Test 2 KEY -- BIOL 103, 2008
1.
(10 pts) Explain two different biological adaptations by which
an animal can protect itself from the desert heat. Many examples:
2. (15 pts) All ecosystems must cycle elements. A. Outline the fundamental cycle of carbon, hydrogen, and oxygen in Earth’s biosphere. Include key molecules; producers; and consumers.
Photosynthesis uses solar energy to split water, producing oxygen gas. The hydrogens are added to carbon dioxide (CO2 fixation) to build biomass (sugars, proteins, etc.). Consumers then break down biomass by oxidation, a process that spends energy.
B. Explain why the cycle would not work on Dune.
On Dune, the sandworms are supposed to generate oxygen (O2) through microbial fermentation in their digestive system (along with acids and aldehydes). However, there is no explanation of where the energy comes from to release oxygen gas, a high-energy compound. On Earth, only photosynthesis (by bacteria and plants) releases oxygen. There are not enough plants on Dune.
3. (10 pts) The Fremen store thousands of dekaliters of water underground on Dune. A. In the closed caverns underground, the temperature is 50º Fahrenheit. The water evaporates until saturation. What is the relative humidity? What percent of the air is water vapor?
If
the air is saturated with water, the relative humididy is 100%.
B.
Suppose some of the air escapes above ground, where it is trapped in
a tent. The temperature inside the tent rises to 90º Fahrenheit. If
the water percent of air remains the same, what is the relative humidity?
4. (10 pts)
Sharers hold their breath underwater:
B. For the breathmicrobes to help the Sharers hold their breath longer, what kind of protein must the breathmicrobes have? What key property would the protein have, compared to hemoglobin?
The breathmicrobes must have a protein similar to myoglobin, in that it retains oxygen at pressures lower than hemoglobin; that is, when hemoglobin has given up all its oxygen, the breathmicrobe protein would still have some left to provide. The protein presumably is purple when oxygenated, but turns white as it releases oxygen.
5. (20 pts) Both Fremen and Sharers adapt to an “extreme” environment.
A. Compare and contrast the Fremen and Sharer adaptations. Which adaptations are genetic, and which are cultural? Which adaptations involve cooperation with other life forms?
Many answers:
Fremen have few genetic adaptations; that is why Paul and Jessica can so readily adapt to their ways, which are cultural. It might be expected that Fremen would have evolved increased dehydration tolerance and down-pointing noses that avoid sand, but this is not described. On the other hand, Sharers have extensive genetic adaptations, including webbed feet and fingers, and inner eyelids. Nevertheless, the Sharers are as "human" as Valans; they can interbreed.
Fremen have cultural adaptations that serve to conserve water, such as the stillsuit, and traditions of saving all traces of water, which are shared among the tribe members. When people die, their water is immediately conserved for the tribe. Sharers have plenty of water, but limited living space; and the ocean has scarce nutrients, because of lack of access to minerals. Thus, Sharers must limit their population by the regulation of their own fertility, and through tight cooperative social systems that enforce this regulation. Both Sharers and Fremen have highly cohesive social structures that limit individual freedoms--but promote freedom of the group from oppression by outsiders.
Fremen cooperate with sandworms to maintain the spice flow and provide transport and defense against outsiders. Sharers cooperate with breathmicrobes for oxygen; with rocket squid and starworms for transport; with seaswallowers for maintaining a steady raft population; and with clickflies for communication.
B. How do the Fremen and the Sharers use their adaptations to resist foreign invasion?
The Fremen use their stillsuits and the sandworms to travel in parts of the desert where the invaders cannot go. Their desert survival skills also enhance their fighting ability. The Sharers use their superior swimming abilities, and their knowledge of the ecosystem, to evade the soldiers. They also use their nonviolent cultural responses to undermine the soldiers' attempts to enforce authority. 6. (20 pts) Carbon dioxide is increasing in the ocean. A. When the carbon dioxide dissolved in the ocean reaches 927 micrograms/Kg, what is expected to be the ocean pH?
According to the graph, the ocean is expected to reach 927 micrograms/Kg of carbon dioxide by the year 2100. At this point, the carbon dioxide converting to carbonic acid will lead to a pH of pH 7.85.
B. Calculate the concentration of hydrogen ions in the ocean today (2005), and the concentration of hydrogen ions at the ocean pH determined for part (A). What trend do you see?
Today, at pH 8.06, the [H+] = 10^-8.06 = 8.71 x 10-9 Molar (moles/liter). At
pH 7.85, it will be [H+] = 10^-7.85 = 1.41 x 10-8
Molar (moles/liter).
C. In Jurassic Park, explain how Dr. Grant cleans fossil bones.
Grant uses a weak acid (vinegar, acetic acid) to dissolve the limestone (calcium carbonate) away from the fossilized bones. The reaction is similar to that by which acid dissolve the shells of coral and other marine life. He also uses a fine brush to remove particulate matter from the bones.
7. (15 pts) The plant species of the planet Ralinius (created by Brian Cannon for BIOL 103) were mapped by DNA sequence comparison. The following table shows the percent similarity for all pairs of plant species. Assuming that mutations accumulate at 0.5% per million years, draw a phylogenetic tree of these species.
Each time of divergence is calculated by dividing the difference in DNA sequence by the rate of divergence (0.5% per million years). (100%
- 94%) / 0.5%/million years = 12 million years
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