1. The lionfish is a venomous fish found primarily in the Red Sea and the Indian Ocean. In the 1990s,lionfish were accidentally released into the Atlantic Ocean, where they found abundant resources and favorable environmental conditions.Which of the following scenarios is most likely to result in the lionfish having a major impact on the communities into which they were introduced?
(A) With no natural predators, the lionfish population will become very large.
(B) Some native species of invertebrates will develop a resistance to lionfish venom.
(C) Random mating will allow the lionfish population to reach Hardy-Weinberg equilibrium.
(D) A virus that specifically infects lionfish will become more prevalent.
2. Cell communication is critical for the function of both unicellular and multicellular eukaryotes.Which of the following is likely true of cell signaling?
(A) Cell signaling uses the highest molecular weight molecules found in living cells.
(B) Cell signaling has largely been replaced by other cell functions in higher mammals.
(C) Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes.
(D) Cell signaling functions mainly during early developmental stages.
3. A colony of termites was exposed to an atmosphere of 100 percent oxygen for three days. The insects were not immediately harmed by the treatment, but the protozoa that lived in the termites’ guts were eliminated. The treated termites continued to behave normally and to eat wood, but they began to starve after a short time. When the treated termites were instead fed wood contaminated with the feces of untreated termites, the treated termites regained the ability to digest wood and no longer starved. The best analysis of the results of the experiment is that
(A) infection with protozoa causes the termites to switch to fermentation
(B) cooperative interactions between the termites and the protozoa allow termites to extract energy from wood to survive
(C) the termite immune system eliminates protozoa from the gut
(D) termites digest protozoa as their main source of energy
4. Ethylene is an organic compound produced by ripening fruits. In a controlled experiment, researchers found that ethylene gas stimulated the ripening process in newly harvested fruits. Which of the following describes the most likely connection between natural ethylene production and fruit ripening?
(A) As a result of metabolic inactivity, newly harvested fruits are unable to absorb ethylene gas from the atmosphere.
(B) Ethylene gas is a chemical signal through which ripening fruits trigger the ripening process in other fruits.
(C) Because of normal phenotypic variation, only some of the fruits in a given generation are expected to produce ethylene gas.
(D) The rate of ethylene gas production by ripening fruits is an indicator of the relative age of an ecosystem.
5. Water in a pond contaminated with the weed killer atrazine is suspected of inhibiting metamorphosis in northern leopard frogs. A team of scientists collected fertilized northern leopard frog eggs from a different pond that is not contaminated. Which of the following is the best experimental design to determine whether atrazine is responsible for inhibiting metamorphosis in northern leopard frogs?
(A) Place half of the fertilized eggs in a pool of water with the same concentration of atrazine as the contaminated pond and place the other half of the fertilized eggs in a pool of water that has no atrazine. Monitor the development of the embryos through metamorphosis into adulthood.
(B) Place all of the fertilized eggs in a pool of pond water with the same concentration of atrazine as the contaminated pond and compare the number of frogs that reach metamorphosis to those that reach adulthood in the contaminated pond.
(C) Allow all fertilized eggs to develop into adults. Expose one-third of the frogs to one-half of the concentration of atrazine in the contaminated pond and expose another one-third of the frogs to the same concentration of atrazine as the contaminated pond. Leave the last one-third of the frogs in water with no atrazine and note any adverse changes in the physical condition of the atrazine-treated frogs in three months.
(D) Divide the fertilized eggs into three groups and expose each group to a different concentration of atrazine. Release the eggs back into the contaminated pond and check for metamorphosis after three months.
1. Catechol, a natural substance found in plants, reacts with oxygen to produce benzoquinone and water, as represented by the chemical equation above. The reaction is catalyzed in plants by the enzyme polyphenol oxidase. Accumulation of benzoquinone in plant tissue results in the gradual appearance of a brown color. A student observes that lemon juice (pH 2) slows the browning of apple slices. The student claims that lemon juice slows the browning process by altering the activity of polyphenol oxidase. To test the claim, the student distributes equal amounts of a dilute catechol solution to 6 identical test tubes. The pH of each solution was adjusted as shown in the table, and the initial absorbance was recorded. Equal amounts of polyphenol oxidase were added to each reaction tube. After 10 minutes at room temperature the absorbance of 389 nm light (A389) was measured for each sample. Solutions containing greater concentrations of benzoquinone absorb more light. The changes in A389 are shown in the table below.
(a) On the axes provided, construct an appropriately labeled bar graph to analyze the effect of pH on polyphenol oxidase activity.
(b) Based on the experimental results, estimate the optimal pH of the enzyme. Explain your estimate by connecting the experimental results to the structure and function of proteins.
(c) Propose an appropriate control treatment for the experiment, and describe how the control treatment would increase the validity of the results.
(d) Genetic engineering can be used to disrupt specific genes in the genome of an organism. Predict how the browning of apple slices would be affected in a strain of apples that was genetically engineered to lack functional copies of the gene encoding polyphenol oxidase. Justify your response.