In 1980, only 1 to 5% of all Staphylococcus aureus isolates were MRSA strains. Now 60 to 70% of S. aureus isolates are MRSA strains. What process is the cause of this situation?

A) stabilizing selection of humans
B) directional selection of humans
C) directional selection of bacteria
D) diversifying selection of bacteria


C

Biology & Microbiology

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You have discovered a previously unidentified plant, and you cultivate it in your lab

You notice that its flowers close when people are talking, yet are open when the lab is relatively quiet. You suspect that this plant may have the ability to hear! Which of the following hypotheses is (are) the most reasonable to explain this phenomenon? I) There is a cell-surface protein on the epidermal cells that becomes phosphorylated in response to vibration by sound waves. II) There are tiny hairs on epidermal cells that bend in response to the vibration of sound waves, triggering an action potential in epidermal cells. III) There is a cell-surface receptor on root cells that becomes phosphorylated when the soil vibrates in response to sound waves. A) only I B) only II C) only III D) only II and III E) I, II, and III

Biology & Microbiology

When David Baltimore’s lab tried to determine how an RNA tumor virus replicates its genome, they

discovered that

a. these viruses can make DNA without an RNA template b. these viruses can make DNA after being treated with RNase c. these viruses can make more RNA genomes from their RNA genome d. an enzyme (reverse transcriptase) makes DNA from RNA e. an enzyme (reverse transcriptase) makes RNA from DNA

Biology & Microbiology

Notochords are found in

a. adult hemichordates (acorn worms). b. adult urochordates (tunicates). c. adult cephalochordates (lancelets). d. a and b only. e. b and c only.

Biology & Microbiology

Which structure, A, B, C, or D, stores and releases calcium?

1.A 2.B 3.C 4.D

Biology & Microbiology