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Invertebrate Evolution

Invertebrate Evolution. Chapter 18. Defining Animals. Multicellular, heterotrophic eukaryotes that obtain nutrients by ingestion or eating food No cell walls for structure Joined by extracellular proteins and intercellular junctions

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Invertebrate Evolution

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  1. Invertebrate Evolution Chapter 18

  2. Defining Animals • Multicellular, heterotrophic eukaryotes that obtain nutrients by ingestion or eating food • No cell walls for structure • Joined by extracellular proteins and intercellular junctions • Most have muscle cells for movement and nerve cells for signal conduction • About 35 phyla in kingdom animalia; we examine 9 • All but 1 are invertebrates or lack a backbone

  3. Animal Life Cycles • Haploid gametes fuse into zygote • Mitosis forms a hollow ball of cells = blastula • Invagination produces a gastrula • Becomes GI system lined with endoderm • Ectoderm for outer covering, some nervous systems • Mesoderm for muscles and internal organs • Larva stage metamorphosis to adult (some animals)

  4. Constructing Phylogenetic Trees • Morphological similarities and differences in body plans • Symmetry • Tissue organization • Embryonic development • Body cavity is an additional body plan feature Kingdom Animalia

  5. Symmetry • Radial often sedentary • Bilateral (most) often mobile • Anterior and posterior • Ventral and dorsal • Location of brain, sense organs, and mouth

  6. Tissue Organization • True tissues are specialized cells, separated by layers • Absent in Porifera (level of organization?) • Formed during gastrulation • 2 layers is ecto- and endoderm • 3 layers is ecto-, meso-, and endoderm

  7. Body Cavity • A coelom or fluid filled space between GI tract and outer body wall • Allows organ movement, protection, and development • Presence or absence divides 3 tissue layer organisms • True coelom is completely lined with mesoderm • Pseudocoelom not completely lined • Platyhelminthes (flat worms) lacks (acoelomate)

  8. Embryonic Development • Based on gastrula opening formed • Protostomes: opening becomes mouth • E.g Arthropoda • Deuterostomes: opening becomes anus • Mouth forms elsewhere • E.g Chordates

  9. Phylum Porifera (Sponges) • Most are stationary (sessile), marine, and asymmetrical • Draws water in through pores and out an osculum • Suspension feeders • Choanocytes pull in food and water • Amoebocytes provide support • Spicules is mineralized material • Spongin is flexible protein • No muscles or nerves • Toxins and antibiotics release for protection

  10. Phylum Cnidaria (Cnidarians) • Radial symmetry and 2 tissue layers • Jelly like substance between • Contractile and nervous tissue (simple) • Exist as polyps or medusas • Carnivorous, use cnidocytes • Incomplete GI tract • http://www.youtube.com/watch?v=fBkmzzAh8Eo&feature=related

  11. Phylum Platyhelminthes (flatworms) • 3 tissue layers, acoelomate, incomplete GI tract • Class Turbellaria (free living) • Simple brain, branched GI, shared mouth/anus • http://www.youtube.com/watch?v=axBaCD4wYXE&feature=PlayList&p=E9E1093124E2F9C9&playnext=1&index=10 • Class Trematoda (flukes) • Animal parasites • Suckers to attach and interior all repro. organs • Larval intermediate stage • Class Cestoda (tapeworms) • Vertebrate GI tract parasites • Scolex, no mouth (absorption), hermaphrodite, eggs released from end in feces • Multiple hosts • http://www.youtube.com/watch?v=GMSc2RZ19Us

  12. Tapeworm

  13. Phylum Mulluska (Mollusks) • Coelomates, separate sexes, larval stage (trochophore), circulatory and advanced sensory systems • Muscular foot, visceral mass, mantle, radula (chitinous tongue) • Class Gastropoda (snails and slugs) • Live on land and in all waters • Class Cephalopoda (squids and octopuses) http://www.youtube.com/watch?v=9-azBDt0kik&feature=related • http://www.youtube.com/watch?v=5mBhKe4DxQ4 • Mouth at end of foot, shell small or absent • Most advanced invertebrate brain and sense organs (eyes) • Class Bivalva (scallops, oysters, and clams) • 2 shells hinged together • Suspension feeders, mantle has gills for food and gas exchange

  14. Phylum Nematoda (Roundworms) • Pseudocoelomate, GI tract with 2 openings, separate sexes, and lateral muscles • Free-living (C. elegans) • Parasitic • Dog heartworm • 50 species in humans • Trichinella spiralis • Hook worms • Pinworms

  15. Phylum Annelida (Segmented Worms) • Segmentation, longitudinal and circular muscles, closed circulatory system • Class Polychaeta • Marine organisms, live in tubes, can be colonial • Class Oligochaeta (earthworms) • Segmented excretory, circulatory, repro, and nervous systems; unsegmented GI tract • Hermaphroditic, thickened region gathers gametes and is left in soil • Class Hirudinea(leeches) • Blood-sucking, releases an anesthetic and anticoagulant • Consume 10X’s weight, can go months w/o another meal • Medicinal uses

  16. Phylum Arthropoda (Arthropods) • Most successful phylum • Exoskeleton • Protects and allows joint attachment • Protein and chitin that Is molted with growth • Segmentation • Head, thorax (fused is cephalothorax), and abdomen • Sensory, protection and walking, and swimming respectively • Open circulatory system, blood not contained in vessels • Aquatic species with gills, terrestrial with air sacs

  17. Subphylums • Chelicerates (arachnids) • Hollow mouth appendages • First terrestrial carnivores, deliver venom or toxins • E.g scorpions (night), spiders (day), and ticks/mites • Mandibulata • Solid mouth organs • Examples • Millipedes are herbivores with 2 leg sets per segment • Centipedes are carnivores with 1 leg set per segment • Lobsters, and insects

  18. Classes • Crustacea (Crustaceans) • Aquatic (mostly) and have gills (rolly-polly) • Include lobsters, crayfish, shrimp, barnacles, and crabs • Insecta (Insects) • Most diverse group • Wings, advanced sensory organs, communication, and social structure • Waterproof cuticle, short lives, complex life cycles, and large offspring broods

  19. Class Insecta • Life cycles • Only adults can reproduce or have functional wings • Multiple molts allow for metamorphosis, complete or incomplete • Food sources differ so enhances adaptability • Body plan • 3 parts: head, thorax, and abdomen • Embryonic segments develop independently • Connects with mutation and evolution • 3 pairs of legs, not at cost to legs • Coloration • Camouflage, mimicry, and coloration from independent development

  20. Phylum Echinodermata • E.g sea stars, sand dollars, sea urchin and sea cucumber • Radial symmetry internally and externally as an adult • Bilateral symmetry in larval stage • Calcium containing plates form endoskeleton • Tube feet that are extensions of a water vascular system • For locomotion, feeding, and gas exchange • Mouth and stomach adaptations • deuterostomes • Capable of regeneration

  21. Phylum Chordata • 4 characteristics • Dorsal, hollow nerve cords • Notocord between GI tract and nerve cord • Pharyngeal slits • Post-anal tail • Tunicates (Sea squirts) • Adult has pharyngeal slits only, larva has all four • Lancet • Suspension feeders • Mucus net to trap food

  22. Phylogeny Review

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