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Ch. 28 – Simple Invertebrates

Ch. 28 – Simple Invertebrates. Section 28.1. Sponges. The Simplest Animals. Sponges were once classified as plants Asymmetrical Lack tissues and organs Cell recognition makes them animals. The Simplest Animals. Sponges belong to Phylum Porifera System of pores Ostia

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Ch. 28 – Simple Invertebrates

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  1. Ch. 28 – Simple Invertebrates

  2. Section 28.1 Sponges

  3. The Simplest Animals Sponges were once classified as plants Asymmetrical Lack tissues and organs Cell recognition makes them animals

  4. The Simplest Animals • Sponges belong to Phylum Porifera • System of pores • Ostia • Pores that let water into sponge • Oscula • Pores that let water exit • Larger than ostia • Sessile

  5. Sponge Skeletons • Prevent sponge body from collapsing on itself • Composed of spicules • Tiny needle composed of silica or calcium carbonate • Some sponges contain spongin • Flexible protein fiber

  6. Types of Sponges • 3 Types of Sponges Based on Their Skeleton • Calcareous • Spicules composed of calcium carbonate • Glass • Spicules made of silica • Demosponge • Spongin

  7. Reproduction • Can reproduce asexually • Regenerate when cut into pieces • Commonly reproduce by shedding fragments • Also reproduce sexually • Hermaphrodites

  8. Section 28.2 Cnidarians

  9. Phylum Cnidaria • Jellyfish • Sea anemone • Hydras • Corals

  10. 2 Body Forms • Medusa • Umbrella-shaped • Polyp • Tubelike • Both have radial symmetry • Cells arranged into tissues

  11. Cnidocytes • Characteristic specific to Cnidarians • Stinging cells found on tentacles • Nematocyst • Barbed harpoon within cnidocytes • Some contain deadly toxins

  12. Hydrozoans • Most primitive cnidarians • Life cycle contains polyp and medusa stages • Some found in freshwater • Hydra • Use basal disk to attach to objects • Marine Hydrozoans • More complex than freshwater forms • Form colonies • Reproduction • Sexual and asexual reproduction • Some species are hermaphrodites

  13. Scyphozoans True jellyfish Range in size from a few cm to several feet in diameter Medusas Reproduce sexually

  14. Anthozoans • Largest class of cnidarians • Polyps • Brightly colored sea anemones and corals • Tubelike body topped with tentacles • Reproduce sexually and asexually • Sea Anemones • Feed on fish that swim near their tentacles • Reproduce asexually by pulling self in half • Corals • Found in colonies • Stonelike outer skeleton of calcium carbonate • Only outer layer of coral is alive

  15. Section 28.3 Flatworms and Roundworms

  16. Flatworms • Largest group of acoelomate worms • Tissues organized into organs • Bilateral symmetry • Belong to phylum Platyhelminthes • Turbellaria • Cestoda • Trematoda

  17. Turbellaria • Most are marine flatworms • Freshwater flatworms • Planaria • Have ability to be cut in half and regenerate • Reproduction method

  18. Cestoda • Parasitic tapeworms • Attach themselves to the intestinal wall of host • Proglottids • String of rectangular body sections • May reach 40 ft. long • Commonly infect humans when they eat infected meat that is undercooked.

  19. Trematoda • Largest flatworm class • Parasitic worms called flukes • Endoparasites contain tegument preventing them from being digested by host • Suck body fluids from host using pharynx • Lake itch • Burrows under skin

  20. Roundworms Common canine parasites Members of phylum Nematoda Pseudocoelom Long, cylindrical bodies

  21. Roundworm Infection Trichinellaspiraliscommon roundworm that infects humans Causes trichinosis Commonly occurs due to eating undercooked pork

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