Chapter 33 Invertebrates no back bone diploblastic 2 tissue layers EX cnidarian and ctenophore triploblastic 3 tissue layers ectoderm germ layer covering the outermost surface of the embryo and gives rise to the outer covering of the animal endoderm the innermost germ layer which lines the pouch that forms during gastrulation and gives rise to the lining of the digestive tract mesoderm third tissue layer which fills much of the space between the ectoderm and the endoderm Sponges basal animals that lack true tissues live in fresh and marine water habitats organized at the cellular level asymmetrical body no fixed shape sponges are suspension feeders filter water passing through their bodies chanoocytes line the spongocoel movement of flagella sets up water flow chanocytes trap food and ingest it by phagocytosis pass it along to amebocytes amebocytes transport nutrients to other cells secretes spicules pores doughnut shaped cells that span the body wall Water movement through a sponge would follow what path pore spongocoel osculum Concept 33 2 Cnidarians are an ancient phylum of eumtazoans Cnidarians a wide range of sessile and floating forms including jellyfish corals and hydras simple diploblastic radial body plan body plan is a sac with a central gastrovascular cavity single opening serves as both mouth and anus mesoglea layer is between epidermis and endodermis gastrodermis asymmetrical symmetry radial symmetry a slice through the central axis divides the animal into mirror images no distinct left right front back sides bilateral symmetry only one imaginary cut divides the animal into mirror images distinct left and right sides animals with bilateral symmetry are also said to be triploblastic Cnidarian Body Plan polyp form is generally sessile medusa form moves freely in water by passive drifting and contractions of the bell some cnidarians will switch between the two forms and some will stay one form forever Defining feature of cnidarians cnidocytes unique cells that function in defense and the capture of prey stimulus causes the cell to evert releasing thread some cnidocytes sting others just entangle prey Cnidarian Diversity hydrozoa group together scyphozoans cubozoans toxic anthozoans alternate between polyp and medusa when in the polyp stage they are colonial and basic jellyfish some alternate but other are only in the medusa form rectangular have specialized cells on the exterior that are called eye cells extremely mostly sessile no medusa stage at all many are colonial they can be very small or very large one mouth two tissue layers Which of the following animals is responsible for more lethal attacks on humans each year How many planes through the central axis will divide and organism with radial symmetry into roughly equal halves cubozoans many Concept 33 3 lophotrochozoans a clade identified by molecular data have the widest range of animal body forms bilateria show cephaliztion and 3 tissue layer coelomate an animal with a true coelom a true coelom form from tissue derived from the mesoderm a mesoderm that surrounds the endoderm and one that is against the other tissue layer as well they have an open body cavity have a body cavity completely lined by tissue derived from the mesoderm pseudocoelomate animals that have a body cavity that is formed from mesoderm and endoderm open body cavity mesoderm only touches the other tissue layer have a body cavity lined in part by tissue derive from the mesoderm but also by tissue derived from the endoderm acoelomate do not have an open body cavity but they still have the 3 tissue layers this is the most basic lack a bod cavity between the digestive cavity and the other body wall Flatworms phylum platyhelminthes triploblastic development but still acoelomates don t have gills because they exchange gas and wastes by diffusing them through their tissue layers live in marine water fresh water and terrestrial habitats flattened dorsoventrally between the dorsal and ventral surfaces 3 main groups turbellaria have light sensitive eye spots do not have a brain have centralized nerve net with anterior ganglia have gastrovascular cavity with 2 way pharynx only have one mouth trematoda parasitic live in the host body usually a vertebrate both male and female forms they will mate in your body eggs develop in a moist environment and then infect a secondary host snails tapeworms class cestoda scolex attaches to the host proglottids are the reproduce structures break off after fertilization do not have a mouth or gastrovascular cavity diffuse nutrients through their body anterior end is usually armed with suckers or hooks that the worm uses to attach itself to the intestinal lining of the host Rotifers phylum rotifera pseudocelomate reproduce by parthenogenesis they reproduce asexually eggs don t get fertilized but they still develop found in fresh water marine water and damp soil habitats multicellular with specialized organ systems alimentary canal a digestive tube tract with two openings mouth anus Sponge Bob is a member of which phylum Porifera In the life cycle of a typical hydrozoan which of the following would most likely be free swimming medusa Phylum Mollusca snails clams squids slugs and octupuses soft body protected by a hard shell marine land and freshwater animals all are soft bodied and secrete a hard protective shell made of calcium carbonate three main parts foot structure that helps them move main body called the visceral mass arteries and sinuses most mollusks have an open circulatory system the heart pumps hemolymph through mantle a fold on tissue that rapes over the visceral mass and secretes a calcium rich some have a radula strap like feeding organ scraps and scoops food items structure by commonly known as chitons oval shaped body and a hard shell that is segmented into 8 plates ONLY THE SHELL IS SEGMENTED NOT THE ACTUAL BODY foot used for locomotion shell the mouth Polyplacophora radula no true head Gastropods snails slugs found in marine freshwater and land habitats asymmetrical body usually with a coiled shell result of torsion rotation of the visceral mass foot for locomotion radula for feeding or defense torsion is a developmental process where part of the body twists up to 180 degrees moving the opening of the shell towards the front of the animal this is why they have spiraled shells Bivalvia clams mussels scallops oysters animals soft body head reduced or completely absent paired gills no radula because they
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