NPB 128 Final Study Questions Set III

NPB 128 Final Study Questions Set III - NPB 128 Final Study...

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NPB 128 Final Study Questions Set III 1. Sex steroids induce sexual dimorphism in different ways in different species: provide an example of estrogen suppressing a male trait, estrogen inducing a female trait, and androgen inducing a male trait. a. Estrogen decreses SF1 and Sox9 in female turtles. Estrogen and DDT feminized alligators. Estrogen and aromatase suppressed maleness even at male temperatures for reptiles. Estrogen suppresses elaborate plumage in the common pheasant. b. Estrogen induces ova production. Estrogen induces coloration in reed frog females. Female secondary characteristics (breast). c. Androgens (11KT) induce male salmon size, color, and jaw morphology. Androgens induce antler growth. Testosterone causes the wolfian duct to stay intact and form the epididymis, vas deferens, and seminal vesicles. DHT causes the formation of the penis and prostate. 2. Why are many vertebrate species subject to seasonal control of reproduction? a. For many animals, it is optimal for the offspring to be born during the spring when food is abundant, and the temperature is favorable. Therefore, depending on the animal’s gestation period, they should mate at a specific time to anticipate the offspring being born during the spring. b. Humans evolved equatorially, when the seasons don’t differ that much from each other, so we can mate at any time of the year. Food source and stress determines our ability to mate and reproduce. 3. Describe the evidence for the importance of the pineal gland and melatonin in controlling the seasonality of testicular size and function in the golden hamster. In your opinion, does this evidence support physiological role for the pineal in this process? a. Light inhibits the production of melatonin. So melatonin levels are high during periods of low daylight. b. In the naturally occurring seasonal breeding cycle of the golden hamster, melatonin levels are highest during the winter months. This is due to the short day length. Also during this time, testicular size/weight as well as reproductive capacity is the lowest. c. If melatonin were removed from the hamster’s body, then testis and reproductive capacity would remain high regardless of the daylength. d.
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NPB 128 Final Study Questions Set III - NPB 128 Final Study...

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