Biology Week 17 - Worms

Day 1 - 3 | Day 4 | | Lab 1 | Lab 2 | Quizstar

  • Worm
  • Platyhelminthes
  • Flatworm
  • Planarian
  • Fluke
  • seta
  • Tapeworm
  • Nematoda
  • Roundworm
  • Hookworm
  • Trichinella
  • Heartworm
  • pinworms
  • Annelida
  • Segmented worm
  • Acoelomate
  • Pseudocoelomate
  • Coelomate
  • cephalization

Flat, Round, and Segmented Worms

The term "worm" does not refer to a specific taxonomic group of animals.

click to find the answer to today's question Even though a single earthworm is hermaphroditic, producing both sperm and egg cells, it takes two earthworms to reproduce. Why?

The Phyla:


A comparison of "worms" should include:

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Lab #1link to a local webpage with useful information

Lab #2link to a local webpage with useful information

Type of body cavity (coelom):

  • Flatworms are acoelomate - they have three germ layers, but no coelom.
  • Roundworms are pseudocoelomate - they have a cavity that forms between the mesoderm and the endoderm.
  • Segmented worms are coelomate - they have a true coelom which forms within the mesoderm.

Type of nervous system:

Type of digestive system:

Type of reproduction: Earthworm cocoons.  The visible measurement units are millimeters.

Type of locomotion:

Day 4 - Worms

click to find the answer to today's question How many hearts does an earthworm have?

The diagram below will serve as a review of the earthworm dissection you have done in the lower grades. As in your dissection, the diagram shows an earthworm with the dorsal surface cut open to expose the internal organs. You will notice that the segments are numbered along the bottom of the drawing.


Test your knowledgelink to an Internet Websiteof simple animals.

Day 4 Assignment - Worms (Test Your Concept Understanding)

Use the earthworm dissection diagram to answer the following questions.

  1. What part of the nervous system is located in segment 3?
  2. How many "hearts" does an earthworm have?
  3. What parts of the digestive system are located between the following segments?
    1. 4 to 6
    2. 7 to 12
    3. 13 to 15
    4. 16 to 18
    5. begins at segment 19 and goes to the posterior end
  4. All animals have one of two types of circulatory systems. What type of circulatory system does an earthworm have?
  5. A single earthworm produces both sperm and eggs. Use information shown on the diagram to explain why one earthworm cannot produce offspring.
  6. Use this earthworm cross-section diagram link to a local picture to answer the following questions.
    1. How many cell layers thick is the epidermis of an earthworm?
    2. The circular muscles of an earthworm contract to squeeze inward. This increases pressure on the body fluids and stretches the worm. The longitudinal muscles contract to shorten the earthworm. Movement of the worm is accomplished by the combination of these two muscle contraction. From information provided on the drawing, which set of muscles do you think is strongest, and why?
    3. How many pairs of seta are found on each body segment of the earthworm?
    4. The nerve cord and the majority of other body nerves are located along the ventral part of the earthworm body. What advantage does this serve?
  7. Watch this video on worms and answer the following questions.
    1. What phyla do the flat worms belong to?
    2. What phyla do the round worms belong to?
    3. What phyla do the segmented worms belong to?
    4. What type of digestive system is found in round worms?
    5. What type of animal is the first to possess a true heart?
    6. What are some ways humans can be infected with parisitic worms?

Research Links:

Biology Class










An earthworm's body is not structured in a way that allows it to bring its own sperm and egg cells together.










An earthworm has 5 "aortic arches" that function as hearts.