Unit 8 Chapter 26 Sponges Cnidarians Flatworms and
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Unit 8 Chapter 26 Sponges, Cnidarians, Flatworms, and Roundworms
What is a Sponge? n n Phylum Porifera (“pore-bearing”) Sponges are aquatic, sessile, asymmetrical invertebrates
What is a Sponge? n n Sponges are filter-feeders Feed by filtering small particles from the water that passes through its pores
What is a Sponge? n n Sponges are softbodied and may contain sharp, hard spicules for support & defense Others may contain spongin, a soft, fibrous material
What is a Sponge? n n n Hermaphrodites, producing both eggs & sperm A few have external fertilization (occurring outside the animal’s body) Most have internal fertilization (eggs & sperm meet within the animal’s body)
What is a Cnidarian? n n Radially symmetrical, aquatic invertebrates Ex: Jellyfish, coral, hydra, & sea anemones
What is a Cnidarian? n n Cnidarian’s body is only two cell layers Cnidarian’s sting their prey with cells called nematocysts, located on their tentacles
What is a Cnidarian? n n n Cnidarian’s have two basic body shapes: Medusa = bell -shaped, freeswimming Polyp = tube -shaped, sessile
What is a Cnidarian? n n Many Cnidarians live in colonies Ex: Portuguese man-of-war Some Cnidarians build reefs Ex: Coral
What is a Flatworm? n n n Phylum Platyhelminthes Acoelomates, with three cell layers Marine, freshwater, & moist land habitats A Fluke
What is a Flatworm? n n Flatworms may be free-living, like the fresh-water Planarian Planaria have a simple nervous system, including eyespots for light detection
What is a Flatworm? n Planaria have remarkable powers of regeneration, the ability to replace missing parts
What is a Flatworm? n n Flatworms may be parasitic, like the fluke & tapeworm Tapeworms attach to host’s intestines with their scolex (head) and produce many proglottids (body segments)
What is a Flatworm? n Tapeworms have a complex life history, that may include several hosts
What is a Roundworm? n n n Phylum Nematoda Pseudocoelomates, with two body openings Free-living forms are important decomposers in the soil
What is a Roundworm? n n Many roundworms are parasites, i. e. pinworms, hookworms, & heartworms Trichinosis is a disease caused by a roundworm found in improperly cooked pork Heartworms in a Dog’s heart
