Unit 0

Some scientists claim that amphibians are currently experiencing a period of mass extinction. Which of the following should be included in an alternative hypothesis that would best support this claim?

• The current extinction rate of amphibians compared with the background rate of extinction as determined by the fossil record

• The extinction rate of amphibians in the century compared with the extinction rate of amphibians during the century

• The number of species of amphibians currently alive compared with the number of amphibian species known to be extinct

• The number of new amphibian species being discovered per year compared with the number of amphibian species becoming extinct during the same time period

Students investigated the effect of light on the carbon cycle in aquatic ecosystems by performing the controlled experiment summarized below. The students placed equal amounts of water (pH 7.0) from a large aquarium in glass beakers. The students transferred aquatic plants from the aquarium to several of the beakers, and then they placed equal numbers of the beakers in the light or the dark (Figure 1: groups I and II). Similarly, the students transferred goldfish from the same aquarium to other beakers, and then they placed equal numbers of those beakers in the light or dark (Figure 1: groups III and IV). Finally, the students placed an equal number of beakers containing water only in the light or dark (Figure 1: groups V and VI).

 

After exposing the samples to light or dark for one hour, the students recorded the pH of the water in each beaker. Carbon dioxide dissolved in water will lower the pH of an aqueous solution. In the experiment, the students used changes in pH to monitor changes in the amount of carbon dioxide in the water. For each treatment group, the students calculated the mean pH and standard error, as documented in the table below.

To investigate whether an organism in the study is capable of both photosynthesis and respiration, a comparison of which treatment groups is most appropriate?

• I and II

• II and IV

• III and V

• IV and VI

Students investigated the effect of light on the carbon cycle in aquatic ecosystems by performing the controlled experiment summarized below. The students placed equal amounts of water (pH 7.0) from a large aquarium in glass beakers. The students transferred aquatic plants from the aquarium to several of the beakers, and then they placed equal numbers of the beakers in the light or the dark (Figure 1: groups I and II). Similarly, the students transferred goldfish from the same aquarium to other beakers, and then they placed equal numbers of those beakers in the light or dark (Figure 1: groups III and IV). Finally, the students placed an equal number of beakers containing water only in the light or dark (Figure 1: groups V and VI).

 

After exposing the samples to light or dark for one hour, the students recorded the pH of the water in each beaker. Carbon dioxide dissolved in water will lower the pH of an aqueous solution. In the experiment, the students used changes in pH to monitor changes in the amount of carbon dioxide in the water. For each treatment group, the students calculated the mean pH and standard error, as documented in the table below.

The results for treatment groups V and VI could suggest which of the following questions about the design of the experiment?

• • Do the glass beakers prevent light from reaching the test samples?

• • Is the method used for measuring pH harmful to aquatic organisms?

• • Is the availability of carbon dioxide a limiting factor in aquatic ecosystems?

• • Does the aquarium water contain living microorganisms?

A massive increase in the growth of a specific species of algae resulted in record-breaking levels of a potentially dangerous toxin being released into the water. A researcher hypothesizes that the unusual growth of this algal species was caused by an increase in water temperature. The researcher designs an experiment to test the hypothesis. Which of the following is the dependent variable in the researcher’s experiment?

• The growth of the algae

• The temperature of the water

• The concentration of toxin in the water

• The different species of algae growing in the water

Thrips are insects that feed on rose pollen. Scientists noted that the thrips population increased in the spring and decreased dramatically during the summer. The researchers hypothesized that food abundance was the limiting factor for the population. Which of the following types of data would be most useful for the scientists to collect at regular intervals on a designated test plot of rose plants?

• Amount of sunlight (hours/day)

• Mean temperature (oC)

• Density of rose pollen produced (g/m2)

• Amount of pollen produced by each flower (g/flower)

The California newt, Taricha torosa, lives in the coastal areas around Los Angeles. Which of the following is a valid null hypothesis relating fitness to survival of a bottleneck event in a coastal area where a small, isolated population of California newts resides?

• Only those salamanders with the lowest evolutionary fitness will be eliminated by the bottleneck effect, lowering the allelic frequencies of their traits.

• Only those salamanders with the highest evolutionary fitness will survive the bottleneck event, raising the allelic frequencies of their traits.

• Surviving the bottleneck event will be random, so any change in the allelic frequencies of the salamander population is not attributed to fitness.

• Surviving the bottleneck event will be random, so there will be no changes to the allelic frequencies due to the bottleneck event.