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 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

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)

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

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

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

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)

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

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

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 atch?v=fBkmzzAh8Eo&feat ure=related atch?v=fBkmzzAh8Eo&feat ure=related

Phylum Platyhelminthes (flatworms) 3 tissue layers, acoelomate, incomplete GI tract Class Turbellaria (free living) Simple brain, branched GI, shared mouth/anus =E9E E2F9C9&playnext=1&index=10 =E9E E2F9C9&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

Tapeworm

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) 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

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

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)(leeches) Blood-sucking, releases an anesthetic and anticoagulant Consume 10X’s weight, can go months w/o another meal Medicinal uses

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

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

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

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

Phylum Echinodermata E.g sea stars, sand dollars, sea urchin and sea cucumbersea 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

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

Phylogeny Review