In a controlled experiment, researchers manipulate one variable at a time.
What was the experimental variable in this study? - ANSWERSthe genotype of the transplanted tissue
Why did the researchers use more than one hamster for each procedure? - ANSWERSto assess whether the differences in cycle...
Bio 111 Exam 3 Questions & Answers
In a controlled experiment, researchers manipulate one variable at a time.
What was the experimental variable in this study? - ANSWERSthe genotype of the
transplanted tissue
Why did the researchers use more than one hamster for each procedure? -
ANSWERSto assess whether the differences in cycle period before and after transplant
were greater than the variation in cycle period from animal to animal
What traits of the individual hamsters would likely have been controlled across the
treatment groups? - ANSWERSage and sex
For the wild-type hamsters that received τ SCN transplants, what would have been an
appropriate control? - ANSWERStransplant the SCN from one wild-type hamster to
another wild-type hamster
What general trends does the graph reveal about the period of the circadian rhythm in
transplant recipients? - ANSWERSIt was similar to that of the donor, whether the
recipient was wild-type or τ mutant.
What can you conclude about the role of the SCN in determining the period of the
circadian rhythm? - ANSWERSThe SCN determines the period of the circadian rhythm.
In 20% of the hamsters, there was no restoration of rhythmic activity following the SCN
transplant.
Can you be confident of your conclusion about the role of the SCN based on data from
80% of the hamsters? Why or why not? - ANSWERSYes. The data from 80% of the
hamsters are very consistent. In the other 20%, the transplanted SCN may not have
established functional connections with the recipient's brain.
Suppose researchers identified a mutation that caused hamsters to have no rhythmic
activity. Also suppose you transplanted the SCN of wild-type hamsters into hamsters
with this mutation.
What result would you expect from this experiment, assuming that the SCN determines
the period of the circadian rhythm? - ANSWERSThe recipients would have rhythmic
activity with a period of about 24 hours.
What result would you expect if you transplanted the SCN of τ hamsters into no-
rhythmic-activity mutants? - ANSWERSThe recipients would have rhythmic activity with
a period of about 20 hours
Carbon dioxide enters the blood at the _____. - ANSWERScapillaries of the head,
forelimbs, abdominal organs, and hind limbs
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