At 4:00 p.m. a closed flask of sterile broth is inoculated with 10,000 cells. The lag phase lasts 1 hour. At 9:00 p.m. the culture enters stationary phase with a population of 65 million cells. At what time is the population half maximal?
A. 8:40 p.m.
B. 7:20 p.m.
C. 8:20 p.m.
D. 6:30 p.m.
Answer: A
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Predict how Pasteur's conclusions on spontaneous generation with swan flasks would have changed if he worked with and maintained the flasks in a sterile laminar flow hood
A) Sterilization of the swan flask solutions would not have been necessary to reject spontaneous generation. If he did sterilize the flasks, the spontaneous generation hypothesis would have been supported. B) His incubation times would not have been sufficient to refute spontaneous generation. C) Pasteur's flasks never would have putrefied, and the experiment would not have refuted spontaneous generation. D) Viruses would have still been present, and his conclusion would have been unchanged.
Pathogenicity islands are
A. enzymes like proteases and hemolysins that promote pathogenesis. B. gene clusters that confer the ability to become pathogenic. C. a lymphoid tissue present in the small intestine. D. closely related groups of pathogenic enteric organisms.
The graph in the accompanying figure represents the:a
electromagnetic spectrum b. action spectrum of photosynthesis c. process of cyclic electron transport d. process of noncyclic electron transport e. absorption spectra for chlorophylls a and b
Any blastomere removed from an eight-cell mammalian embryo can develop into a normal late-stage embryo. This finding supports the idea that
A) only the zygote is totipotent. B) the progressive restriction of potency hypothesis applies. C) the first cleavage event must be transverse to the animal-vegetal axis of the zygote. D) cell divisions producing the earliest blastomeres do not result in an asymmetrical distribution of cytoplasmic determinants. E) there is no organizer in mammals.