CHAPTER 34 CIRCULATION AND GAS EXCHANGE
Scientific Skills Exercise
Teaching objective: Students practice reading and interpreting a histogram showing data from a
study on genetic factors affecting susceptibility to cardiovascular disease.
Teaching tips: A version of this Scientific Skills Exercise can be assigned in MasteringBiology.
plasma LDL levels. Discuss whether it would be possible to design an experiment that would
control for any of these factors.
Answers:
3. You would predict that carriers have a reduced risk for cardiovascular disease because a much
Suggested Answers for End-of-Chapter Essay Questions
See the general information on grading short-answer essays and the suggested rubric at the
beginning of this document.
9. Scientific Inquiry/Interpret the Data
The oxygen dissociation curves indicate that fetal hemoglobin has a higher affinity for oxygen
10. Focus on Evolution
One reason gas exchange would be a challenge for giant insects is the absence of an efficient
system for ventilation. As an insect body increases in size, the tracheae have to become
11. Focus on Interactions
See the general information on grading short-answer essays and the suggested rubric at the
beginning of this document.
Sample key points:
PO2 decreases with increasing altitude.
Obtaining adequate O2 under conditions of low PO2 is difficult.
Sample top-scoring answer:
Because adequate distribution of O2 throughout the body is essential for survival, physiological
control systems have evolved that maintain a close match between the O2 carrying capacity of
12. Synthesize Your Knowledge
Air has a higher O2 content than water and is less dense and less viscous. As a result, being able
to use an air supply underwater is advantageous for the spider. As the spider depletes O2 from the