Lab 8 - Invert Anatomy - Student

Lab 8 - Invert Anatomy - Student - BSC2011 Lab 8...

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1 Two phyla (Mollusca and Arthropoda) encompass much of the morphological, ecological, and species diversity within the clade Bilateria (bilateral animals). Both phyla are protostome groups (mouth develops from the blastopore), but they have very different musculoskeletal and circulatory systems. Also, the Mollusca belong to the Lophotrochozoa, while the Arthropoda belong to the Ecdysozoa. Mollusca comes from the Latin molluscus meaning “soft”, which indicates that these organisms are soft- bodied creatures. Mollusks have a body plan made from 3 main body parts: a muscular foot for locomotion, a visceral mass containing most of the internal organs, and a mantle that covers the visceral mass and internal organs but is not enclosed within the visceral mass. Most mantles also typically secrete a shell. Today we will examine the squid, an organism from the Class Cephalopoda. The muscular foot has been modified in cephalopods into a muscular excurrent siphon, which they use for locomotion, as well as parts of the tentacles and head. A mantle covers the internal organs of cephalopods, but the shell has been reduced and internalized in the squid. Arthropoda comes from the Greek arthropod meaning “jointed feet”, which refers to the segmentation and jointed appendages of this group. Another prominent feature of arthropods is their hard exoskeleton. Today’s lab will examine the crayfish, an organism from the Class Crustacea. Crustaceans are known for their serially homologous, biramous (branched) appendages that have been extensively modified to perform specialized tasks. Crustaceans also are the only arthropods with 2 pairs of antennae. Objectives Identify major external and internal anatomical features of a cephalopod and a crustacean Understand the function of major tissues, organs, and systems Understand the concepts of homologous structures and serial homology BSC2011 Lab 8 Invertebrate Anatomy
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BSC 2011 Lab 8 Invertebrate Anatomy 2 Materials Dissecting tools Specimens : Squid Crayfish Squid ( Loligo sp. ) External Anatomy Place the squid dorsal side up (the gladius should be on the bottom) in the dissecting pan. Identify each structure of the squid’s external anatomy: arms , two longer feeding tentacles , head , eyes , fins , mantle , excurrent siphon (funnel), tail , suckers , beak , and mouth . How do the placement of the arm and tentacle suckers differ? Why does this difference occur? How does the squid use its funnel, mantle and fins for locomotion? Match each structure of the squid’s external anatomy with the appropriate letter. Eye _____ Tentacle _____ Feeding Tentacle _____ Excurrent siphon (funnel) _____ Mantle _____ Tail _____ Fins _____ A B C E F G D
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BSC 2011 Lab 8 Invertebrate Anatomy 3 Internal Anatomy Observe the mouth of the squid by opening and closing the beak. With tweezers, locate the small chitinous radula between the beaks and remove it. What is the radula’s function? The gladius and cranium comprise the squid’s skeleton. The
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Lab 8 - Invert Anatomy - Student - BSC2011 Lab 8...

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