Of the four chambers of the human heart, which has the thickest walls, and why?
What will be an ideal response?
Left ventricle. The walls are made of muscle, and the left ventricle has to pump the blood to the entire body, which is farther than all the chambers must pump.
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Cephalization is
A. embryonic development of the head in advance of the rest of the body. B. concentration of the sensory organs on the posterior end of the body. C. concentration of the sensory organs on the anterior end of the body. D. an evolutionary degeneration of the head as seen in some parasites. E. a malformation of the head.
Experiments have shown that sap transport peaks ____
a. in the early morning b. by mid-morning c. at midday d. in the evening e. overnight
How does the hypothalamus of the sexually mature human male regulate reproductive hormone levels?
a. The hypothalamus continuously secretes large amounts of GnRH. b. The hypothalamus responds to low levels of testosterone by synthesizing and releasing testosterone. c. The hypothalamus secretes GnRH in brief pulses every two to three hours. d. The hypothalamus secretes LH in response to high levels of testosterone. e. The hypothalamus responds to low levels of GnRH by synthesizing and releasing testosterone.
All of these are known to cause cancer EXCEPT ________
A) some viruses B) DNA repair C) chronic infections D) radiation