Bacterial conjugation involves
A. a bacteriophage carrying donor DNA to the recipient cell.
B. new progeny cells with genes from two parent bacterial cells.
C. a donor cell with a plasmid that synthesizes a pilus.
D. naked DNA fragments from a lysed donor cell taken up by a recipient cell.
Answer: C
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Which of the following best reflects what we know about how the flu virus moves between species?
A) The flu virus in a pig is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected. B) A flu virus from a human epidemic or pandemic infects birds; the birds replicate the virus differently and then pass it back to humans. C) An influenza virus gains new sequences of DNA from another virus, such as a herpesvirus; this enables it to be transmitted to a human host. D) An animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates, the virus is passed to a new species such as a bird, and the virus mutates again and can now be transmitted to humans.
What observation does the Red Queen Hypothesis seek to provide an explanation for?
A. Rate of extinction of taxa is fairly constant over time. B. Rates of extinction vary substantially between different groups of organisms. C. Lineages become more resistant to extinction the longer they have been present. D. Rates of extinction vary substantially between different groups of organisms, and lineages become more resistant to extinction the longer they have been present. E. Immediately after speciation, risk of extinction is very high, but it eventually levels out.
Why is the left side of the heart stronger than the right side of the heart?
A) The left side pumps blood to the right side of the body, which has more muscle mass. B) The right side pumps only to the lungs, and the left side pumps blood around the whole body. C) The right side pumps blood only to the brain, and the left side pumps blood around the whole body. D) The left side receives more oxygen from the lungs.
The tension-length curve for a muscle fiber is the same as that for a muscle
a. true b. false