lab6_worms_2007

lab6_worms_2007 - Laboratory 6 Annelida and Platyhelminthes...

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Annelida and Platyhelminthes Laboratory 6
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96 Laboratory 6: Annelida OBJECTIVES After completing this lab you will be able to: 1. Explain how earthworms: move support themselves •r e s p i r e obtain and digest food reproduce 2. successfully occupy their ecological niche 3. Explain the earthworm circulatory system LAB PREPARATION In preparation for this laboratory you should do the following: 1. Read and study this laboratory. 2. Read Chapter 32, Chapter 33, and the invertebrate sections of Chapters 40, 41, 42, and 44 in Campbell (7 th Edition). 3. Bring your dissection instruments to lab. 4. Bring your personal protective gear (lab coat, goggles, gloves) to lab. INTRODUCTION This portion of the Biology 172 lab provides an introduction to the structural and functional aspects of animal body plans and the basic themes or strategies employed within each. All animals must accomplish certain basic tasks to survive and reproduce successfully. They must acquire, digest, and metabolize food and distribute its usable products throughout their bodies. They must obtain oxygen, while at the same time ridding themselves of metabolic wastes and undigested materials. The strategies employed by animals to maintain life are very diverse, but they rest upon a few basic principles. Within the constraints imposed by a particular body plan, groups of animals have limited options available to accomplish life’s tasks. For this reason, a few recurring fundamental themes become apparent. In the next series of labs, you will look at representatives of six animal phyla and ask four questions of each. How does it support itself and move? How does it get the oxygen necessary for respiration? How does it get and digest its food? What is its general reproductive strategy? Further, you will look at one or two additional features that are particularly important or apparent in that animal, e.g., circulation in earthworms.
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Laboratory 6: Platyhelminthes 97 As you proceed through each laboratory, remember to continually ask yourself, Why does this animal do the exact same thing, e.g., move, breathe, reproduce, etc., in such a different way from the animal last week? Only by trying to answer this question can you begin to appreciate the complexity of evolution and the subsequent diversity that has arisen. A. Metazoan Phylogeny The metazoa, or multicellular animals, most likely evolved from a common single-celled eukaryotic organism that lived about 700 million years ago. Since then, the metazoa have undergone periods of mind boggling diversification. Some paleontologists estimate that more than 100 different phyla of animals have existed at one point or another; fewer than half of those survive today. If you accept the theory that all animals have a common ancestor, then it seems logical that all animals should have some traits or characters in common with one another. As you look at the diversity of life that surrounds us, it is obvious that all organisms are not alike, but some are more alike than others. Organisms that share common traits appear to be more similar. If two types of organisms share a
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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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lab6_worms_2007 - Laboratory 6 Annelida and Platyhelminthes...

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