Platyhelminthes: Definition, Characteristics & Examples

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  • 0:00 Platyhelminthes: A Big…
  • 0:35 General…
  • 1:24 Examples of Platyhelminthes
  • 2:53 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.

What is Platyhelminthes? In this lesson, you will learn about this phylum as well as some interesting interesting characteristics of Platyhelminthes organisms. You can read about some example organisms before taking a brief quiz.

Platyhelminthes: A Big Word for Flatworms

Let's say you're on a trip at the nature center. As you and your friends explore, you come across a big tank with many ocean organisms inside. You see what looks like a colorful piece of paper moving along slowly at the bottom of the tank. 'What is that?' You ask your guide Marlon.

Marlon tells you that the creature is a flatworm, a member of the phylum Platyhelminthes. 'Wow,' You say. 'What a weird looking animal!' Marlon goes on to explain that this little guy and his relatives are the stars of a new exhibit dedicated to the phylum as he leads you through your exploration of the Platyhelminthes exhibit.

General Characteristics of Platyhelminthes

Platyhelminthes is a very interesting phylum that contains nearly 20,000 species. These organisms are generally hermaphrodites, meaning they can have both male and female sexual organs and can produce offspring on their own. They're also soft-bodied invertebrates (they have no spine), and much like humans, flatworms have bilateral symmetry, which means that if you drew a vertical line down the middle of the animal, the left side of the organism would mirror the right side.

Most flatworms also do not have a body cavity! This means most flatworms really don't have anything inside but a small gut, and some don't even have that. They have a small opening through which they take in food and use the same opening to expel waste. Lastly, Platyhelminthes species range in size from microscopic to a few feet long, and they breathe across the whole body!

Examples of Platyhelminthes

As you go deeper into the nature center's Platyhelminthes exhibit, you see four different areas, each dedicated to the four classes of flatworms:

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