The Reproduction System of Platyhelminthes

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  • 0:00 Surprise Reproduction
  • 1:00 What Are Platyhelminthes?
  • 1:34 Reproduction
  • 3:16 Lesson Summary
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Lesson Transcript
Instructor: Ebony Potts

Ebony has taught middle and high school physical science, life science & biology. She's also been an assistant principal and has a doctorate in educational administration.

Have you ever heard of an organism from the phylum Platyhelminthes? Do you know how they reproduce? In this lesson you will learn the answers to these questions as well as some characteristics of Platyhelminthes and their relatives.

Surprise Reproduction

You are so excited to be working with Dr. Thomas, one of the best biologists on campus. Right now she is conducting experiments with organisms that she refers to as Platyhelminthes, or flatworms.

Dr. Thomas has some of them in small containers in the lab. She has charged you to watch one particular container, container C, that has one tan colored flatworm inside. The worm is in the container with all it needs for the next couple of days while Dr. Thomas is away, so it should be fine.

You leave the lab turn off the lights and lock up for the weekend. When you come back on Monday, you notice that container C now has multiple flatworms floating around inside. How is that possible? Were there two flatworms inside the whole time, and you didn't notice?

Dr. Thomas walks in, notices the panic on your face and laughs. She says, 'Oh good, we have some new offspring!' She offers you a seat and begins to explain flatworm reproduction to you.

What Are Platyhelminthes?

Flatworms are very unusual animals. Even though most people don't know much about this phylum, Platyhelminthes are very plentiful, with around 20,000 different types. One of the most famous is the tapeworm, which can parasitize many animals including dogs, cats, and humans.

The typical flatworm is a soft, flat invertebrate, meaning it has no backbone. It's also bilaterally symmetrical. Bilateral symmetry means that if a vertical line is placed in the middle of the organism, what is on the left side is mirrored on the right side.


Most flatworms are hermaphrodites, organisms that have both male and female sex organs. As a result of this characteristic, they are able to reproduce asexually and sexually.

Platyhelminthes have three methods by which they can reproduce:

  1. They can fertilize their own eggs
  2. They can regenerate a complete organism from a piece of themselves
  3. They can reproduce sexually with another flatworm

This is why the flatworm in container C was able to reproduce even though there was only one organism in the container.

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