I read this background article the other day: Plants called epiphytes grow on other plants. They obtain moisture from the air and make food by photosynthesis. Most epiphytes are ferns or orchids that live in tropical or temperate rainforests (see Figure below ). Host trees provide support, allowing epiphyte plants to obtain air and sunlight high above the forest floor. Being elevated above the ground lets epiphytes get out of the shadows on the forest floor so they can get enough sunlight for photosynthesis. Being elevated may also reduce the risk of being eaten by herbivores and increase the chance of pollination by wind.  I am facing a new situation today: While hiking Bob likes to collect plant specimens. Yesterday, he was hiking along a creek, and was specifically looking for epiphytes. Eventually, he found one, and tagged the specimen as specimen A. To compare specimen A with another plant he collected another plant specimen that was not an epiphyte. He tagged that specimen as specimen B.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Would specimen A grow above the ground or on the ground?
Ans: above the ground

I read this background article the other day: Ocean acidification occurs when excess carbon dioxide in the atmosphere causes the oceans to become acidic. Burning fossil fuels has led to an increase in carbon dioxide in the atmosphere. This carbon dioxide is then absorbed by the oceans, which lowers the pH of the water. Ocean acidification can kill corals and shellfish. It may also cause marine organisms to reproduce less, which could harm other organisms in the food chain. As a result, there also may be fewer marine organisms for humans to consume.  I am facing a new situation today: The biologists found out that the Indian Ocean had a lower water pH than it did a decade ago, and it became acidic. The water in the Arctic ocean still had a neutral to basic pH.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which ocean has a lower content of carbon dioxide in its waters?
Ans: Arctic

I read this background article the other day: Machines make work easier by increasing the amount of force that is applied, increasing the distance over which the force is applied, or changing the direction in which the force is applied. Contrary to popular belief, machines do not increase the amount of work that is done. They just change how the work is done. So if a machine increases the force applied, it must apply the force over a shorter distance. Similarly, if a machine increases the distance over which the force is applied, it must apply less force.  I am facing a new situation today: Archimedes was a great scientist. He was also a great inventor of machines. He once said that if he could stand somewhere, he could move the earth with his machine. Hearing that, king of Sicily called Archimedes and his fellow scientist Ptolemy to come up with great inventions. Archimedes, as everyone expected, came up with a great machine. But Ptolemy couldn't do much in such a limited time. So, his device was not a machine.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Would Ptolemy's device more likely or less likely make work easier than Archimedes' one?
Ans: less likely

I read this background article the other day: Protozoa generally feed by engulfing and digesting other organisms. As consumers, they have various roles in food chains and webs. Some are predators. They prey upon other single-celled organisms, such as bacteria. In fact, protozoa predators keep many bacterial populations under control. Other protozoa are herbivores. They graze on algae. Still others are decomposers. They consume dead organic matter. There are also parasitic protozoa that live in or on living hosts. For example, the protozoan that causes malaria lives inside a human host. Protozoa are also important food sources for many larger organisms, including insects and worms.  I am facing a new situation today: The students studied two ponds. Class A studied a pond filled with protozoa, while class B studied a pond with almost no protozoa.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which class observed more engulfing and digesting of other organisms?
