Biologist know that some marine algae can create clouds by producing the gas dimethylsulphide (DMS), which reacts with oxygen in air above the sea to form solid particles. These particles provide a surface on which water vapor can condense to form clouds. Lovelock contends that this process is part of global climatic-control system. According to Lovelock, Earth acts like a super organism, with all its biological and physical systems cooperating to keep it healthy. He hypothesized that warmer conditions increase algal activity and DMS output, seeding more clouds, which cool the planet by blocking out the Sun. Then, as the climate cools, algal activity and DMS level decrease and the cycle continues. In response to biologists who question how organisms presumably working for their own selfish ends could have evolved to behave in a way that benefits not only the planet but the organisms as well, cooling benefits the algae, which remain at the ocean surface, because it allows the cooled upper layers of the ocean to sink, and then the circulating water carries nutrients upward from the depths below. Algae may also benefit from nitrogen raining down from clouds they have helped to form.
1. According to the passage, which of the following occurs as a result of cooling in the upper layers of the ocean?
A. The concentration of oxygen in the air above the ocean’s surface decreases.B. The concentration of DMS in the air above the ocean’s surface increases.
C. The nutrient supply at the surface of the ocean is replenished.
D. Cloud formation increases over the ocean.
E. Marine algae make more efficient use of nutrients.
2. Which of the following is most similar to the role played by marine algae in the global climate control system proposed by Lovelock?
A. A fan that continually replaces stale air in a room with fresh air from outside.B. A thermostat that automatically controls an air-conditioning system.
C. An insulating blanket that retains heat.
D. A filter used to purify water.
E. A dehumidifier that constantly removes moisture from the air in a room.
3. The
passage mentions the possible benefit to algae of nitrogen falling down in the
rain most likely in order to
A. provide support
for Lovelock’s response to an objection mentioned in the passageB. suggest that the climatic effects of DMS production have been underestimated
C. acknowledge that Lovelock’s hypothesis is based in part on speculation
D. demonstrate that DMS production alters the planet in more than one way
E. assert that algae are the sole beneficiaries of DMS production
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