Question from campbell biology chapter 23:
72) swine are vulnerable to infection by bird flu virus and human flu virus, which can both be present in an individual pig at the same time. when this occurs, it is possible for genes from bird flu virus and human flu virus to be combined. if the human flu virus contributes a gene for tamiflu resistance (tamiflu is an antiviral drug) to the new virus, and if the new virus is introduced to an environment lacking tamiflu, then what is most likely to occur?
a) the new virus will maintain its tamiflu-resistance gene, just in case of future exposure to tamiflu.
b) the tamiflu-resistance gene will undergo mutations that convert it into a gene that has a useful function in this environment.
c) if the tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency.
d) if the tamiflu-resistance gene confers no benefit in the current environment, and has no cost, the virus will become dormant until tamiflu is present.

2. if scientists identify an animal with bilateral symmetry and no segmentation, which phylum can it definitely not belong to? a. roundworms b. annelids c. mollusks d. flatworms

What causes temperature extremes in the desert

In 1959, doctors began using the powerful antibiotic methicillin to treat infections of staphylococcus aureus, but within two years, methicillin-resistant strains of s. aureus (mrsa) appeared. how did the resistant strains of s. aureus emerge? in 1959, doctors began using the powerful antibiotic methicillin to treat infections of staphylococcus aureus, but within two years, methicillin-resistant strains of s. aureus (mrsa) appeared. how did the resistant strains of s. aureus emerge? staphylococcus aureus bacteria that were able to synthesize cell walls using a protein that was not affected by methicillin survived the methicillin treatments and reproduced at higher rates than did other individuals. over time, these resistant individuals became increasingly common. in response to treatment of staphylococcus aureus infections with methicillin, some bacteria began to synthesize cell walls using a protein that was not affected by methicillin. these bacteria survived the methicillin treatments and reproduced at higher rates than did other individuals. over time, these resistant individuals became increasingly common. in response to treatment of staphylococcus aureus infections with methicillin, bacterial populations gradually began to synthesize cell walls using a protein that was not affected by methicillin.