Lecture 18 1 Describe the key features of Arthropods that promoted their diversity and characterize the major groups 2 Review and describe the features of Deuterostomes 3 Describe the ket characterisstics of Echinoderms 4 5 Identify the characteristics that define all chrodates Identify Ecdysozoans must shed an external cuticle Molting 500 mya Paleozoic Exoskeleton external cuticle Chitin Cuticle used for protection and support Secreted by epidermis Priapulids Kinorhynchs Loriciferans have few species and are marine Thin cuticle Using for gas exchange Wormlke Allows them to get minerals and water Water can evaporate quickly so organisms are restricted to water Horsehair worms are parasites of arthropods Adult No mouth non functional gut Unsegmented Can be up to a meter long Found in freshwater terrestrial and aquatic organisms Nematodes are bilaterally symmetrical unsegmented roundworms Extremely abundant Most abundant and universally distributed animal group Free living parasitic predatory Pseudocoelomate Fluid in between ectoderm endoderm mesoderm Helps with movement Dorsal nerve cord Have a thick multilayered cuticle Exchange nutrients and oxygen using pharynx Some nematodes are parasitic Hook worm Pin worms Trichina worms Ascaris lumbrioides Separate sexes Elephantatiasis Nematode gets trapped in lymph node Tardigrades and onychophorans have fleshy appendages without joints Water bears been to space Can lay dormant for 10 years Hydrostatic skeleton Extremely small Lack a circulatory system and gas exchange organs Approximately 800 living species Found in marine water water films on plants Velvet worms Vicious predators Trap prey in sticky substance they secrete Live in humid tropical environments Have a thin flexible cuticle Have a fluid filled body Can act as a hydrostatic skeleton Internal fertilization Fertilized eggs carried around by female Arthropods are ecdysozoans Exoskeleton molting paired appendages Jointed appendages Arthropods are the most diverse group of animals Arthropods have rigid exoskeletons and jointed appendages Exoskeleton Composed of chitin Used for muscle attachment Must molt in order to grow Tagma tagmata Head thorax abdomen 3 segments Vulnerable when shedding molting Cephalathorax Fused segments 2 segments head and thorax Appendages with different function Different kinds of movement Walking swimming jumping gathering food Segmentation allows for modification Body is not a true coelom Hemocoel Inside of body chamber Open circulatory system where they pump fluid around There are several arthropod body plans Exoskeleton Helped them move onto lab Tagma tagmata Cephalathorax Jointed appendages Help with movement Barnacle Sit on their head Bring food into mouth with legs Pill bug roly poly Trilobites extinct represent the simplest arthropod body plan Cambrian ordivician Permian extinction ended Paleozoic One of the most common fossils from this region Marine organisms About 10 000 species Heavy exoskeleton Segmentation Appendages with different functions Many arthropods are adapted to live on land Exoskeleton Trachea Gas exchange Malpighian tubues Excretion Branch off of gut Spiracles lead into trachea branch into tracheoles go into air capillaries Arthropods are not limited to terrestrial habitats Marine freshwater Gills Swimming appendages Barnacle shrimp lobster crab Arthropods have complex organ systems Open circulatory system Use hemocoel and hemolymph Fountain like Circulatory not connected with respiratory Trachea Nitrogenous wastes Use malpighian tubules Secrete uric acid Arthropods have diverse feeding mechanisms Specialized mouth parts Pollen feeding Collecting nectar Fangs Filter feed with legs barnacles Blood suckers Anticoagulant Mosquitos Sap suckers Aphid on plant Claws Blood doesn t clot when feeding Arthropods are arranged into four classes Chelicerata spiders ticks horshoe crabs scorpions mites Chelicerae Mouth parts Modified to manipulate food Two tagmata Pedipalps Book lungs For food manipulation Abdomen and cephalathorax Looks like an accordion in chest Increased surface area Myriapoda centipedes millipedes Head and trunk 1 2 pairs of legs per segment Many repeated segments Centipedes Predators Can have venom Fast Millipedes Detritivores Slow Arthropods are arranged into four classes Crustacean crab lobster pill bug barnacles Three tagmata most Lobsters only have 2 Many appendages Feeding swimming gas exchange Legs on abdomen and thorax Gills Except pill bugs Arthropods are arranged into four classes Hexapoda insects Three tagmata Legs on thorax Terrestrial 3 pairs usually Wings Some can be wingless Metamorphosis Some have direct development Deuterestomes are triploblastic and coelomate Skeleton can be composed of different things Internal skeleton Earliest fossil was 520 mya Paleozoic All have bilateral symmetry and some point in life Radial cleavage Mouth second All have a complete gut Pharyngeal gills All organisms have at some point in development Echinoderms and Hemichordates are called ambulacrarians Larvae bilateral symmetry Echinoderms are deuterostomes Sea stars sea urchins feather stars sea cucumbers brittle stars Adult Echinoderms are pentaradially symmetrical Larvae bilateral symmetry Go through metamorphosis Cilia For movement Echinoderms have organ systems Water vascular system Unique to echinoderms Madreporite Pore on top Brings water in Tube feet Ring structure then moves down arms and terminates in tube feet Can use tube feet to walk or manipulate food Digestive system Digestive and reproductive structures down both arms Push stomach out of mouth secrete enzymes digest food suck stomach back into body Echinoderms have an endoskeleton Ossicles Spines Calcareous plates Strong Thin layer of skin covers ossicles Not part of endoskeleton Echinoderms have a diversity of feeding modes Predators Filter feeders Grazers Chordates are triploblastic coelomate bilaterally symmetrical deuterostomes Notochord dorsal hollow nerve cord post anal tail There are three key features of chordates Dorsal hollow nerve cord Becomes spinal cord and brain Post anal tail Notochord Flexible Becomes cartilage between vertebra Can be a supporting rod Pharyngeal gill slits Mostly embryonic Cephalochordates and Urochordates are usually sessile as adults Filter feeders The vertebrate notochord is replaced by a vertebral column Hagfish does not have vertebrae Hagfish and lampreys are early jawless vertebrates Scavengers predators Defense mechanisms