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?

The first graph is titled fur color distribution immediately after release, with y-axis labeled frequency. There are three bars representing gray, brown and black mice. The gray and black mice have very low bars at low frequency, and the brown mice have a tall bar with high frequency. The second graph is titled fur color distribution after twenty years, with y-axis labeled frequency. The gray mice have the highest frequency, the brown mice have a mid-level frequency, and the black mice have very low frequency. A group of mice was released into a large field to which no other mice had access. Immediately after the release, a representative sample of the mice was captured, and the fur color of each individual in the sample was observed and recorded. The mice were then returned to the field. After twenty years, another representative sample of the mice was captured, and the fur color of each individual in the sample was again recorded. Which of the following best explains the change in the frequency distribution of fur color phenotypes in the mouse population, as shown in the figures above?

LAC OPERON STRUCTURE The L A C operon has a region labeled Regulatory Gene that contains loci P subscript 1 and l a c 1. The L A C operon has a 2nd, separate region that contains five loci, in order from left to right on the DNA strand, P subscript l a c, operator, l a c Z, l a c Y, l a c A. The functions of the loci of the lac operon shown in the diagram are described in the table below. Functions of the loci of the lac operon Locus Function PI Attachment site for RNA polymerase lacI Encodes a repressor protein that prevents transcription of the structural genes of the lac operon Plac Attachment site for RNA polymerase Operator Binding site for the repressor protein lacZ Encodes beta-galactosidase, the enzyme that digests lactose to glucose and galactose lacY Encodes lactose permease, the channel through which lactose moves into the cell lacA Encodes galactoside transacetylase The diagram above represents a segment of the E. coli chromosome that contains the lacI gene and part of the lac operon, a coordinately regulated set of genes that are required for the metabolism of lactose. The presence of lactose, which causes the repressor to be released from the operator, results in increased transcription of the lac operon. Bacterial cells that contain green fluorescent protein (GFP) will fluoresce under ultraviolet light. Which of the following is the most likely outcome of replacing the lacZ gene in the E. coli lac operon with the gene encoding GFP?

Phytochromes are molecules that change light stimuli into chemical signals, and they are thought to target light-activated genes in plants. A study was conducted to determine how certain cell proteins were made in a plant cell using a phytochrome. Figures 1 and 2 represent findings from the study. In the first part of the diagram, inactive phytochrome P r in the cytoplasm becomes active phytochrome P f r that enters the nucleus in the presence of red light. The next part of the diagram shows that P f r is bound to P I F 3 that is bound to a G Box Promoter and that P f r is also bound to a Transcriptional Complex that is bound to a T A T A box on DNA. A bent arrow above a shaded rectangle to the right of the T A T A box points to the right and is labeled Transcription. An arrow points from the shaded box to a circle labeled M Y B. In the last part of the diagram, the M Y B labeled circle is bound to another Promoter and also contacts a Transcriptional Complex that is bound to a T A T A box on DNA. A bent arrow above a shaded rectangle to the right of the T A T A box points to the right and is labeled Transcription. An arrow points from the shaded box to the label Cell Proteins. Figure 1. Phytochrome response to exposure to red light In the first part of the diagram, active P f r in the cytoplasm becomes inactive P r in the presence of far red light. The next part of the diagram shows an arrow labeled Far Red Light pointing to free P r in the nucleus and away from both P I F 3 bound to a G Box Promoter and a Transcriptional Complex bound to a T A T A box on DNA. A label above a shaded rectangle to the right of the T A T A box reads No Transcription. A second label below the shaded box reads M Y B Type Transcription Factor. The last part of the diagram shows another Promoter and a T A T A box on DNA. Nothing is bound to the promoter, and a Transcriptional Complex is bound to the T A T A box. A label above a shaded rectangle to the right of the T A T A box reads No Transcription. A label below the shaded rectangle reads Other Genes. Figure 2. Phytochrome response to exposure to far‑red light Use the response models shown in Figures 1 and 2 to justify the claim that phytochromes regulate the transcription of genes leading to the production of certain cellular proteins.