EEB 109 Week 2 Lab Manual

EEB 109 Week 2 Lab Manual - EEB 109 LAB INTRODUCTION TO...

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EEB 109 LAB INTRODUCTION TO MARINE SCIENCE Summer 2007 INVERTEBRATES I Introduction We will not have time to cover in the laboratory each phylum of animals with representatives living in the sea. Our approach will be to familiarize you with the dominant groups likely encountered on field trips. Today, you will be investigating the sponges (Phylum Porifera), jelly-bellies (Phylum Cnidaria) and segmented worms (Phylum Annelida). In addition, you will be introduced to the Phylum Ctenophora and the Phylum Bryozoa. The Sponges Although the sponges share some characteristics with the Metazoa, the closeness of the evolutionary ties between the two is questionable. Sponge cells are more highly organized than those of colonial protozoans, and their processes of gamete formation resemble those of metazoans. Nevertheless, the ability to regenerate a whole organism from its cellular parts and a pore-riddled body structure leads most marine scientists to conclude that sponges arose independently and that they represent an evolutionary dead end. Regardless of their evolutionary affinities, sponges are considered to be the simplest multicellular organisms. Any student who has tried to piece together a sponge’s structure with the aid of microscope slides could, however, quickly argue that their arrangements of cells, flagellated chambers, spicules and spaces are anything but simple. The basic body construction consists of an inner and outer layer of cells. Between the two cell layers lies a region called the mesohyl , which may be thick or thin. It contains the skeletal elements, the spicules (made of calcium carbonate or silicon dioxide) and spongin fibers (made of protein), as well as wandering cells of several types collectively called amoebocytes . The inner layer is made up of cells called choanocytes (collar cells), which filter the water and capture tiny food particles from suspension. Exercise: 1) Basic sponge anatomy and water circulation The sponge body is always covered on the outside with a series of two sizes of pores, or holes (Fig. 1). The smaller and more numerous pores are called ostia. These ostia, which are microscopic in most sponges, are always the place where water enters the sponge. The larger openings on the sponge body are called oscula . They function as excurrent openings for water leaving the sponge body. a. Place a live sponge under a dissecting microscope and see if you can find the ostia and oscula. 31
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b. Shine a bright light on the sponge and see if it contracts the ostia or oscula. Many sponges are sensitive to environmental cues, including chemicals, light, and mechanical stimuli. 2) Diversity As they develop and grow, sponges are notorious for changing morphology in response to environmental conditions. These animals are especially sensitive to forces imposed by ocean currents and by wind-generated waves. a.
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This note was uploaded on 03/05/2008 for the course EE BIOL 109 taught by Professor Cassano during the Winter '08 term at UCLA.

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EEB 109 Week 2 Lab Manual - EEB 109 LAB INTRODUCTION TO...

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