1. Biologists have classified the elephant shrew, a small mole-like mammal, with other shrews of similar size and body shape. However, this classification has been questioned, since elephant shrews have much more well-developed eyes and ears than other animals in the shrew family and use their tongues like anteaters to feed on insects, a trait not shared with true shrews. Because of their similarities to anteaters, a biologist has proposed that the elephant shrew is more closely related to anteaters than to shrews. Design a plan for investigating the validity of this new hypothesis. Describe your plan and include the methods and sources of material you would need to carry out your plan. (3 points) 2. Researchers have concluded that all organisms share a common ancestor. Explain two characteristics of cells that support this conclusion. (3 points)

3. Analyze the data shown in the three graphs below. Use the data to compare the mechanism of extinction and the change in species diversity in the history of Cambrian and Paleozoic fauna (animals). (2 points)

4. Scientists have proposed that speciation occurs when members of a population become reproductively isolated from one another. For example, speciation can occur when a population becomes split by a physical barrier and the two populations come under different selection pressures. Recently, fossils of fish have been discovered in sediments on opposite coasts of a large island that arose following a volcanic eruption event. Design an experiment to test the hypothesis that speciation occurred in these fish. Include a description of your experimental plan, the types of data you will collect, and an explanation of how the data will enable you to determine whether the hypothesis is correct. (2 points)

5. Stanley Miller and Harold Urey performed an experiment in 1953 in which they attempted to reproduce conditions present on early Earth long before any life was present.

a. What hypothesis were they testing? (1 points)

b. Following this experiment, it was discovered that volcanoes produce mainly water vapor and carbon dioxide, not ammonia and methane as Miller and Urey had assumed. Explain how this evidence led to problems with the conclusions drawn from the results of their experiment. (2 points)

6. Alternative models have suggested hydrothermal vents in the deep ocean or other planets as possible sites for life’s origins.

a. Evaluate whether either or both of these two models are testable, and explain your reasoning. (2 points)

b. Evaluate whether the hydrothermal vent model would have to be modified if it is found that the materials emerging from hydrothermal vents likely did not contain the element carbon four billion years ago. (1 points)

c. Suppose you became aware of a report in a scientific journal that amino acids had been found in a meteorite by university researchers. At about the same time, a meteorite hunter has been profiled in the news for having found a meteorite with evidence of fossils from shelled organisms. Evaluate these two pieces of evidence in terms of how they might support a model for the origin of life on Earth. (1 points)

7. The following graph shows the concentrations of various gases making up Earth’s atmosphere in its early history. Explain how a chemical analysis of the elements present in minerals taken from rocks dating to 4 billion years ago would have provided evidence that helped create this graph. In particular, explain how evidence from rocks demonstrated a lack of oxygen in the atmosphere at the earliest stages of Earth’s history. (4 points)

8. Explain how the following experiment provided support for the claim that DNA is the primary source of heritable information. (4 points)

Two experiments are run side by side:

1. One set of virus particles is labeled with the sulfur-35 isotope. A second set is labeled with phosphorus-32 isotope.

2. Each set of labeled virus particles is incubated with different batches of the same bacteria.

3. Following infection of the bacteria by the virus particles, the bacteria are separated from the virus particles by agitation in a blender.

4. The bacterial cells are separated from the virus particles by centrifugation.

5. The supernatant and pellet (two separated components) from each batch are analyzed to determine the locations of the isotope labels.

Results:

1. Radioactive sulfur is found in the supernatant.

2. Radioactive phosphorus is found in the cell pellet.

3. A new generation of viable virus particles emerge from the bacteria cells when they are reconstituted in liquid culture.