Which of the following is the major reason why it has been difficult to treat viral infections with chemotherapeutic agents?
A. Viruses use the metabolic machinery of their hosts, which limits many of the potential points of attack.
B. Viruses have no metabolism and therefore offer no selective point of attack.
C. Viral metabolism resembles that of their hosts so there is no selective point of attack.
D. Actually, viruses are not difficult to treat with chemotherapeutic agents.
Answer: A
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The concept that most morphological changes in species occur gradually over long periods of time is known as the
____.
a. phyletic gradualism hypothesis b. principle of convergent evolution c. punctuated equilibrium hypothesis d. unified theory of evolution e. concept of adaptive radiation
When the substrate is bound to the enzyme, the shape of the enzyme may change slightly, leading to
A. an induced fit. B. more possible products of the reaction. C. more permanent binding through intimate total contact. D. a great range of possible catalytic activities. E. a greater supply of activation energy.
Type II survivorship curves ____.
A. are characteristic of humans and elephants B. indicate a fairly constant rate of death at all ages C. indicate a high mortality rate in the very young D. are characteristic of species in which most individuals live a relatively long life and die of old age E. are typical of species with high biotic potentials
Which of the following species of hominin is the most recent to have become extinct?
A) Homo erectus B) Homo neanderthalensis C) Homo ergaster D) Homo habilis