lab7_mollusca_2007

Lab7_mollusca_2007 - Laboratory 7 Mollusca 120 Laboratory 7 Mollusca OBJECTIVES After completing today's lab you will be able to 1 Compare and

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Mollusca Laboratory 7
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120 Laboratory 7: Mollusca OBJECTIVES After completing today’s lab you will be able to: 1. Compare and contrast molluscs with earthworms and flatworms with respect to: body plan support and movement respiration circulatory system feeding and digestion reproduction LAB PREPARATION In preparation for this laboratory you should do the following: 1. Read and study this laboratory. 2. Read Chapter 33, and re-read the invertebrate sections of Chapters 40, 41, 42, and 44 in Campbell (7 th Edition). 3. Bring your dissection instruments to lab. 4. Wear your lab coat and gloves for this lab. Most members of the Phylum Mollusca (L. molluscus, soft) are included in the four major classes: Polyplacophora (chitons), Gastropoda (slugs, snails, and limpets), Bivalvia (clams and related forms) or Cephalopoda (squid and octopods). There are four additional minor classes. In this lab, you will be focusing on clams. A. Body plan Molluscs are bilaterally symmetrical and are believed to have evolved from annelid-like ancestors. Although their mode of development is similar to annelids, molluscs completely lack segmentation and have greatly reduced the size of the coelom. The Phylum Mollusca is one of the most morphologically diverse animal groups. The adaptations that members of the different classes possess have allowed for their great success in many different environments. Despite this diversity, all molluscs are derived from a general body plan with three main body regions: a head-foot, a visceral mass, and a mantle. The primary functions of the head-foot region are locomotory and sensory. Atop the head-foot is the visceral mass that contains the digestive, circulatory, reproductive, and excretory organs. The mantle covers the visceral mass, assuming a variety of functions including secretion of the shell and respiration. In each of the four classes, these three body regions vary in their dominance. Bivalves are generally sedentary. The head has been completely suppressed, making it difficult sometimes for us to determine which way is up. The foot, visceral mass, and mantle dominate the body.
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Laboratory 7: Mollusca 121 The majority of bivalves are filter-feeders with large ctenidia (gills). The mantle encloses the entire body and is itself surrounded by a hinged shell that it secretes. Figure 7-1. Shell layers in Mollusca and how pearls are formed. Bivalves possess an exoskeleton, the shell. The shell is composed of three layers (see Figure 7-1). On the outside of the shell is a thin, proteinaceous covering called the periostracum. This covering is most clearly visible at the hinge. It is secreted by the inner edge of the mantle lobe. The middle layer, the prismatic layer, is composed of calcium carbonate. It is secreted by the tip of the mantles outer lobe. The innermost layer is the nacreous
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This note was uploaded on 04/10/2008 for the course BIO 172L taught by Professor Gerald during the Spring '08 term at Hawaii.

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Lab7_mollusca_2007 - Laboratory 7 Mollusca 120 Laboratory 7 Mollusca OBJECTIVES After completing today's lab you will be able to 1 Compare and

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