Cellular crawling motion is accomplished by:
A. the polymerization of microfilaments along
the leading edge in response to an activated
cell surface receptor.
B. the depolymerization of microfilaments
along the leading edge in response to an
activated cell surface receptor.
C. the contraction of microfilaments along the
leading edge in response to an activated cell
surface receptor.
D. the polymerization of microfilaments along
the trailing edge in response to an activated
cell surface receptor.
E. All of these choices can contribute to rapid
shifting of direction of crawling motion.
A
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Treponema pallidum
A. is the organism that causes syphilis. B. is a spirochete. C. can be more easily viewed with dark-field illumination. D. has become less virulent over time. E. All of the above are correct.
An animal’s fight-or-flight response is controlled by which of the following?
a. sympathetic nervous system b. frontal lobe c. parasympathetic nervous system d. occipital lobe
The Cambrian Explosion provided a wealth of fossil remains for scientists to uncover. Many of the animals from this time period had tough skins or shells. This would
a. protect the animal from osmotic pressure. b. be a disadvantage for these organisms and lead to their death and fossil formation. c. protect the animal from predators. d. make these animals more desirable to predators. e. allow the animals to move into different environments easily.
In a tube-within-a-tube body plan, what forms the outer tube?
a. The body wall b. The wall of the gastrovascular cavity c. The vacuolar membrane d. The intestinal wall e. The gizzard wall