylum containing sea cucumbers is __________.

2. The subphylum containing feather stars is __________.

3. The subphylum containing sea stars is __________.

4. The subphylum containing brittle stars is __________.

5. The subphylum containing sea urchins is __________.

6. The phylum containing vertebrates is __________.

7. The phylum containing sea stars and sand dollars is __________.

8. The ability to grow back lost body parts is __________.

9. __________ are chemical attractants.

10. __________ are the simple eyes of some echinoderms.

11. Sea squirt is a common name for __________.

12. __________ are filter feeders with adults that swim, and belong to the phylum Chordata.

Lesson 18.4: Critical Writing

Name___________________ Class______________ Date________

Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.

Name a few examples of echinoderms. What do they all have in common?

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