Rr. Robert Hazen has worked to develop a hypothesis that explains the origin of life on Earth. His work has focused on hydrothermal vents, which are cracks in the ocean floor. Water heated by molten rock beneath the crust escapes from these vents at very high temperatures, producing hot, high‑pressure environments at the vents on the ocean floor. In order to provide evidence that these vents may be areas where life originated, which of the following states a null hypothesis Hazen might have used to begin his research?

Figure 1 represents part of a process essential to gene expression. The two strands of the helix are paired at each end but are separated in the central portion. Bases of the nucleotides are indicated for the entire length of each strand. The left end of the upper strand is labeled 5 prime, and the right end is labeled 3 prime. The left end of the lower strand is labeled 3 prime, and the right end is labeled 5 prime. The lower strand is also labeled Strand X. An additional single strand of nucleotides that is complementary to the lower DNA strand is also present on the left and central portions of the figure. The sequence of the strand, from the left 5 prime end to the right 3 prime end, is as follows: A U G C C G C A A U C U G U U C A C G C A C U C A U G U G. Above the strand an arrow labeled Direction of Synthesis points along the strand from left to right. Figure 1. Model of process involved in gene expression. Which of the following best explains what strand X represents?

In an experiment on the effects of deforestation of a portion of a northern temperate deciduous forest, all the trees were removed from a small mountainside watershed area and herbicides were applied for three years to prevent regrowth. Measurements of the concentration of calcium (an important nutrient) in runoff water were taken both before and after the deforestation. Monthly measurements also were made in a similar watershed in another part of the same forest that had been left undisturbed. The findings are displayed in the graph below. The figure shows a graph in quadrant one titled Monthly Measurements Of Calcium Concentration In Runoff Water. The horizontal axis has every month from June, 1965 to May, 1968, with a tick mark at each month. The vertical axis is labeled calcium ion concentration in runoff water in milligrams per liter, from zero to eleven in increments of one. The time of deforestation is marked at December 1965. There is a dashed line labeled losses from undisturbed watershed that remains at one milligram per liter with only slight fluctuations from June 1965 until the end of the graph in May 1968. There is a solid line labeled losses from disturbed watershed. The calcium ion concentration in runoff water for losses from disturbed watershed is approximately one milligram per liter from June 1965 until May 1966. There is a sharp increase from May to July where the ion concentration reaches seven milligrams per liter, then drops to five in August, and continues rising with fluctuations until October 1966 when it reaches a concentration of nine milligrams per liter. There is a decrease over time, with fluctuations, to six milligrams per liter by May 1967, when the concentration increases rapidly to above eleven, peaking in September 1967, then decreasing steadily with small fluctuations to approximately four milligrams per liter in May 1968. Which of the following is best supported by the data?

Erwin Chargaff investigated the nucleotide composition of DNA. He analyzed DNA from various organisms and measured the relative amounts of adenine (A), guanine (G), cytosine (C), and thymine (T) present in the DNA of each organism. Table 1 contains a selected data set of his results. Table 1. Nucleotide composition of selected organismsample DNA from Organism %A %G %C %T %(G+C) %(A+T) Octopus 33.2 17.6 17.6 31.6 35.2 64.8 Chicken 28.0 22.0 21.6 28.4 43.7 56.4 Rat 28.6 21.4 20.5 28.4 42.9 56.0 Grasshopper 29.3 20.5 20.7 29.3 41.2 58.6 Wheat 27.3 22.7 22.8 27.1 45.5 54.4 Which of the following statements best explains the data set?

Phytoplankton (black line) are important because they occupy the bottom of the food web absorbing CO2, functioning as a carbon sink. A scientist suggests that an El Niño event in early 1998 caused a significant decrease in the abundance of phytoplankton that year in the equatorial Pacific Ocean. The horizontal axis is labeled Year, and the years 1990 through 2000, in increments of 2, are indicated. The vertical axis is labeled, Relative Plankton Density. A key indicates that one line represents zooplankton and the other line represents phytoplankton. The data represented in the graph are as follows. Note, all data are approximate. Data for zooplankton. The line begins approximately one third of the way up the vertical axis above the origin and trends slightly upwards and to the right, fluctuating up and down across the length of the horizontal axis with upward spikes approximately every two years, and a significant downward spike at the year 1998 that falls to just above the horizontal axis. Data for phytoplankton. The line begins just below the midpoint on the vertical axis, above the origin, and trends slightly upwards and to the right, fluctuating up and down across the length of the horizontal axis, staying above the line for zooplankton and with a significant downward spike at the year 1998 that falls one third of the way up the vertical axis, comes back up by 1999, and remains fairly constant after that. Figure 1. Relative abundance of plankton over time in the eastern equatorial Pacific Ocean Which of the following observations would best support this alternative hypothesis?

There is a horizontal rectangle that is labeled D N A. The rectangle is divided into 9 boxes. From left to right, the first box is labeled P sub r, the second box is labeled trp R, the third box is labeled promoter, the fourth box is labeled Operator, the fifth box is labeled trp E, the sixth box is labeled trp D, the seventh box is labeled trp C, the eighth box is labeled trp B, and the ninth box is labeled trp A. Above the rectangle on the left is a large oval shape labeled R N A Polymerase. An arrow extends from the oval shape to the right and points to an X that is positioned above the boxes labeled Promoter and Operator. An irregular shape that looks like half of a circle and which is labeled R is positioned on top of the boxes labeled Promoter and Operator. A smaller oval shape labeled T is positioned partly on top of the shape labeled R. Underneath the rectangle, an arrow points downward from the box labeled trp R to a small, horizontal rectangle labeled trp R m R N A. On the left side of the rectangle is a 5 prime and a dash. On the right side of the rectangle is a dash and a 3 prime. An arrow points from the rectangle to a large oval shape labeled R. The large oval shape has a smaller oval shape cut out of it. To the left of the large oval shape are the words Inactive Repressor. A horizontal arrow points from the large oval shape to an irregular shape that looks like half of a circle and which is labeled R. A smaller oval shape labeled T is positioned partly on top of the shape labeled R. To the left of the irregular shape are the words Active Repressor. Above and to the left of the irregular shape is a small oval shape labeled T. A curved arrow extends from the shape labeled T down and to the right, eventually merging with the horizontal arrow that extends from the large oval shape on the left to the irregular shape on the right. A curved arrow extends from the irregular shape up and counterclockwise to point to the same shape that is positioned on top of the boxes labeled Promoter and Operator. There is a key below the figure that reads R equals Repressor molecule, T equals Tryptophan molecule, P sub R equals Promoter for the trp R gene, trp R equals Repressor gene, and Operator equals Binding site for repressor molecule. The Trp operon is a coordinately regulated group of genes (trpA–trpE) that are required for tryptophan biosynthesis in E. coli. Based on the figure above, which of the following correctly describes the regulation of the Trp operon?

There are two small black, shaded circles on the plate. The one on the left is labeled A and is surrounded by an unshaded circle on the agar. There is also another small black dot next to the circle. The other circle is labeled P and has no other visible change on the agar. A sterile agar plate, I, is streaked with a pure culture of bacteria by means of aseptic techniques. Paper discs treated with the antibiotics Aureomycin (A) and penicillin (P) are placed at opposite sides of the plate, as shown in the diagram above. The plate is examined after a 24-hour incubation period, and a clear ring is discovered around disc A, but not around disc P. Within the clear ring around disc A, a single bacterial colony with physical characteristics like those of the pure culture is observed. A second sterile agar plate, II, is then streaked with this single colony and also incubated with antibiotics. Which of the following would most likely be observed in plate II after 24 hours?

All of the following were likely present on the primitive Earth during the evolution of self-replicating molecules EXCEPT

In plants, members of the euphorbia family and the cactus family have separate origins, with the euphorbia evolving in the desert regions of Asia and Africa and the cacti in the desert regions of the Americas. Both have fleshy stems adapted for water storage, protective spines, and leaves that are greatly reduced or absent. The similarities between these two families of plants represent an example of

The food web consists of the following 9 organisms or groups of organisms, from bottom to top and left to right: Plants, Squirrels, Mice, Insects, Spiders , Insectivorous Birds, Foxes, and Hawks and Owls, Snakes. From bottom to top, the food web is organized as follows. From Plants, arrows extend to Squirrels, Mice, and Insects. From Squirrels, arrows extend to Foxes, and Hawks and Owls. From Mice, arrows extend to Hawks and Owls, and Snakes. From Insects, arrows extend to Spiders, and Insectivorous Birds. From Spiders, an arrow extends to Insectivorous Birds. From Insectivorous Birds, arrows extend to Hawks and Owls, and Snakes. Which of the following changes to the environment will most likely lead to more energy entering the meadow community represented above?