Scientists set out to test the hypothesis that the herbicide atrazine is an endocrine disruptor that feminizes male amphibians. They treated male amphibians with atrazine and then compared their circulating testosterone concentration with those of males and females that were not treated with atrazine (controls). The results are shown here (* signifies P<0.05). Was the hypothesis supported? Why or why not?

Design a study to test the hypothesis that the symptoms of jet lag are caused by disruption of normal daily cortisol rhythms.

A strain of mice remains healthy as long as they are fed regularly. After they eat, their blood glucose level rises slightly and then declines to a homeostatic level. However, when these mice fast or exercise, their blood glucose drops dangerously. Which hypothesis best explains their problem? (Explain your choice.)

a. The mice have insulin-dependent diabetes.

b. The mice lack insulin receptors on their cells.

c. The mice lack glucagon receptors on their cells.

d. The mice cannot synthesize glycogen from glucose.

Suppose that during a detailed anatomical study of a marine invertebrate, you found a small, previously undescribed structure. How would you test the hypothesis that the structure is a gland that releases one or more hormones?

The results of Tyrone Hayes's experiments (Module 26.3) were published in a top peer-reviewed journal, yet the validity of his experiments has since been challenged. Using external sources, find out who has challenged the results.

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Ecotourism helps conserve wildlife by increasing the value of wildlife conservation for local people. In Argentina, the world’s largest breeding colony of Magellanic penguins is visited by thousands of tourists every year, causing the penguins to become habituated to the presence of people. Has ecotourism affected the penguins’ ability to respond to stressors? Has it affected the penguins’ secretion of corticosterone?

Corticosterone is a(n):

a. Neurohormone

b. Steroid hormone

c. Amino-acid-derived hormone

d. Polypeptide hormone

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Ecotourism helps conserve wildlife by increasing the value of wildlife conservation for local people. In Argentina, the world’s largest breeding colony of Magellanic penguins is visited by thousands of tourists every year, causing the penguins to become habituated to the presence of people. Has ecotourism affected the penguins’ ability to respond to stressors? Has it affected the penguins’ secretion of corticosterone?

In what part(s) of a target cell would you expect to find corticosterone receptors?

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Ecotourism helps conserve wildlife by increasing the value of wildlife conservation for local people. In Argentina, the world’s largest breeding colony of Magellanic penguins is visited by thousands of tourists every year, causing the penguins to become habituated to the presence of people. Has ecotourism affected the penguins’ ability to respond to stressors? Has it affected the penguins’ secretion of corticosterone?

If penguins in a colony are habituated to the presence of tourists, how would their corticosterone response to being visited by tourists compare to that of penguins in a colony not previously exposed to tourists?

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Ecotourism helps conserve wildlife by increasing the value of wildlife conservation for local people. In Argentina, the world’s largest breeding colony of Magellanic penguins is visited by thousands of tourists every year, causing the penguins to become habituated to the presence of people. Has ecotourism affected the penguins’ ability to respond to stressors? Has it affected the penguins’ secretion of corticosterone?

Scientists tested the hypothesis that penguins habituated to tourists have a blunted stress response overall. They examined the corticosterone response of habituated and non-habituated penguins to another stressor—that of being captured and restrained for 30 minutes. They found that both habituated and non-habituated penguins secreted corticosterone in response to being captured and restrained, but that the level of corticosterone after 30 minutes differed between the groups. The results are shown here (* means P<0.05). Was the hypothesis supported? Explain.