Which element is not one of the four most common elements found in organisms?
a. hydrogen
b. oxygen
c. carbon
d. helium
e. nitrogen
ANSWER: d
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Cells in the G2 stage of the cell cycle have ________ as cells of the same species in the G1 stage.
A) twice as many crossovers B) twice as many chromatids C) half as many chromatids D) the same number of chromatids E) half as many chromosomes
Which of the following atmospheric gas is changing the global climate?
A. ozone B. water vapor C. carbon dioxide D. hydrogen E. oxygen
Microevolution, or evolution at its smallest scale, occurs when
A) an individual's traits change in response to environmental factors. B) a community of organisms changes due to the extinction of several dominant species. C) a new species arises from an existing species. D) a population's allele frequencies change over a span of generations.
Why is acetogenesis from H2 and CO2 more favored than methanogenesis in termites?
a. Unlike methanogens, acetogens are able to use other substrates, such as sugars, as electron donors for energy metabolism. b. Unlike acetogens, methanogens are able to use other substrates, such as methyl groups, as electron donors for energy metabolism. c. Termite acetogens can better colonize the H2-rich termite gut center, whereas methanogens are restrictedto the wall. d. both a and c