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ap bio quiz 3

Figure 1. Effect of light intensity (μmol·m-2·s-1) on the pH of a solution containing algae

Students investigated the effect of light intensity on the rates of photosynthesis and cellular respiration in algae. They placed equal numbers of algal cells into test tubes containing a solution at pH7.40. The test tubes were divided into four treatment groups, and each treatment group was exposed to a different light intensity. The pH in the tubes was measured every 10 minutes and used as an indicator of CO2 concentration because CO2 produces an acidic solution when dissolved in water (Figure 1).

Algae that are exposed to 100 μmol  of light have a greater rate of photosynthesis than of cellular respiration over time.

The deep ocean floor communities contain very little life. In constant darkness, the water at these depths hovers around . Sparsely distributed in this environment are hydrothermal vent ecosystems. Superheated water streams out of the vents at temperatures approaching . These waters are rich in inorganic materials, including carbon dioxide and hydrogen sulfide. Hydrothermal vent zones have a density of organisms 10,000 to 100,000 times greater than found on the surrounding seafloor.

Scientists have studied these vents to determine the energy source for these communities and the identity of the primary producers in the perpetual darkness of the ocean floor. As expected, they found a total absence of photosynthetic organisms at all vents, identifying mats of bacteria as the producers of the carbon compounds that are used by the rest of the community for growth, repair, and as an energy source.

Which of the following describes how the vent bacteria harvest energy to produce organic compounds for use by the vent community?

The bacteria function as chemoautotrophs, extracting energy from hydrogen-rich inorganic molecules.

A scientist is attempting to provide support for the hypothesis that was the first genetic material. Which of the following would be a workable alternate hypothesis?

RNa can be observed to self-replicate without the assistance of proteins, while DNAA researcher claims that increased atmospheric carbon dioxide levels cause increased growth rates in plants.

A researcher claims that increased atmospheric carbon dioxide levels cause increased growth rates in plants.

Which of the following statements best supports the researcher’s claim?

Atmospheric carbon dioxide is the raw material for photosynthesis, which plants rely on for producing sugars and other organic compounds.

Assume there are 50,000 joules (J) of energy available in trophic level II in the figure. According to the conventional model of energy flow in ecosystems, which of the following statements correctly describes the flow of energy in the system?

Trophic level IV has approximately 500 J of available energy.

Dr. 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?

The temperatures and pressures found in hydrothermal vents resemble conditions described in currently accepted origins of life hypotheses.

Figure 1 represents the feeding relationships between selected organisms in the Chesapeake Bay. Decades of overharvesting have reduced the populations of both blue crabs and rockfish. However, recent efforts have increased the number of rockfish in the bay. Based on Figure 1, what is the most likely result of the increase in rockfish?

The population of blue crabs will decrease because predation by rockfish will increase.

Many scientists claim that the synthesis of the first organic molecules from inorganic precursors was possible because of the highly reducing atmosphere found on primitive Earth.

Which of the following is an appropriate null hypothesis that could be used when investigating the claim?

The synthesis of organic molecules from inorganic molecules is possible under current atmospheric oxygen levels as well as those found on primitive Earth.

Which of the following best explains why there are seldom more than five trophic levels in a food chain.

Energy is lost from each trophic level.