1. KEY CONCEPT Roundworms have bilateral symmetry and shed their outer skeleton to grow.

2. Phylum: Nematoda
Unsegmented bodies
May be parasitic or non-parasitic
Inhabits a broad range of environments

3. Roundworms shed their stiff outer skeleton as they grow.
brain
cuticle
pharynx
intestine
anus
tail
Roundworms are protostomes with bilateral symmetry.

4. Roundworms have a tough outer skeleton called a cuticle.
made of chitin
must be shed to grow
Roundworms have a pseudocoelom (fluid-filled body cavity), not completely lined by muscle.
Roundworms reproduce sexually.
chitin

5. Many roundworms are parasites.
Nearly every plant and animal species are parasitized by roundworms.
hookworms
pinworms
Guinea worms

6. Hookworms
Contracted when walking barefoot in contaminated soil or sand
Inhabits the intestines of humans and other animals

7. Pinworms
Contracted by unintentionally ingesting eggs
Infest the intestines of humans and lay eggs around the anus

8. Guinea Worms
Contracted from drinking contaminated water from ponds or shallow open wells
Migrates under the skin and emerges through the feet

9. “The Worms” Webquest