Which of the following chemical groups is not used to construct a DNA molecule?
(a) five-carbon sugar
(b) phosphate
(c) nitrogen-containing base
(d) six-carbon sugar
(d)
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Many substances have been shown to accumulate in ecosystems, including the pesticide dichlorodiphenyltrichloroethane (DDT), which was described in the 1960s bestseller, Silent Spring, by Rachel Carson. DDT was a commonly used pesticide before its dangers became known. In some aquatic ecosystems, organisms from each trophic level consumed many organisms of the lower level, which caused DDT to increase in birds (apex consumers) that ate fish. Thus, the birds accumulated sufficient amounts of DDT to cause fragility in their eggshells. This effect increased egg breakage during nesting and was shown to have adverse effects on these bird populations. The use of DDT was banned in the United States in the 1970s. This is an example of which of the following?
a. biomass b. concentrated bioproductivity c. biomagnification d. bioentropy
Alternation of generations in plants refers to the alternation of:
a. diploid and haploid stages. b. male and female stages. c. meiotic and mitotic stages. d. spore and seed stages. e. thallus and leaf stages.
Which English economist predicted that the rapid growth of human populations would soon exceed Earth's capacity to support it?
A) Hutton B) Wallace C) Lyell D) Mendel E) Malthus
The most common mechanism for sympatric speciation in plants is
A. punctuated equilibrium. B. geographic isolation. C. disruptive selection. D. spontaneous mutation. E. polyploidy.