MRSA is the acronym for methicillin-resistant Staphylococcus aureus. Many of the strains of the common bacterium are also resistant to other antibiotics in use today. The resistance is linked to a collection of genes carried on plasmids that are passed from one bacterium to another by conjugation. Suppose a newly discovered, chemically different antibiotic is used in place of methicillin. Which of the following would be the most likely effect on Staphylococcus aureus antibiotic resistance?

Life history traits that are selected for at high population densities are called K-selected traits, or ______ traits. 

On a large volcanic island, researchers are studying a population of annual herbaceous plants. Which of the following observations best supports the prediction that speciation will occur within the existing plant population?

The graph is titled Wolf and Elk Population Sizes in Yellowstone National Park. The horizontal axis is labeled Year, and has values from left to right of 1993 to 2006. Each year is represented with a tick mark, and the years 1995, 2000, and 2006 are labeled appropriately. The left vertical axis is labeled Wolf Population and has values from bottom to top of 0 to 20 in increments of five. The right vertical axis is labeled Elk Population and has values from bottom to top of 0 to 120, in increments of 20. Two separate lines with points are shown on the graph. The first line is dashed and is labeled Elk. The second line is solid and is labeled Wolves. The approximate values of each respective line are as follows. Year, 1993; Elk Population, 90. Year, 1993; Wolf Population, 2. Year, 1994; Elk Population, 95. Year, 1994; Wolf Population, 2. Year, 1995; Elk Population, 80. Year, 1995; Wolf Population, 2. Year, 1996; Elk Population, 75. Year, 1996; Wolf Population, 6. Year, 1997; Elk Population, 60. Year, 1997; Wolf Population, 7. Year, 1998; Elk Population, 55. Year, 1998; Wolf Population, 8. Year, 1999; Elk Population, 57. Year, 1999; Wolf Population, 11. Year, 2000; Elk Population, 70. Year, 2000; Wolf Population, 10. Year, 2001; Elk Population, 60. Year, 2001; Wolf Population, 16. Year, 2002; Elk Population, 55. Year, 2002; Wolf Population, 17. Year, 2003; Elk Population, 40. Year, 2003; Wolf Population, 18. Year, 2004; Elk Population, 38. Year, 2004; Wolf Population, 22. Year, 2005; Elk Population, 44. Year, 2005; Wolf Population, 18. Year, 2006; Elk Population, 28. Year, 2006; Wolf Population, 12. Figure 1. Wolf and Elk Population Sizes in Yellowstone National Park The graph is titled Browsing of Aspen in Yellowstone National Park. The horizontal axis is labeled Year, and has values from left to right of 1993 to 2006. Each year is represented with a tick mark, and the years 1995, 2000, and 2006 are labeled appropriately. The vertical axis is labeled Percent Aspen Browsed and has values from bottom to top of 0 to 100 in increments of twenty. Two separate lines with points are shown on the graph. The first line is dashed and is labeled Riparian. The second line is solid and is labeled Uplands. The approximate values of each respective line are as follows. Year, 1998; Percent Aspen Browsed in Uplands, 98. Year, 1998; Percent Aspen Browsed in Riparian, 98. Year, 1999; Percent Aspen Browsed in Uplands, 98. Year, 1999; Percent Aspen Browsed in Riparian, 96. Year, 2000; Percent Aspen Browsed in Uplands, 96. Year, 2000; Percent Aspen Browsed in Riparian, 93. Year, 2001; Percent Aspen Browsed in Uplands, 95. Year, 2001; Percent Aspen Browsed in Riparian, 85. Year, 2002; Percent Aspen Browsed in Uplands, 93. Year, 2002; Percent Aspen Browsed in Riparian, 83. Year, 2003; Percent Aspen Browsed in Uplands, 91. Year, 2003; Percent Aspen Browsed in Riparian, 81. Year, 2004; Percent Aspen Browsed in Uplands, 87. Year, 2004; Percent Aspen Browsed in Riparian, 48. Year, 2005; Percent Aspen Browsed in Uplands, 73. Year, 2005; Percent Aspen Browsed in Riparian, 25. Year, 2006; Percent Aspen Browsed in Uplands, 65. Year, 2006; Percent Aspen Browsed in Riparian, 16. Figure 2. Browsing of Aspen in Yellowstone National Park The graph is titled Growth of Aspen in Yellowstone National Park. The horizontal axis is labeled Year, and has values from left to right of 1993 to 2006. Each year is represented with a tick mark, and the years 1995, 2000, and 2006 are labeled appropriately. The vertical axis is labeled Aspen Height in centimeters, and has values from bottom to top of 0 to 250 in increments of fifty. Two separate lines with points are shown on the graph. The first line is dashed and is labeled Riparian. The second line is solid and is labeled Uplands. The approximate values of each respective line are as follows. Year, 1998; Aspen Height in Centimeters in Uplands, 35. Year, 1998; Aspen Height in Centimeters in Riparian, 35. Year, 1999; Aspen Height in Centimeters in Uplands, 32. Year, 1999; Aspen Height in Centimeters in Riparian, 38. Year, 2000; Aspen Height in Centimeters in Uplands, 29. Year, 2000; Aspen Height in Centimeters in Riparian, 48. Year, 2001; Aspen Height in Centimeters in Uplands, 35. Year, 2001; Aspen Height in Centimeters in Riparian, 58. Year, 2002; Aspen Height in Centimeters in Uplands, 45. Year, 2002; Aspen Height in Centimeters in Riparian, 75. Year, 2003; Aspen Height in Centimeters in Uplands, 50. Year, 2003; Aspen Height in Centimeters in Riparian, 95. Year,2004; Aspen Height in Centimeters in Uplands, 70. Year, 2004; Aspen Height in Centimeters in Riparian, 135. Year, 2005; Aspen Height in Centimeters in Uplands, 90. Year, 2005; Aspen Height in Centimeters in Riparian, 180. Year, 2006; Aspen Height in Centimeters in Uplands, 120. Year, 2006; Aspen Height in Centimeters in Riparian, 225. Figure 3. Growth of Aspen in Yellowstone National Park Wolves, a top predator, were reintroduced to Yellowstone National Park in 1995 after a 50-year absence. In a multiyear study, the numbers of wolves and elk were monitored. The data are shown in Figure 1. In two different environments scientists monitored the percent of aspen trees browsed by herbivores (Figure 2) as well as the growth of the trees (Figure 3). The upland environments consist mostly of flat forested areas. The riparian environments are areas along streams with steep, wooded banks. Which of the following models best predicts the effect on the ecosystem if a deadly communicable disease is introduced into the wolf population?

Histone methyltransferases are a class of enzymes that methylate certain amino acid sequences in histone proteins. A research team found that transcription of gene R decreases when histone methyltransferase activity is inhibited. Which scientific claim is most consistent with these findings?

A researcher is investigating the relationship between the existing species diversity in a community and the ability of an introduced nonnative species to destabilize the community. Which of the following graphs is most consistent with the claim that communities with high diversity are more resistant to change than are communities with low diversity?

The horizontal axis is labeled “Beak Depth, in millimeters,” and the numbers 6 through 14, which are the 9 categories, are indicated. The vertical axis is labeled “Number,” and the numbers 0 through 300, in increments of 50, are indicated. The data represented by the bars are as follows. Note that all values are approximate. Beak Depth, 6 millimeters: 15. Beak Depth, 7 millimeters: 20. Beak Depth, 8 millimeters: 60. Beak Depth, 9 millimeters: 265. Beak Depth, 10 millimeters: 290. Beak Depth, 11 millimeters: 90. Beak Depth, 12 millimeters: 5. Beak Depth, 13 millimeters: 0. Beak Depth, 14 millimeters: 1. The graph above shows the distribution of beak depth in a finch population that had been living on an island under conditions of normal rainfall. During a subsequent drought, the small seeds normally eaten by the finches were less available. Most of the available seeds were large seeds that could be eaten most easily by finches with deep beaks. Which of the following graphs best predicts the distribution of beak depth in the finch population after several years of drought?

A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 49 percent of the animals display a recessive trait (bb), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants.  What is the frequency of allele b in the gene pool?

Some cells release active signaling proteins when membrane-bound precursor proteins are cleaved by proteolytic enzymes. The signaling proteins can then bind to receptors on the surface of a target cell, thereby activating an intracellular signaling pathway and eliciting a response from the target cell. This mechanism of activating receptor-binding signaling proteins has been observed in a variety of organisms from bacteria to humans. Many of the enzymes responsible for proteolysis of membrane-bound precursor proteins have been isolated and characterized. Which of the following questions would be most appropriate to investigate whether the proteolytic enzymes are evolutionarily conserved among species?

A scientist is using an ampicillin-sensitive strain of bacteria that cannot use lactose because it has a nonfunctional gene in the lac operon. She has two plasmids. One contains a functional copy of the affected gene of the lac operon, and the other contains the gene for ampicillin resistance. Using restrictions enzymes and DNA ligase, she forms a recombinant plasmid containing both genes. She then adds a high concentration of the plasmid to a tube of the bacteria in a medium for bacterial growth that contains glucose as the only energy source. This tube (+) and a control tube (-) with similar bacteria but no plasmid are both incubated under the appropriate conditions for growth and plasmid uptake. The scientist then spreads a sample of each bacterial culture (+ and -) on each of the three types of plates indicated below. The columns show the different media on the plates starting with glucose medium, then glucose medium with ampicillin and then glucose medium with ampicillin and lactose. The rows are bacterial strain with added plasmid, also labeled positive, and bacterial strain with no plasmid, also labeled negative. The plates are labeled number one through number six, with one, two and three with positive bacteria on the media in order, and four, five and six with negative bacteria on the media in order. Plate one is bacteria with plasmid on glucose medium. Plate two is bacteria with plasmid on glucose medium with ampicillin. Plate three is bacteria with plasmid on glucose medium with ampicillin and lactose. Plate four is bacteria without plasmid on glucose medium. Plate five is bacteria without plasmid on glucose medium with ampicillin. Plate six is bacteria without plasmid on glucose medium with ampicillin and lactose The columns are lactose medium and lactose medium with ampicillin. The rows are bacterial strain with added plasmid, also labeled positive, and bacterial strain with no plasmid, also labeled negative. The plates are labeled number seven through number ten. Plate seven is bacteria with plasmid on lactose medium. Plate eight is bacteria with plasmid on lactose medium with ampicillin. Plate nine is bacteria without plasmid on lactose medium. Plate ten is bacteria without plasmid on lactose medium with ampicillin. If the scientist used the cultures to perform another experiment as shown above, using medium that contained lactose as the only energy source, growth would most likely occur on which of the following plates?