Transcript Chapter 29
Introduction to Invertebrates Chapter 29 Mader: Biology 8th Ed. Outline • • • • Evolution of Animals Sponges Cnidarians and Comb Jellies – Hydra – Obelia Bilateral Symmetry – Flatworms – Roundworms Mader: Biology 8th Ed. Evolution of Animals • • All animals are multicellular heterotrophic organisms that must take in preformed food. Classification Criteria – Level of organization Cellular, tissue, organ – Body Plan Sac, tube-within-a-tube – Segmentation Segmentation leads to specialization. Mader: Biology 8th Ed. Evolution of Animals – – Symmetry Radial - Two identical halves. Bilateral - Definite right and left halves. Type of Coelom Pseudocoelom Coelom Protostome - First embryonic opening becomes the mouth. Dueterostome - Second embryonic opening becomes the mouth. Mader: Biology 8th Ed. Multicellularity • Sponges – Only level of animal to have cellular organization. – Saclike bodies perforated by many pores. – Beating of flagella produces water currents that flow through pores into central cavity and out osculum. – Sessile filter feeders. – Asexual reproduction by fragmentation or budding. Mader: Biology 8th Ed. Simple Sponge Anatomy Mader: Biology 8th Ed. True Tissue Layers • • Total of three possible germ layers. – Ectoderm, endoderm, and mesoderm Animals in phlyum Ctenophora (comb jellies) and in phylum Cnidaria (cnidarians) develop only ectoderm and endoderm. – Diploblasts Radially symmetrical Mader: Biology 8th Ed. Cnidarian and Comb Jelly Mader: Biology 8th Ed. Comb Jellies • • • • Small, transparent, and often luminescent. Most of body composed of mesoglea. Largest animals propelled by beating of cilia. Capture prey with tentacles. Mader: Biology 8th Ed. Cnidarians • Tubular animals that most often reside in shallow marine waters. – Polyp and medusa body forms. – Specialized stinging cells (cnidocytes). Fluid-filled capsule, nematocyst. – Two-layered body sac. Outer layer - Protective epidermis. Inner layer - Gastrovascular cavity. – Nerve net found throughout body. Mader: Biology 8th Ed. Cnidarian Diversity Mader: Biology 8th Ed. Hydra • Freshwater cnidarians. – Small tubular poly body about one-quarter inch in length. Gastrovascular cavity is central cavity. – Tentacles can respond to stimuli. – Can reproduce sexually and asexually. Mader: Biology 8th Ed. Hydra Mader: Biology 8th Ed. Obelia • • A colony of polyps enclosed by a hard, chitinous covering. – Feeding polyps Extend beyond covering Have nematocyst-bearing tentacles. – Reproductive polyps Budding of new polyps. Also has sexual reproduction (medusae) stage. Mader: Biology 8th Ed. Obelia Mader: Biology 8th Ed. Bilateral Symmetry • • Ribbon worms (phylum Nemertea) – Have distinctive proboscis Flatworms (phylum Platyhelminthes) – Majority are parasitic – Organ-level organization No specialized circulatory or respiratory structures. – Have undergone cephalization – Ladder-type nervous system Mader: Biology 8th Ed. Free-living Flatworms • Planarians (genus Dugesia) – Live in freshwater habitats. – Head is bluntly arrow shaped. Auricles function as sense organs. Two light-sensitive eye spots. – Three kinds of muscle layers: Outer circular layer Inner longitudinal layer Diagonal layer Mader: Biology 8th Ed. Planarians – – – Excretory organ functions in osmotic regulation and water excretion. Can reproduce asexually Hermaphroditic Practice cross-fertilization Mader: Biology 8th Ed. Mader: Biology 8th Ed. Parasitic Flatworms • • Parasitic flatworms are flukes (trematodes) and tapeworms (cestodes). – Well-developed nerves and gastrovascular cavity are unnecessary. Flukes – Usually named for type of vertebrate organ they inhabit. Reproductive system well developed. Usually hermaphroditic. Mader: Biology 8th Ed. Transmission of Schistosomiasis Mader: Biology 8th Ed. Parasitic Flatworms • Tapeworms – Have anterior region with modifications for attachment to intestinal wall of host. Behind head region, scolex, a long series of proglottids are found. Segments each containing a full set of both male and female sex organs. – Complicated life cycles. Mader: Biology 8th Ed. Life Cycle of Taenia Mader: Biology 8th Ed. Pseudocoelom • • Pseudocoelom is a false body cavity that is incompletely lined by mesoderm. – Provides a space for internal organs and can serve as hydrostatic skeleton. Roundworms (phylum Nematoda) – Nonsegmented, generally colorless worms. – Several parasitic roundworms infect humans. Mader: Biology 8th Ed. Roundworm Anatomy Mader: Biology 8th Ed. Parasitic Roundworms • • • • Ascaris Trachinella - Trichinosis Dirofilaria - Heartworms Wuchereria - Elephantiasis Mader: Biology 8th Ed. Rotifers • Rotifers (phylum Rotifera) – Named for crown of cilia resembling a rotating wheel. Serves as both as an organ of locomotion and aids direction of food to mouth. Mader: Biology 8th Ed. Rotifer Mader: Biology 8th Ed. Review • • • • Evolution of Animals Sponges Cnidarians and Comb Jellies – Hydra – Obelia Bilateral Symmetry – Flatworms – Roundworms Mader: Biology 8th Ed. Mader: Biology 8th Ed.