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Name: _______________________________________ EARTHWORM DISSECTION Prelab Before beginning this lab, please go to: http://mhhe.com/biosci/genbio/virtual_labs/BL_14/BL_14.html . Read the introduction and then click on the lab manual and read it. What are the characteristics of members of the phylum Annelida (page 755 in textbook)? What does the name Annelida mean? Looking at figure 27-10 on page 792, explain what is meant by a closed circulatory system and identify the structures (organs) of this system. Earthworms are hermaphrodites. What does this mean? External Anatomy http://mhhe.com/biosci/genbio/virtual_labs/BL_14/BL_14.html Label the following external structures of the earthworm in the diagram below: mouth, clitellum, setae, anus, and opening of the sperm ducts Front side of EW Observartions 1. Feel the side and bottom of the earthworm. These nubby structures are called setae. What is their function? 2. Observe the color of the dorsal surface and the ventral surface. What observation can you make and how does this help the earthworm survive in its environment? Internal anatomy Label the following structures of each system of the earthworm’s internal anatomy a. Digestive System- mouth, pharynx, crop, gizzard, and intestines b. Circulatory System- aortic arches (hearts), dorsal blood vessel, and ventral blood vessel c. Nervous System- brain and ganglia of ventral nerve cord d. Excretory System- nephridia Dorsal side Observartions 3. How does the wall of the crop compare to the wall of the gizzard? Analysis and Conclusions 1. Explain how an earthworm demonstrates cephalization (look up the term) 2. How does the clitellum aid in earthworm reproduction? (Think about its structure and what it does.) 3. Give two different ways that earthworms are adapted for their life in the soil. a. b. 4. When dissecting the earthworm, why did we use an upward pointed scissor and not a razor blade? 5. Describe how an earthworm is poorly adapted to life in the soil. 6. Why are earthworms found on pavement during and after a heavy rain? Think about what happens to soil in the rain.
