Speciation occurs ____.
A. after populations become reproductively isolated
B. when mutations generate observable differences
C. when transitional forms develop between different populations
D. when natural selection pressures reach their maximum
E. randomly as mutations build up in a population
Answer: A
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Functionally speaking, a nerve impulse is
a. a flow of electrons along the outside of the plasma membrane of a neuron. b. the movement of cytoplasmic elements through the core of the neuron. c. a series of changes in membrane potential. d. a lengthening and shortening of the membrane extensions of a neuron. e. a turning on and off of the sodium-potassium pumps of a neuron.
Refer to the accompanying figure. What is the structure at point 6 in this life cycle?
a. zygote b. gamete c. zoospore d. endospore e. pseudopod
Which of the following human cells may host HIV?
Which of these carries the most energy?
a. ADP b. ATP c. NADH d. NAD+