1. People can inherit an inability to smell certain substances, such as freesia flowers, jasmine, skunk scent, and hydrogen cyanide. How could the hypothesis that odors are encoded in combinations of stimulated receptors explain these conditions?

2. Cite two examples of how people who lack one sense can compensate by relying more heavily on another.

3. People who are hearing impaired due to cochlea damage do not suffer from motion sickness. Why not?

4. We have relatively few sensory systems. How, then, do we experience such a diversity of sensory perceptions?

5. Humans love sucrose (table sugar), but armadillos, hedgehogs, lions, and seagulls do not respond to it. Opossums love lactose (milk sugar) but rats avoid it, and chickens hate the sugar xylose, while cattle love it. In what way might these diverse tastes in the animal kingdom be adaptive?

Additional Questions and Terms

1. Loss of the sense of smell is an early symptom of Parkinson disease and Alzheimer disease. How might this information be used to manage these conditions? What additional information is necessary to make medical use of this association?

2. Why is dietary vitamin A good for eyesight?

3. Genetic researchers discovered odorant receptor proteins by searching for proteins in nasal epithelium that resemble rhodopsin. What does the similarity of odorant receptor proteins to the visual molecule rhodopsin suggest about the origin of senses?

4. Why may irritation of the stomach be felt as pain in the upper chest?