Problem: Pam and Alice studied Earth's climate and vegetation. Pam studied more about high latitudes (70 to 50N), while Alice studied about lower latitudes (30N to 20S). Which person studied more about alpine tundra? Hint: Alpine tundra occurs at high enough altitude at any latitude. Portions of montane grasslands and shrublands ecoregions worldwide include alpine tundra. Large regions of alpine tundra occur in the North American Cordillera, the Alps and Pyrenees of Europe, the Himalaya and Karakoram of Asia, the Andes of South America, and the Eastern Rift mountains of Africa.Alpine tundra occupies high-mountain summits, slopes, and ridges above timberline. Aspect plays a role as well; the treeline often occurs at higher elevations on warmer equator-facing slopes. Because the alpine zone is present only on mountains, much of the landscape is rugged and broken, with rocky, snowcapped peaks, cliffs, and talus slopes, but also contains areas of gently rolling to almost flat topography.Averaging over many locations and local microclimates, the treeline rises 75 metres (245 ft) when moving 1 degree south from 70 to 50N, and 130 metres (430 ft) per degree from 50 to 30N. Between 30N and 20S, the treeline is roughly constant, between 3,500 and 4,000 metres (11,500 and 13,100 ft).

A: Pam

Problem: Michael has become bored with his passive life style, and has decided to take up weight lifting as a hobby. He begins to exercise with weights several times a week. Michael's brother, Robert, isn't as motivated as Michael though. Robert decides to continue being mostly inactive and only exercises with weights every couple of months. Who will increase the size of their muscles less? Hint: In exercises such as weight lifting, skeletal muscle contracts against a resisting force (see Figure below ). Using skeletal muscle in this way increases its size and strength. In exercises such as running, the cardiac muscle contracts faster and the heart pumps more blood. Using cardiac muscle in this way increases its strength and efficiency. Continued exercise is necessary to maintain bigger, stronger muscles. If you don't use a muscle, it will get smaller and weakerso use it or lose it.

A: Robert

Problem: Two high school buddies, Dan and Bob, had very different lifestyles 30 years later. Dan made only healthy lifestyle choices, was vegan. Bob ate meat, cheese and didn't care about his health and didn't protect himself. Which man didn't lower the risk of cancer by avoiding carcinogens? Hint: Making these healthy lifestyle choices can also help prevent some types of cancer. In addition, you can lower the risk of cancer by avoiding carcinogens , which are substances that cause cancer. For example, you can reduce your risk of lung cancer by not smoking. You can reduce your risk of skin cancer by using sunscreen. How to choose a sunscreen that offers the most protection is explained below ( Figure below ). Some people think that tanning beds are a safe way to get a tan. This is a myth. Tanning beds expose the skin to UV radiation. Any exposure to UV radiation increases the risk of skin cancer. It doesn't matter whether the radiation comes from tanning lamps or the sun.

A: Bob

Problem: Ken and Stacy are two engineers discussing their plans about what source of energy they should use to generate electricity in a new city they are helping design. Ken feels that they should use coal since it's reliable, abundant and relatively cheap. Stacy argues that they should use solar power because there is an infinite supply of solar energy. Will Ken's plan send more or less gasses into the atmosphere than Stacy's plan? Hint: Another major cause of extinction is global warming , which is also known as global climate change. During the past century, the Earth's average temperature has risen by almost 1C (about 1.3F). You may not think that is significant, but to organisms that live in the wild and are constantly adapting to their environments, any climate change can be hazardous. Recall that burning fossil fuels releases gasses into the atmosphere that warm the Earth. Our increased use of fossil fuels, such as coal and oil, is changing the Earth's climate. Any long-term change in the climate can destroy the habitat of a species. Even a brief change in climate may be too stressful for an organism to survive. For example, if the seas increase in temperature, even briefly, it may be too warm for certain types of fish to reproduce.

A:
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