biol_119__lecture_2__9-2-09

biol_119__lecture_2__9-2-09 - Finishing up Chapter 32...

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Finishing up Chapter 32 before moving on to Chapter 33
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A. radial symmetry B. a right and a left side C. a head region D. a dorsal and a ventral surface E. ectoderm Your review question Cephalization" refers to having _____.
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Which of the following has been proposed to account for the Cambrian explosion (independent reading)? A. Predator/prey relationships B. Increase in atmospheric oxygen C. Evolution of the Hox gene complex A. All of the above
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C. Body Cavities In triploblastic animals a body cavity may be present or absent
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What are the benefits of having a body cavity, what roles does it play? 1. Its fluid cushions the internal organs, helping to prevent internal injury . 2. The non-compressible fluid of the body cavity can function as a hydrostatic skeleton against which muscles can work. 3. The presence of the cavity enables the internal organs to grow and move independently of the outer body wall. 4. Creates an enclosed space for the circulation of oxygen and nutrients
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1. Coelomates: A true body cavity is called a coelom and is derived from mesoderm and is surrounded by mesoderm on both sides . Coelomates such as earthworms have a true coelom.
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2. Pseudocoelomates: A pseudocoelom is a body cavity derived from the blastocoel , rather than from mesoderm. Pseudocoelomates such as nematodes have a body cavity only partially lined by tissue derived from mesoderm, but also by tissue derived from endoderm.
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3. Acoelmates: Organisms without body cavities are considered acoelomates. Acoelomates such as flatworms lack a body cavity between the digestive tract and outer body wall.
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True or False: A true coelom is surrounded by mesoderm on both sides.
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D. Protostome and Deuterostome Development Based on certain features seen in early development animals can be categorized as having one of two developmental modes: protostome development or deuterostome development
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D. Protostome and Deuterostome Development Early development of bilateral animals can be categorized as having one of two developmental modes: protostome development deuterostome development
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Many protostomes undergo spiral cleavage , in which planes of cell division are diagonal to the vertical axis of the embryo. Some protostomes also show determinate cleavage where the fate of each embryonic cell is determined early in development. The zygotes of many deuterostomes undergo radial cleavage in which the cleavage planes are parallel or perpendicular to the vertical egg axis. Most deuterostomes show
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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_2__9-2-09 - Finishing up Chapter 32...

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