Purine bases, such as adenine and guanine, have ________ joined ring(s) for their structure, compared to pyrimidine bases, such as cytosine and thymine, that have ________ ring(s) in their structure.
A. one; two
B. two; three
C. two; one
D. three; one
Answer: C
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Stem cells produce successive generations of stem cells through the process of:
a. mitosis b. meiosis c. differentiation d. fertilization e. maturation
Years before Schwann’s pronouncement that a cell
has a life of its own even as a component of a multicellular organism, the cell nucleus had been discovered by a. Robert Hooke. b. Robert Brown. c. Theodor Schwann. d. Rudolf Virchow. e. Anton van Leeuwenhoek.
Anaerobic bacteria often play important roles in bioremediation. Which of the following is NOT an electron acceptor used by anaerobes during biodegradation reactions?
A) H2O B) CO2 C) SO4-2 D) NO3- E) Fe(III)
In a certain ecosystem, rattlesnakes are predators of prairie dogs. An unusually wet spring increases the population of grasses and other plants that prairie dogs eat. The prairie dog population increases. How is the ecosystem most likely to regain stability?
a) the rattlesnake population will start to increase b) the prairie dog population will decrease rapidly c) the prairie dog population will begin to prey on the rattlesnakes d) the rattlesnake population will start to decrease