In the 1940’s, Avery MacCleod, and McCarty transformed nonencapsulated bacteria into encapsulated forms by growing the nonencapsulated cells in a culture containing an extract made from dead encapsulated cells. The transformed cells produced colonies of encapsulated bacteria. Three different procedures and their results are outlined below. Procedure I: Extract made from dead encapsulated cells added to culture medium.Nonencapsulated bacteria added to culture medium. Results: Both nonencapsulated and encapsulated bacteria grow. Procedure II: Extract made from dead encapsulated cells treated with protein-degrading enzymes before adding extract to culture medium.Nonencapsulated bacteria added to culture medium. Results: Both nonencapsulated and encapsulated bacteria grow. Procedure III: Extract made from dead encapsulated cells treated with DNAse (an enzyme that selectively destroys DNA) before adding extract to culture medium.Nonencapsulated bacteria added to culture medium. Results: Only nonencapsulated bacteria grow. What was the purpose of treating the extract with protein-degrading enzymes in Procedure II?

Antibiotics can be used to kill the specific pathogenic bacterium, Mycobacterium tuberculosis, that causes tuberculosis. The appearance of antibiotic-resistant strains has made it more difficult to cure M. tuberculosis infections. These antibiotic-resistant bacteria survive and pass on the genes to their offspring, making the resistant phenotype more common in the population. DNA analysis indicates that the genes for antibiotic resistance are not normally present in bacterial chromosomal DNA. Which of the following statements best explains how the genes for antibiotic resistance can be transmitted between bacteria without the exchange of bacterial chromosomal DNA?

The Stanley Miller apparatus demonstrated that organic molecules could assemble spontaneously in an environment lacking free oxygen and containing water, methane, and ammonia in the presence of an abundant energy source, such as an electric discharge. The research was considered supportive of the organic soup hypothesis, which states that the primitive atmosphere provided inorganic precursors from which organic molecules could have been synthesized in the presence of an energy source. Based on subsequent research, the primordial atmosphere was determined to contain less methane and more carbon dioxide. The new data about the composition of the early atmosphere had which of the following effects on origin-of-life hypotheses?

Finch beak depth was measured before and after a severe drought in 1977. The averaged results are shown in Figure 1. After the drought, there were fewer seeds available for the finches to eat and the seeds that did remain were larger and harder to crack open. Researchers claim that when large, hard seeds are the predominate food source, the average beak depth of these finches tends to increase in subsequent generations. The horizontal axis is labeled Beak Depth, in millimeters, and the numbers 7.3 through 11.3, in increments of 0.5, are indicated. The vertical axis is labeled Number of Birds, and the numbers 0 through 50, in increments of 10, are indicated. For most values indicated along the horizontal axis there are two bars. A key indicates that one bar represents values Before the 1977 drought and one represents values After the 1977 drought. The data represented by the histogram are as follows. Note that all values are approximate. Beak Depth, 7.3 millimeters. Before the 1977 drought, 1 bird. After the 1977 drought, 0 birds. Beak Depth, 7.8 millimeters. Before the 1977 drought, 13 birds. After the 1977 drought, 1 bird. Beak Depth, 8.3 millimeters. Before the 1977 drought, 30 birds. After the 1977 drought, 3 birds. Beak Depth, 8.8 millimeters. Before the 1977 drought, 47 birds. After the 1977 drought, 3 birds. Beak Depth, 9.3 millimeters. Before the 1977 drought, 45 birds. After the 1977 drought, 7 birds. Beak Depth, 9.8 millimeters. Before the 1977 drought, 40 birds. After the 1977 drought, 9 birds. Beak Depth, 10.3 millimeters. Before the 1977 drought, 27 birds. After the 1977 drought, 10 birds. Beak Depth, 10.8 millimeters. Before the 1977 drought, 3 birds. After the 1977 drought, 1 bird. Beak Depth, 11.3 millimeters. Before the 1977 drought, 0 birds. After the 1977 drought, 0 birds. Figure 1. Finch beak depth before and after the 1977 drought. Using the evidence provided, which of the following best justifies the researchers’ claim?

_______ is the process in which a protein is assembled at a ribosome.

The amino acid sequence of cytochrome c is exactly the same in humans and chimpanzees. There is a difference of 13 amino acids between the cytochrome c of humans and dogs, and a difference of 20 amino acids between the cytochrome c of humans and rattlesnakes. Which of the following statements is best supported by these data?

Which of the following correctly compares the two processes shown above? The first process is fertilization. A sperm fusing with an egg is shown. The second process is transduction. A five step process is shown. Step 1. Virus attaches to cell surface and inserts viral DNA into cell. Step 2. The cell’s circular DNA is broken into many pieces. Step 3. new viral particles are formed in the cell that include DNA from the host cell. Step 4. One of the new viral particles infects another cell. Step 5. The DNA from the virus is inserted into the circular chromosome of the shot cell.

Which of the following is NOT one of the ways an individual organism can respond to external environmental changes?

Which of the following observations best supports the hypothesis that a large object collided with Earth in a period of time associated with a mass extinction?

A current challenge for doctors involves the bacterial strain Clostridioides difficile, which no longer responds to traditional antibiotic treatments. Which of the following best explains why this particular strain of bacteria is resistant to antibiotic treatment?