Question: Predators play an important role in an ecosystem. For example, if they did not exist, then a single species could become dominant over others. Grazers on a grassland keep grass from growing out of control. Predators can be keystone species . These are species that can have a large effect on the balance of organisms in an ecosystem. For example, if all of the wolves are removed from a population, then the population of deer or rabbits may increase. If there are too many deer, then they may decrease the amount of plants or grasses in the ecosystem. Decreased levels of producers may then have a detrimental effect on the whole ecosystem. In this example, the wolves would be a keystone species. Karen studied animals in school. She started studying predators for a school presentation. She liked it. Her friend Molly liked cows, sheep and other herbivores, so she decided to do a presentation about grazers, and their role in nature. Which girl learned more about animals that keep grass from growing out of control?
Answer: Molly

Question: 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. Keith is a doctor at the city hospital. Today, he is seeing six patients, patient A, patient B, patient C, patient D, patient E, and patient F. Patient A is a smoker, but patient B is not a smoker. Patient C uses sunscreen, but patient D does not use any sunscreen. Patient E tans with tanning lamps, but patient F tans in the sun. Would patient B have higher or lower risk of lung cancer than patient A?
Answer: lower

Question: Sometimes muscles and tendons get injured when a person starts doing an activity before they have warmed up properly. A warm up is a slow increase in the intensity of a physical activity that prepares muscles for an activity. Warming up increases the blood flow to the muscles and increases the heart rate. Warmed-up muscles and tendons are less likely to get injured. For example, before running or playing soccer, a person might jog slowly to warm muscles and increase their heart rate. Even elite athletes need to warm up ( Figure below ). Beth and Sally are both on the high school basketball team and are about to play a match against their rival school. This match is extremely important, and students from both schools always turn out in droves to support their team. Last year, Beth and Sally's team lost so they are extra motivated this year to win. Before the game, Beth spends her time running in place and doing jumping jacks to prepare, and Sally spends her time talking to her friends who are sitting in the bleachers cheering the team on. Are Beth's muscles more or less ready for the game than Sally's?
Answer:
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