1) Climate change is probably the most serious threat to human existence on Planet Earth. The main cause of climate change is global warming. First, indicate the one molecule that alone is most responsible for the earth’s warming. Second, describe at least two possible approaches to reducing the abundance of this molecule in the atmosphere.

2) Each day on your walk along a pathway near a wooded lot, you notice one of the plants you pass has yellow leaves. At first you think the plant is senescent (dying of old age), but over the course of several days you notice that the plant is not dying, but rather it’s growing rapidly. You know plants grow because they photosynthesize, and that photosynthesis requires chlorophyll, which is green, not yellow. How do you explain this plant’s rapid growth?

3) Genomic variation is required, not only for evolution to proceed, but also as an aid for experimental analysis of biological systems, and for therapeutic purposes. For these reasons, it is important to have the capacity to induce mutations in genomes of living things. In a few words, describe how mutations have been acquired in the past. Then indicate the most effective way it is done currently.

4) Lions are obligate carnivores, i.e., they do not eat plants. Do you think a case can be made that the existence of lions depends on the vegetation of their habitat? Describe the reason for the answer you chose.

5) Lactate (lactic acid) is converted to pyruvate by an enzyme called lactate dehydrogenase. Certain plants produce a molecule (let’s call it Inhibitor 1) that inhibits activity of lactate dehydrogenase. When cows eat these plants, Inhibitor 1 is concentrated in their milk. If humans drink milk from these cows they become sick with abdominal pain and vomiting. If these sick people engage in vigorous exercise, their symptoms become worse. Explain why this happens.

6) Conversion of substrate to product can occur spontaneously, but this process is slow, not fast enough to sustain life. Reactions mediated by enzymes are much faster, and involve the “Lock-and-Key” model of how shapes of specific enzymes fit with shapes of specific substrates. After fitting the shapes together, the next step is to lower the activation energy of the reaction. Describe how the enzyme can treat the substrate in order to do this.