Asdfg Essay

849 WordsJan 4, 20134 Pages
LABORATORY EXERCISE #8 HOW ARE THE STRUCTURES OF THE EARTHWORM ADAPTED TO THEIR FUNCTIONS? INTRODUCTION The earthworm is a member of the Phylum Annelida, a group of animals with many repeating body parts called segments. The earthworm is a nocturnal animal which prefers rich, moist soil. By ingesting and digesting dead organic matter in the soil, and by aerating the soil it burrows, the earthworm plays an important part in improving the fertility of your garden or the farmer’s field. As you dissect the earthworm today, you will see a hollow body cavity and many well-developed organ systems. As animals in the different Phyla have gotten larger, we see the development of increasingly complex organ systems to help maintain homeostasis and to communicate with all parts of the body. STUDENT OBJECTIVES 1. Observe the external and internal structures of the earthworm. 2. Relate the earthworm structures to their function. 3. Become familiar with terms relating to body orientation. PRE-LAB QUESTIONS 1. Why do we say earthworms have a “tube within a tube” structure? 2. Describe ingestion, digestion, and egestion in earthworms. 3. Earthworms are hermaphroditic. Explain. 4. Briefly describe the the following locations on the earthworm: dorsal, ventral, lateral, medial, anterior, posterior MATERIALS Dissection kit, dissecting pan, pins, hand lens, preserved worm, dissection manual, charts of earthworm structure, live earthworm if available for observations. PROCEDURE Work in pairs. Use the dissection manual for additional information and diagrams. I. External Observation 1. Pick up the earthworm. Observe the color and the segments along the whole length of the body. There is a smooth band which almost encircles the worm. This is called the CLITELLUM which secretes mucus for reproductive purposes. The clitellum is always

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