In many animals, changes in melatonin secretion patterns trigger seasonal adjustments in behavior or appearance. Explain how melatonin levels affect singing in male songbirds
What will be an ideal response?
In some male songbirds, long winter nights lead to an increase in melatonin secretion. The rise in melatonin indirectly prevents singing and other courtship behaviors by slowing secretion of the male sex hormone testosterone. As long as the level of testosterone stays low, the bird will not sing. In the spring, there are fewer hours of darkness, so the melatonin level in the bird's blood declines, testosterone rises, and the bird begins to sing.
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The chytrid Batrachochytrium dendrobatidis is responsible for a disease that
a. is sexually transmitted in humans. b. has wiped out many species of frogs. c. infects wheat, rye, and other grain crops. d. is killing trees in temperate forests. e. kills millions of humans each year.
The first complete plant genome to be sequenced was that of
a. Phaseolus vulgaris (kidney bean). b. Arabidopsis thaliana (thale cress). c. Zea mays (corn). d. Capsella burse-pastoris (shepherd's purse). e. Oryza sativa (rice).
Four of the five answers are ways by which animals remove water and/or unwanted solutes. Select the exception
a. excretion in urine b. secretions c. exhalation d. elimination in feces e. bleeding
Which step in the evolution of life is the most
complex and probably occurred last? a. formation of DNA b. formation of protein-RNA systems c. formation of membrane-bound proto-cells d. spontaneous formation of organic compounds under abiotic conditions e. formation of ATP