CHAPTER 38 NERVOUS AND SENSORY SYSTEMS
Scientific Skills Exercise
Teaching objective: In this exercise, students explore how genetic mutants can be used as
experimental animals and how we can learn about physiology through genotype comparisons in
combination with experimental manipulations. Students evaluate experimental design and
suggest additional controls and manipulations.
Teaching tip: A version of this Scientific Skills Exercise can be assigned in MasteringBiology.
Answers:
1. The experimental variable was the genotype of the transplanted tissue. The researchers used
more than one hamster for each procedure to assess whether the differences in cycle period
4. The lack of restoration of rhythmic activity may have been due to individual differences in
circadian response or differences in surgical procedures. For example, the transplanted SCN may
Suggested Answers for End-of-Chapter Essay Questions
See the general information on grading short-answer essays and a suggested rubric at the
beginning of this document.
8. Scientific Inquiry
The injury eliminated motor control of the hands. To distinguish between these hypotheses, you
9. Focus on Evolution
As humans, we define intelligence based on our thought processes, just as we define the visible
10. Focus on Organization
See the general information on grading short-answer essays and the suggested rubric at the
beginning of this document.
Sample key points:
The lens is clear, allowing transmission of light.
Sample top-scoring answer:
The lens of the human eye, a disk formed from protein, exhibits three adaptations that are crucial
11. Synthesize Your Knowledge
Having more olfactory receptor cells is likely to provide an increased sensitivity to odorants. If
there is a greater variety in the cell types as well, there could be an increased ability to