The masseter muscles originate on your cheekbones and insert into the posterior corners of the mandible (the lower jaw bone) underneath your ears. Will contraction of the masseter muscles open or close your jaw?
A. Close
B. Open
Answer: A
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Which is true of aminoglycosides?
A. They are bacteriostatic. B. They irreversibly bind to the 30S ribosomal subunit. C. They block peptidoglycan synthesis. D. They are bactericidal. E. They irreversibly bind to the 30S ribosomal subunit AND they are bactericidal.
When pollen from one species lands on the stigma of a flower from another species, the pollen tube typically ____
a. does not develop b. forms, but the sperm cannot penetrate the egg c. forms and grows to the ovary, but then stops d. forms, but the sperm are killed e. forms and the egg is usually fertilized, but the embryo rarely grows
Usually the female is more discriminating than the male when it comes to mating. However, in bush crickets, the opposite is the case. Why is this?
a. Male bush crickets are prettier than female bush crickets. b. A male bush cricket must bring the female a large offering of food in order for the female to accept him as a mate. c. The male contributes a massive amount of energy to the female during mating—his ejaculate makes up about one-fourth of his body weight. d. Male bush crickets have tremendous variation in the desirability of their territories. e. Male bush crickets accept the newly fertilized zygotes from the female and incubate them.
An accidental spill of a pesticide locally wiped out the most abundant species of butterfly in coastal California. Most of the bird species in the area had fed on this butterfly, but they switched prey to moths, and thus the birds showed only a small
decrease in population size. The butterflies were a/an: A) keystone species, and thus they were driven to extinction very easily. B) endangered species. C) pioneer species. D) ecological dominant, but they were not a keystone species.