Thinking Scientifically

1. How can the musculoskeletal systems of diverse vertebrate species consist of the same molecules, cells, and tissues, and have similar organization, yet also be adapted to a particular species’ way of life?

2. What role does fluid play in hydroskeletons, cartilage, and synovial joints?

3. The aerobics instructor chants, “Just concentrate, and feel your muscles expand and contract.” Is her statement an accurate description of muscle action? Why or why not?

4. Why are voluntary muscles in invertebrates termed striated, but in vertebrates called skeletal?

5. In some European nations, ratio of fast- to slow-twitch fibers is used as a predictor of athletic success in certain events. Athletes give small sample of muscle tissue to test for twitch fiber proportions. How would the ratio probably differ between a champion sprinter and a long distance runner?

6. A father wants to test his healthy daughter’s muscles to determine the percentage of slow-twitch and fast-twitch muscle fibers to decide if she should try out for soccer or cross-country (long-distance) running. Do you think this is a valid reason to test muscle tissue? Why or why not?

Addional Questions

1. Osteogenesis imperfecta is an inherited disorder that affects the skeleton. Children with the condition lack a form of collagen that is normally part of bone. Their bones break very easily, even when they make normal movements, and may even break before birth. How can the molecular defect causing osteogenesis imperfecta explain the symptoms?

2. Archaeologists have uncovered skeletal remains of our humanlike ancestors in Ethiopia. Examination of some of the bones suggests that the remains represent four types of humans. Microscopic examination shows that the bone masses of some skeletons are about 30% less than those of the other type, and the skeletons with the lower bone mass have broader front pelvic bone than those of the heavier bone mass group. Within the two groups defined by bone mass and pelvic bone shape, smaller skeletons have bones with evidence of epiphyseal plates, but larger bones have only a thin line where the epiphyseal plates should be. Identify the four types of individuals in this find.

3. If a bedridden hospital patient is not moved for a long time, the patient’s cartilage begins to degenerate. What is the molecular basis for this?

4. Spondylitis is a painful condition in which ligaments in the backbone harden. How could this impair the functioning of the backbone? What might the symptoms be?

5. A man exercises intensively, building up his muscles. He believes he will pass this hypertrophy to his future children. Why is he incorrect?