1. Answer three of the following five questions in a 3-4 page summary.
The integrity of the plasma membrane is essential for cellular survival. Could the immune system utilize this fact to destroy foreign cells that have invaded the body? How might cells of the immune system disrupt membranes of foreign cells? (Two hints: virtually all cells can secrete proteins, and some proteins form pores in membranes.)
Most cells are very small. What physical and metabolic constraints limit cell size? What problems would an enormous cell encounter? What adaptations might help a very large cell to survive?
When a brown bear eats a salmon, does the bear acquire all the energy contained in the body of the fish? Why or why not? What implications do you think this answer would have for the relative abundance (by weight) of predators and their prey? Does the second law of thermodynamics help explain the title of the book, Why Big Fierce Animals are Rare?
You are called before the Ways and Means Committee of the House of Representatives to explain why the U.S. Department of Agriculture should continue to fund photosynthesis research. How would you justify the expense of producing, by genetic engineering, the enzyme that catalyzes the reaction of RuBP with CO2 and prevents RuBP from reacting with oxygen as well as CO2? What are the potential applied benefits of this research?
Some species of bacteria that live at the surface of sediment on the bottom of lakes are facultative anaerobes; that is, they are capable of either aerobic or anaerobic respiration. How will their metabolism change during the summer when the deep water becomes anoxic (deoxygenated)? If the bacteria continue to grow at the same rate, will glycolysis increase, decrease, or remain the same after the lake becomes anoxic? Explain why.
2. The evolution of antibiotic resistance in bacterial populations is a direct consequence of natural selection applied by widespread use of antibiotic drugs. When a new antibiotic is first introduced, it kills the vast majority of bacteria exposed to it. The surviving bacterial cells, however, may include individuals whose genomes happen to include a mutant gene that confers resistance. As Darwin understood, individuals carrying the resistance gene will leave behind a disproportionately large share of offspring, which inherit the gene. If the environment consistently contains an antibiotic, bacteria carrying the resistance gene will eventually come to predominate. Because bacteria reproduce so rapidly and have comparatively high rates of mutation, evolutionary change leading to resistant populations is often rapid.
We have accelerated the pace of the evolution of antibiotic resistance by introducing massive quantities of antibiotics into the bacteria's environment. Each year, U.S. physicians prescribe more than 100 million courses of antibiotics; the Centers for Disease Control estimate that about half of these prescriptions are unnecessary. An additional 20 million pounds of antibiotics are fed to farm animals annually. The use of antibacterial soaps and cleansers has become routine in many households. As a result of this massive alteration of the bacterial environment, resistant bacteria are now found not only in hospitals and the bodies of sick people but are also widespread in our food supply and in the environment. Our heavy use (many would say overuse) of antibiotics means that susceptible bacteria are under constant attack and that resistant strains have little competition. In our fight against disease, we rashly overlooked some basic principles of evolutionary biology and are now paying a heavy price.