Jaws evolved during the Silurian period by modification of _____ in a jawless ancestor
1.the cartilaginous skeleton
2.the second pair of gill arches
3.gill slit support structures
4.the spiracle
3
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Meselson and Stahl's experiment followed
A) the distribution of different-weighted DNA over multiple generations of bacteria. B) the ability of a protease or nuclease to stop the transmission of DNA over generations. C) viruses injecting their DNA into bacteria. D) DNA sequences in people who are politically liberal compared to those who are sometimes politically conservative.
Nitrogen-fixing bacteria convert N2 into
A. nitrates. B. ammonium ions. C. nitrites. D. carbon dioxide. E. methane.
From an evolutionary perspective, why is sexual reproduction advantageous over asexual reproduction?
A) Sexual reproduction produces less genetic diversity than asexual reproduction. B) Asexual reproduction minimizes differences, so natural selection can act more easily. C) Sexual reproduction is faster and easier than asexual reproduction. D) Sexual reproduction produces greater genetic diversity than asexual reproduction.
Since the Pleistocene ice age, deserts have been gradually forming in the southwestern United States. As the original lakes and rivers of this area shrank into isolated streams and springs, the fishes living in them developed a strong potential for:
A) hybrid inviability. B) temporal isolation. C) hybrid sterility. D) speciation.