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Animals with bilateral symmetry, 3 germ layers, organ systems and distinct heads.

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Immortal Worms
Teacher Contributed

Immortal Worms

Gold-Dotted Flatworm, Thysanozoon sp.

That Ain't A Worm!

Flatworms are amazing creatures. What's a flatworm? Well, it's not a worm, but it is flat. It's flat because these creatures have figured out how to breath without lungs or gills! They skin breathe, which means they actually exchange gases (O2 in, CO2 out) by diffusion through their skin. Pretty slick, no need to develop fancy structures that are easily damaged like alveoli or gill rakers. The skin is good enough for a flatworm. Diffusion is also the basic process we use to exchange our gases, the thing is it only works for a short distance, and we're big (at least in gas diffusion terms). This is why we have so many alveoli in our lungs, it allows us to bring all our blood to within a few cell widths of our air spaces. Once this happens, oxygen diffuses in and carbon dioxide diffuses out. This is also why flatworms are flat, if they were thicker or rounder they'd have to develop another way to breath like we did, because some of their cells would be too far away from the air or water to breath through diffusion. But if you don't need to be big, skin breathing is a pretty smart way to go. Watch these videos to find out even more about these intriguing creatures and why scientists are studying them.

Extension Investigation

Use the resources below to answer the following questions:

  1. How does Dr. Aboobaker hope to apply his work to human health?
  2. What are stem cells? What percentage of a flatworm's cells appear to be stem cells? How does this make them very resilient creatures?
  3. The smed-prep gene was identified as crucial for flatworms to regenerate their heads. What other organisms have been found to have this gene? What has this gene been shown to do in these organisms?
  4. What can flatworms do when food is scarce that other animals can't? What characteristic of flatworms let's them engage in this behavior?


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