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Lecture 181. Describe the key features of Arthropods that promoted their diversity and characterize the major groups2. Review and describe the features of Deuterostomes3. Describe the ket characterisstics of Echinoderms4. Identify the characteristics that define all chrodates5. 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 Allows them to get minerals and water- Water can evaporate quickly so organisms are restricted to water Wormlke  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- Vulnerable when shedding/molting Tagma (tagmata) Head, thorax, abdomen- 3 segments Cephalathorax - 2 segments, head and thorax Fused segments 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 Spiracles lead into trachea, branch into tracheoles, go into air capillaries Malpighian tubues Excretion  Branch off of gut 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 - Blood doesn’t clot when feeding Mosquitos  Sap suckers Aphid on plant Claws  Arthropods are arranged into four classes Chelicerata (spiders, ticks, horshoe crabs) (scorpions, mites) Chelicerae- Mouth parts- Modified to manipulate food Two tagmata- Abdomen and cephalathorax  Pedipalps- For food manipulation Book lungs- 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- 3 pairs usually Terrestrial Wings- Some can be wingless Metamorphosis- Some have direct development Deuterestomes are triploblastic and coelomate Internal skeleton Skeleton can be composed of different things 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 Calcareous plates Strong Thin layer of skin covers ossicles Spines Not part of


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Ole Miss BISC 162 - Lecture notes

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