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Annelids, Mollusks and Arthropods
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Announcements
•There will be a quiz next lab that covers materials from annelids and echinoderms.•Assignment for this lab include page77, 78,79, 80 and 81
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This lab.
•definitions•Mollusks•Annelids•Arthropods•Dissection of formaline-fixed earthworm and squid•Examination of Grasshoppers,Crayfish
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Phylogeny of protostome matazoans
Mollusks Annelides
Arthropods
Mantle
Veliger larva
Radula
Closed vascular systemTrochophore larva lost
Jointed appendage
Exoskeleton
Metamerism
Trochphore larvaschizocoelom
Protostome mode of developement
Assumed ancestral character:bilateral symmetry, mouth and anus
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Definitions * Protostome (Schizocoelomate): multicellular metazoans with a coelom formed by splitting in the mesoderm layer*Trochophore: ciliated larval stage*Metamerism: body segmentation. Coelom in each segment is separated from the other.Segmentation allow better control of body movement and function. *Serially homologous structures share a common origin through segmental duplication.
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Definitions*Mantle: skirt-like epidermal enlargement that surround the viscera and is responsible for synthesis of the shell* Radula: tongue-like structure formed by a belt of tissue covered with chitinous teeth.*Setae: chitinous bristles on each segment used for burrowing.*Jointed exoskeleton: hard chitinous plates separated by flexible membranes
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Annelids, Mollusks and Arthropods
* Grouped together b/c they evolved three shared derived characters1- Trochophore larva2- Schizocoelom3- protostome mode of development
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Mollusks * They evolved1- mantle2- veliger larva (certain type of trochophore)3- radula*They feed on algae using the radula and exchange gases using gills*The foot (ventral mass of muscle) is used for locomotion
Radula heart of a clam mantle
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MollusksThey include1-Polyplacophora (chitons) -no distinct head -8 shell plates -large foot2-Gastropoda (snails) -distinct head -spiral shell -U-shaped gut3-Bivalvia (clams, oysters) - two parts shell -filter feeders
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Mollusks4-Cephalopoda(octopus, squid) -adapted for free swimming (jet propulsion of water) -muscular mantle -foot modified into multiple arms (8 in case of octopus and 8+2 tentacles in squid) -horny parrot-like beak adapted for predation -squid eyes are analogous to vertebrate eyes - the pen is a chitineous structure homologous to the exoskeleton of the arthropods and anologous to the notochord of vertebrates
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Annelids
*they are -metameric scchizocoels -nerves, muscles, nephridial tubes and blood vessels are serially homologous -closed vascular system -appendages on each segment include parapodia and/or setae -well developed digestive system(crop,gizzard, stomach and intestine) -gas exchange through body surface
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Annelids
They include1-Polychaeta (marine fanworms)2-Oligochaeta(earthworms)3-Hirudinea(leeches) -lost setae and move by undulatory swimming - it has some therapeutic indications (venous congestion to areas with good arterial supply)
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Arthropods
* They are -metameric schizocoel -segmentation is less regular(fused or lost) -lost trochophore larval stage -modification of the appendages (sensing, collection of food, grinding food, defense, transfer of gametes or aeration -ancestral open vascular system -jointed exoskeleton -complex gas exchange organs -serially homologous appendages
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Arthropods* They include1-Chelicerata (spider, mites and ticks) -chelicerae -cephalothorax and abdomen2-Crustacea (lobsters, crayfish and crabs) -aquatic -2 pairs of antennae -use mandibles to crush food -gills -head, thorax and abdomen -biramous appendages
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Arthropods
3-Uniramia (insects) -unbranched appendages -mouth with pair mandible and two pairs of maxillae -pair of antennae -branching gas-filled tubes -head, thorax and abdomen
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What should I do
1- dissect formaline fixed earthworm2- dissect fresh squid3- clams and grasshoppers also available 4-demo (live earthworm, leeches, hissing roaches)5-Sonoran arthropod studies institute cart (bug cart)