Low pH is an important deterrent to pathogens in the:
a. stomach only
b. mouth only
c. vagina only
d. stomach and mouth
e. stomach and vagina
e
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You want to know whether cookies made with unbleached flour taste better than cookies made with bleached flour; which of the following has the strongest experimental design to test this question?
A. Make two batches of cookies, one with bleached flour and one with unbleached flour; one taster tries both types and ranks which type they like best. B. Make two batches of cookies, one with bleached flour and one with unbleached flour; twenty tasters try both types and rank which type they like best. C. Make two batches of cookies, one with bleached flour and one with unbleached flour; twenty tasters try both types without knowing which ones they are eating and rank which type they like best. D. Make two batches of cookies, both with bleached flour; one taster tries both types and ranks which type they like best.
Horses and donkeys can interbreed, but their offspring (mules) are infertile. This is an example of what kind of reproductive isolating mechanism?
A. pre-zygotic, behavioral isolation B. pre-zygotic, temporal separation C. pre-zygotic, ecological separation D. post-zygotic E. post-zygotic, ecological separation
In __________, one of the sperm cells in the pollen
tube fertilizes the egg, forming a zygote; the other fuses with the endosperm mother cell and gives rise to __________. Fill in the blank(s) with the appropriate word(s).
The site where RNA polymerase attaches to the DNA molecule to start the formation of mRNA is called a(n)
A. exon. B. operator. C. promoter. D. operon.