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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 endodermSponges•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 wallWater movement through a sponge would follow what path?•pore--> spongocoel --> osculumConcept 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•alternate between polyp and medusa, when in the polyp stage they are colonial and group together•scyphozoans•basic jellyfish, some alternate but other are only in the medusa form•cubozoans•rectangular, have specialized cells on the exterior that are called eye cells, extremely toxic•anthozoans•mostly sessile, no medusa stage at all, many are colonial, they can be very small or verylarge, one mouth, two tissue layers•Which of the following animals is responsible for more lethal attacks on humans each year?•cubozoansHow many planes through the central axis will divide and organism with radial symmetry into roughly equal halves?•manyConcept 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 aswell, 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 theystill 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?•PoriferaIn 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• most mollusks have an open circulatory system. the heart pumps hemolymph through arteries and sinuses• mantle-a fold on tissue that rapes over the visceral mass and secretes a calcium rich shell•some have a radula: strap-like feeding organ; scraps and scoops food items; structure by the mouth• Polyplacophora• 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• 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,


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LSU BIOL 1202 - Chapter 33: Invertebrates

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