Thinking Scientifically

1. In an episode of the television series, Star Trek, three members of the crew of the starship USS Enterprise meet an enemy who dehydrates each one into a small box. He then rearranges the boxes and crushes one of them. He later attempts to restore the people to life but only two of them reappear. What biological principle does this action illustrate?

2. For the following real-life examples, state whether or not the scientific method was followed. If it was not, indicate which of the following specific faults occurred:

     a. Experimental evidence does not support conclusions

     b. Inadequate controls

     c. Biased sampling

     d. Inappropriate extrapolation from the experimental group to the general population

     e. Sample size too small

(1) “I ran 4 miles every morning when I was pregnant with my first child,” the woman told her physician, “and Jamie weighed only 3 pounds at birth. This time, I didn’t exercise at all, and Jamie’s sister weighed 8 pounds. Therefore, running during pregnancy must cause low birth weight.”

(2) Eating food high in cholesterol was found to be dangerous for a large sample of individuals with hypercholesterolemia, a disorder of the heart and blood vessels. It was concluded from this study that all persons should limit dietary cholesterol intake.

(3) Osteogenesis imperfecta (oi) is an inherited condition that causes easily fractured bones. In a clinical study, 30 children with oi were given a new drug for 3 years. The children all showed increased (improved) bone density, lowered incidence of fractures compared to before treatment began, and less fatigue. The conclusion: The drug is effective in treating oi.

(4) Researchers studied HIV in blood and semen from 11 HIV-infected men. In 8, the virus was resistant to several medications, and in 2 of these men, virus from the blood was resistant to the class of drugs called protease inhibitors, but virus from semen was not resistant. The researchers concluded that protease inhibitors do not reach the male reproductive organs.

Additional Questions and Terms

1. What general principle discussed in the chapter does the function of aggregated endothelium illustrate in keeping dangerous substances out of the brain?

2. An android is a being that inhabits many science fiction stories. It is engineered from hardware and operates on software with neural networks that impressively mimic the human nervous system, giving the android intelligence, expanded memory, and self-awareness. Is an android a person or a nonliving device? Which characteristics of life does it have? Which does it lack?

3. A chemical manufacturing plant closes because of a leak of a toxic substance. To examine the possible health effects of the contamination, researchers ask workers and residents to fill out surveys and list their health problems and record the extent of their exposure to the toxins. What can be learned from this type of study? What are its limitations?