23 5 Roundworms KEY CONCEPT Roundworms have bilateral
23. 5 Roundworms KEY CONCEPT Roundworms have bilateral symmetry and shed their outer skeleton to grow.
23. 5 Roundworms Phylum: Nematoda • Unsegmented bodies • May be parasitic or nonparasitic • Inhabits a broad range of environments
23. 5 Roundworms shed their stiff outer skeleton as they grow. • Roundworms are protostomes with bilateral symmetry. pharynx brain intestine cuticle anus tail
23. 5 Roundworms • 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.
23. 5 Roundworms Many roundworms are parasites. • Nearly every plant and animal species are parasitized by roundworms. – hookworms – pinworms – Guinea worms
23. 5 Roundworms Hookworms • Contracted when walking barefoot in contaminated soil or sand • Inhabits the intestines of humans and other animals
23. 5 Roundworms Pinworms • Contracted by unintentionally ingesting eggs • Infest the intestines of humans and lay eggs around the anus
23. 5 Roundworms Guinea Worms • Contracted from drinking contaminated water from ponds or shallow open wells • Migrates under the skin and emerges through the feet
23. 5 Roundworms “The Worms” Webquest
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