Lab 5 - Crayfish Anatomy

Lab 5 - Crayfish Anatomy - Anil Kanungo BIO 206L Thursday...

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5/8/2009 Anil Kanungo BIO 206L Thursday 6-10pm Lab #5: Crayfish Anatomy Lab Study Questions: Crayfish: 1.) Describe the functions of the external structures of the crayfish that you identified in this exercise and discuss how they are involved in feeding (including obtaining food) and avoiding predators One of the most distinguishable external structure on the crayfish are the chelipeds. They are large pincers used for grasping/tearing food and also for defense. The crayfish also has antenna sensory structures that assist in locating food. The walking legs and uropod/telson section may assist in mobility to help the crayfish escape predators 2.) Trace the pathway of a crayfish’s meal and its digested nutrients from the mouth to the abdominal flexor muscle. What molecule must be picked up along this pathway in order for the muscle cell to obtain energy from the food particles and where is the molecule absorbed into the blood? Food first enters through the mouth where it then progresses through the esophagus to the stomach and is absorbed using enzymes from the digestive gland. Glucose must be picked up to obtain energy. It must be filtered through the pyloric stomach and digested prior to being absorbed into the blood. 3.) Consider a crayfish that has a potential meal move into its field of vision. Trace the pathway of the nerve impulse that is generated by this sensory stimulus until it affects muscle responses. Which body parts and appendages would likely be stimulated to respond? A nerve impulse would be sent from the antennae and/or compound eye through the cerebral ganglion to the ventral nerve cord. There the impulse would be sent to the appropriate muscles to generate a response. The impulse would most likely stimulate muscles associated with mobility (walking legs, abdominal flexor,etc) and muscles associated with preying (chelipeds, mandibular muscle, etc). 4.) Vertebrates, with their closed circulatory systems, typically have a blood volume that is 5-10% of the total body volume. Would you expect the percentage that blood volume constitutes of total body volume to be lower or higher in an animal such as the crayfish, that has an open circulator system? Explain your answer. I would expect the blood volume of an animal such as a crayfish to be higher than that of a vertebrate. Since crayfish have open circulatory system, the blood is more spread out and it takes more blood to reach all of the necessary tissues and organs. It would be harder for the blood to reach its destination so it would take more of it to do so.
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