biol_119__lecture_3__9-4-09

biol_119__lecture_3__9-4-09 - Lecture 3, September 9, 2009...

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Tutors are available in the ISC, Biology Learning Center, RM 139 and will begin on Tuesday, 9-8-09. Lecture 3, September 9, 2009 Biol 119 Sun. Mon. Tues. Wed. Thurs. Katie 6-8 Katie 6-8 Alex 6-8 Alex 4-6 Katie 7-8 Alex 6-7
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Lecture 3, Lots more invertebrates; now for ones with true muscle and nervous tissues. http://news.nationalgeographic.com/news/2006/01/0119_060119 _jellyfish.html
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Review question: Which statement is True? A. The coelom eventually forms the digestive tube running from mouth to anus. B. In deuterostomes, the blastopore becomes the mouth. C. Spiral cleavage is associated with determinate cleavage D. Sponges feed by photosynthesis E. None of the above, all are false
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Concept Check 33.1 How sponges feed? The flagella of choanocytes draw water through their collars, which trap food particles. The particles are engulfed by phagocytosis and degested, either by choanocytes or by amoebocytes.
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Concept 33.2: Cnidarians are an ancient phylum of eumetazoans All animals except sponges belong to the clade Eumetazoa, the animals with true tissues The phylum Cnidaria is one of the oldest groups in this clade
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Cnidarians Have diversified into a wide range of both sessile and floating forms including jellies, corals, and hydras These animals have radial symmetry and diploblastic embryos. The basic body plan of a cnidarian is a sac with a central digestive compartment, the gastrovascular cavity. It has a single opening that functions as both a mouth and anus.
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There are two variations on this body plan: the sessile polyp and the floating medusa . Some cnidarian exist only as polyps. Others exist only as medusas. Still others pass sequentially through both a medusa stage and a polyp stage in their life cycle. Mouth/anus Tentacle Gastrovascular cavity Gastrodermis Mesoglea Epidermis Tentacle Body stalk Mouth/anus Medusa Polyp Figure 33.5 The cylindrical polyps , such as hydras and sea anemones , adhere to the substratum by the aboral end and extend their tentacles, waiting for prey. Medusas (also called jellies ) are flattened, mouth-down versions of polyps that move by drifting passively and by contacting their bell-shaped bodies.
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Cnidarians are carnivores that use tentacles arranged in a ring around the mouth to capture prey and push the food into the gastrovascular chamber for digestion (Figure 33.6). Batteries of cnidocytes on the tentacles defend the animal or capture prey. These cells contain stinging components called nematocysts that can discharge a thread that can inject poison into the prey, or stick to or entangle the target.
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Muscles and nerves exist in their simplest forms in cnidarians. Cells of the epidermis and gastrodermis have bundles of microfilaments arranged into contractile fibers . Movements are controlled by a non-centralized nerve net
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This note was uploaded on 05/04/2011 for the course BIO 119 taught by Professor O'donnellandspear during the Spring '07 term at SUNY Geneseo.

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biol_119__lecture_3__9-4-09 - Lecture 3, September 9, 2009...

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