Question 1: a) What features of Dugesia distinguish its head from its tail? b) What is the difference between the eyes of most animals you are familiar with and the eyespots of Dugesia? c) How does the head of Dugesia move differently from the tail? d) Does Dugesia move randomly or in an apparent direction? e) How is Dugesia adapted for directional movement? f) How does a flatworm respond when touched with a probe? g) Do the planaria move toward or away from light? h) Where is the feeding tube located? Why is this unusual for bilaterally symmetrical organisms? i) Is this gastrovascular cavity of Dugesia a simple sac? How is it divided and what advantage do these divisions offer? j) Consider objective 1 listed at the beginning of this exercise. How could being monoecious contribute to evolutionary success of flatworms in their environment? k) Planarians have a head. In biological terms, what constitutes a �head�? How does it relate to objectives 1, 4, and 7? l) Planaria lack specialized gas-exchange organs. How do you think planaria accomplish this task? Question 2: a) How does the shape of the digestive sac of Opisthrochis compare with that of Dugesia? b) How does the position of the mouth of Dugesia and flukes compare? Question 3: a) Consider objective 1 listed at the beginning of this exercise. How could the production of large numbers of eggs contribute to the evolutionary success of flatworms in their environment? Question 4: a) How does the shape of Schistosoma differ from that of other flukes you have studied? Question 5: a) How does a scolex compare in size to a proglottid near the scolex? Near the posterior end? b) Tapeworms have no digestive system or mouth. How, then, do they obtain food? c) Examine figure 37.8 and its caption carefully. Which proglottids, mature or gravid, occur closest to the scolex? d) What is the difference between a mature and gravid proglottid? e) Consider objective 1 listed at the beginning of this exercise. Is having a scolex significant to a fundamental process for tapeworms? For which process, and how is it significant? f) Tapeworms are specialized. Would you expect specialists to have a unique morphology? Why? Question 6: a) How does the number of body cavities of nematodes compare with that of flatworms? b) What are the advantages of a digestive tract having a separate entrance and exit? c) Female Ascaris are more numerous than males. Why might this be adaptive? Question 8: a) The cuticle of Ascaris is flaky and tough. Consider objective 1 listed at the beginning of this exercise. What might be an adaptive advantage of a thick and tough cuticle? b) Where do the internal organs of Ascaris attach to the body wall? c) How does the diameter of the female reproductive tract change? d) Are any sensory organs evident in Ascaris? Why would this be adaptive?