Question
A researcher claims that genetic variation provides organisms with the ability to survive and reproduce in different environments. To support the claim, the researcher makes the following observation: bacteria that contain plasmids (small DNA
molecules) are resistant to a wider range of antibiotics than are bacteria that contain no plasmids.
Which of the following statements best establishes a connection between the observation and the researcher’s claim?
A. Some antibiotics inhibit the synthesis of bacterial cell walls.
B. Some antibiotics inhibit protein synthesis in bacteria cells.
C. Some plasmids cannot exist in a bacterial cell with certain other plasmids.
D. Some plasmids contain antibiotic resistance genes.
▶️Answer/Explanation
Ans: D
Because some plasmids contain antibiotic resistance genes, bacteria that contain plasmids are more likely to be resistant to antibiotics than are bacteria that do not contain plasmids. The observation is evidence that genetic variation in the form of plasmids provides bacteria with the ability to survive and reproduce in different environments.
Question
Phycobiliproteins are a complex of accessory pigments and proteins found in cyanobacteria but not in green algae. A researcher claims that the phycobiliprotein pigments in cyanobacteria allow the cyanobacteria to survive in certain aquatic niches better than green algae can.
Which of the following statements best justifies the researcher’s claim?
A. The additional pigments allow the cyanobacteria to store light energy so that it can be used at night to continue photosynthesis.
B. The additional pigments block light and prevent it from reaching photosynthetic organisms at greater depths, so no photosynthetic organisms can live below the surface waters containing cyanobacteria.
C. The additional pigments require energy and cellular resources to produce, so they can be used as an energy source during times of insufficient light.
D. The additional pigments absorb light at wavelengths that green algae cannot absorb; this may allow cyanobacteria to capture more light energy for photosynthesis than green algae can in certain areas.
▶️Answer/Explanation
Ans: D
Since the phycobiliprotein pigments absorb light wavelengths not absorbed by green algae, cyanobacteria are able to better perform photosynthesis and survive in areas where there is insufficient light at the needed frequencies for green algae to survive
Question
A researcher claims that budding yeast are able to survive in different environments because they produce enzymes that allow them to use different molecules as sources of matter and energy.
Which of the following statements best helps justify the researcher’s claim by providing a relevant example?
A. Yeast cells produce protein kinases, which are enzymes that catalyze the transfer of phosphate groups from ATP to protein substrates.
B. Yeast cells produce DNA polymerases, which are enzymes that catalyze the conversion of free nucleotides into strands of DNA.
C. Yeast cells produce invertase, which is an enzyme that catalyzes the conversion of the disaccharide sucrose into glucose and fructose.
D. Yeast cells produce catalase, which is an enzyme that catalyzes the conversion of hydrogen peroxide into water and oxygen gas.
▶️Answer/Explanation
Ans: C
The disaccharide sucrose is not transported efficiently into yeast cells. By producing the enzyme invertase, budding yeast can use the sucrose, glucose, and fructose in the surrounding environment as sources of matter and energy. As such, the production of invertase by budding yeast is a relevant example that will help justify the researcher’s claim.
Question
A researcher claims that different metabolic pathways allow bacteria to use different molecules as sources of matter and energy.
Which of the following statements best helps justify the researcher’s claim by providing a relevant example?
A. Rhizobia bacteria form close associations with the roots of bean plants.
B. E. coli bacteria reproduce in liquid media containing either glucose or galactose.
C. The antibiotic rifampicin inhibits the growth of some bacterial strains but not of others.
D. Some viruses that infect bacteria reproduce by either the lysogenic cycle or the lytic cycle.
▶️Answer/Explanation
Ans: B
Glucose and galactose are two different monosaccharides that can be used by organisms as sources of matter and energy. The ability of E. coli bacteria to reproduce in liquid media containing either glucose or galactose provides a relevant example that will help justify the researcher’s claim.
Question
Cyanobacteria contain a variety of pigment molecules, as shown in Table 1. As a result, the color of cyanobacteria cultures can vary significantly based on the relative amount of each pigment produced.
A researcher placed a culture of cyanobacteria under green lights. Within a few weeks, the appearance of the cyanobacteria changed from green to red. The researcher claimed the color change in the culture was the result of an adaptation allowing greater photosynthesis.
Which of the following provides the best reasoning to justify the researcher’s claim?
A. In green light, more chlorophyll a molecules are produced, reflecting more light to other cyanobacteria to be used for photosynthesis.
B. In green light, more phycoerythrin molecules are produced, allowing more green light to be absorbed, thus increasing photosynthesis.
C. In green light, cyanobacteria that have more phycocyanin molecules are less likely to survive and reproduce.
D. In green light, cyanobacteria that have more allophycocyanin molecules are more likely to survive and reproduce.
▶️Answer/Explanation
Ans: B
Cyanobacteria exposed to green light would increase production of pigment molecules that can absorb green light and reflect red light, such as phycoerythrin. As a result, the color of the culture would change from green to red. In this way, the organisms are better able to survive under different conditions.