Infection occurs when
A. a person swallows microbes in/on food.
B. pathogens enter and multiply in body tissues.
C. a person inhales microbes in the air.
D. contaminants are present on the skin.
E. All of these choices are correct.
Answer: B
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Compared to the air above a nearby land mass, how would the air above a large body of water be?
A) cooler in winter B) warmer in summer C) cooler in summer D) the same, unless wind is blowing
The chromosome of a bacterial cell possesses the following genotype with regard to the lac operon: I?O+Z+Y?A?. This bacterial cell would
A) make ?-galactosidase in the presence of lactose. B) make ?-galactosidase independently of lactose. C) make ?-galactosidase and galactoside permease in the presence of lactose. D) make transacetylase in the presence of lactose. E) make no lac gene products.
Which postulate of natural selection is deliberately enforced by dog breeders using artificial selection?
a. Individuals in a population vary. b. Survival and reproduction are not determined by chance. c. Traits are passed from parent to offspring. d. Some individuals fail to survive and reproduce.
When a New England farm is abandoned, its formerly plowed fields first become weedy meadows, then shrubby areas, and finally forest. This sequence of plant communities is an example of
A) evolution. B) a food chain. C) secondary succession. D) primary succession.