The hormone ______ produced by the _______ gland promotes sleep and inhibits gonadal activity
a. melatonin; pineal
b. thyroxin; thyroid
c. cortisol; adrenal
d. insulin; islets of Langerhans
e. oxytocin; hypothalamus
A; The pineal gland functions in light sensing and seems to help program the body for its daily rhythms. It releases melatonin in the evening, and melatonin seems to induce sleep if people take a dose of it. Moreover a drop in melatonin levels seems correlated with increased gonadal activity. Thyroxin (choice b) maintains the basal metabolic rate. Cortisol (choice c) is involved in stress responses. Insulin (choice d) is important in removing excess glucose from the blood and getting it into cells. Oxytocin is important in milk let-down and triggering uterine contractions.
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If a mitotic poison is administered to the cells of the apical meristem, this substance would
freeze all the cells at the metaphase portion of mitosis. What would you then expect to happen?
a. Accelerated growth would occur. b. No growth would occur. c. There would be no change in the growth rate. d. The growth rate would depend on environmental conditions
For most species that exhibit sexual dimorphism the
selection of a mate is the responsibility of the a. male. b. parents. c. female. d. larger individual, no matter the species. e. more colorful individual.
________ are small organic molecules that are required in minute amounts for metabolism
Fill in the blank(s) with the appropriate word(s).
If two populations of the same species live in different environments for a long time, what will likely occur?
A. Neither population will be able to adapt to its environment. B. One population will evolve better adaptations than the other. C. Evolution can result in enough differences between the populations that they can't interbreed. D. Different mutations may occur in each population, but natural selection will favor the same adaptations in both. E. Natural selection will preserve the same adaptations in both, preventing random differences from appearing.