In the 17th century, scientists were just beginning to understand the circulatory system of the heart. The two following viewpoints are the two most popular theories of the day.

Scientist I The heart pumps blood through arteries and veins but the two systems are separate. They are similar, just as the senses of smell and taste are when observing food, but ultimately they are two separate systems which perform separate functions. Hot blood flows from the heart, through the arteries, and to the organs which consume the blood much as a human would consume nourishment to survive. Venous blood originates in the liver and follows the veins to the organs where it is similarly consumed.

Scientist II The arteries and veins are two parts of one system. Blood flows from the heart, around the body, and back into the heart through the veins like two sets of one way streets. The idea of two systems, each pumping blood to the organs is unreasonable. If the heart can pump 6 oz of blood per minute, then the liver would have to produce 540 pounds of blood per day. A simple measurement of a human’s weight shows how unlikely that solution is. The single circulatory system is far superior as it explains the function of the heart, the arteries, and the veins clearly.

Why does Scientist I compare the arteries and veins to smell and taste?

Criminal and deviant acts have plagued society for many years. Scientists have tried to isolate variables and factors of individuals susceptible to these behaviors. The goal of this research is to create models of individuals most likely to commit deviant acts. Prediction of criminal behavior could reduce crime rates on a grand scale. Three scientists express their views on how to model criminal behavior and predict or prevent criminal acts.

Scientist 1

Criminal behavior is the result of prehistoric tendencies that favor aggressive and deviant acts for survival. A study of the corpses of criminals revealed that many exhibited prominent brows, strong upper bodies, large chests and other attributes that lend to a physical model of prediction that classifies criminals as "evolutionary throwbacks."

Scientist 2

Criminal behavior is the result of psychological ills that may be remedied with treatment and hospitalization. Studies have revealed that many criminal men possess an XYY makeup. This means that they contain one extra Y chromosome that results in aggressive, deviant, and criminal behaviors. Further studies have revealed that these genetic abnormalities can alter hormonal secretion and lead to criminally deviant actions and behaviors. Increased serotonin levels can lead to aggressive tendencies while altered dopamine secretion can chemically reward the commitment of deviant acts by stimulating pleasure receptors.

Scientist 3

Criminal behavior is the result of neurological abnormalities that can be studied and mapped. Studies of criminal and non-criminal persons have revealed inconsistencies in brain scans and neurological makeup. These alterations in brain chemistry and function have resulted in the development of sociopathic and narcissistic tendencies. These tendencies often increase probabilities for deviant and violent outbursts. The best way to predict criminal behavior is to utilize neurological scanning and mapping procedures.

A study of mice revealed that males possessing an XYY genotype are far more likely to engage in risky and aggressive behaviors. Which of the scientists would most agree with this evidence?

Sleep plays a vital role in defining the daily activities of virtually all animals. During periods of sleep, the parasympathetic nervous system becomes active and induces a relaxed state in response to increased levels of the hormone melatonin. Despite its ubiquity in the animal kingdom, the purpose of sleep and its role in our daily lives has been disputed by scientists. Two scientists discuss their theories about the purpose of sleep.

Scientist 1

During periods of sleep, animals are able to conserve energy that they would otherwise be spending on unnecessary activity. If an animal’s primary food source is most abundant during daylight, it is a waste of precious energy to be moving about at night. For example, many herbivores, such as squirrels, are diurnal (sleep during the night) because their food source is available during the day, while many insectivores, such as bats, are nocturnal (sleep during the day) because their food source is available during the night. Food sources, as an animal’s most valuable resource, dictate their sleep cycles. Many animal traits observable today evolved as a result of the supply and demand of food in their natural habitat.

Scientist 2

During waking hours, it is true that the body utilizes large amounts of energy; however, the role of sleep is to restore biological products that were utilized during periods of wakefulness, rather than simply to avoid utilizing energy in the first place. Many types of biological molecules, such as hormones, are released throughout the body while an animal is active. Sleep serves as a period of inactivity, during which the body can manufacture and store a supply of these molecules for future use during the next period of activity. Furthermore, sleep allows the body to repair cellular damages that has accumulated during waking hours. Experimental evidence shows that when animals are deprived of sleep, their immune system quickly weakens and death rates increase. Sleep is necessary for animals to prevent accumulation of damage and to regenerate crucial biomolecules for daily life.

Scientist 1’s theory would be most weakened if which of the following were true?

Sleep plays a vital role in defining the daily activities of virtually all animals. During periods of sleep, the parasympathetic nervous system becomes active and induces a relaxed state in response to increased levels of the hormone melatonin. Yet, despite its ubiquity in the animal kingdom, the purpose of sleep and its role in our daily lives has been disputed by scientists. Two scientists discuss their theories about the purpose of sleep.

Scientist 1

During periods of sleep, animals are able to conserve energy that they would otherwise be spending on unnecessary activity. If an animal’s primary food source is most abundant during daylight, it is a waste of precious energy to be moving about at night. For example, many herbivores, such as squirrels, are diurnal (sleep during the night) because their food source is available during the day, while many insectivores, such as bats, are nocturnal (sleep during the day) because their food source is available during the night. Food sources, as an animal’s most valuable resource, dictate their sleep cycles. Many animal traits observable today evolved as a result of the supply and demand of food in their natural habitat.

Scientist 2

During waking hours, it is true that the body utilizes large amounts of energy. However, the role of sleep is to restore biological products that were utilized during periods of wakefulness, rather than simply avoid utilizing energy in the first place. Many types of biological molecules, such as hormones, are released throughout the body while an animal is active. Sleep serves as a period of inactivity during which the body can manufacture and store a supply of these molecules for future use during the next period of activity. Furthermore, sleep allows the body to repair cellular damages that has accumulated during waking hours. Experimental evidence shows that when animals are deprived of sleep, their immune system quickly weakens and death rates increase. Sleep is necessary for animals to prevent accumulation of damage and to regenerate crucial biomolecules for daily life.

Which of the following best describes how the scientists view the role of sleep?

Sleep plays a vital role in defining the daily activities of virtually all animals. During periods of sleep, the parasympathetic nervous system becomes active and induces a relaxed state in response to increased levels of the hormone melatonin. Yet, despite its ubiquity in the animal kingdom, the purpose of sleep and its role in our daily lives has been disputed by scientists. Two scientists discuss their theories about the purpose of sleep.

Scientist 1

During periods of sleep, animals are able to conserve energy that they would otherwise be spending on unnecessary activity. If an animal’s primary food source is most abundant during daylight, it is a waste of precious energy to be moving about at night. For example, many herbivores, such as squirrels, are diurnal (sleep during the night) because their food source is available during the day, while many insectivores, such as bats, are nocturnal (sleep during the day) because their food source is available during the night. Food sources, as an animal’s most valuable resource, dictate their sleep cycles. Many animal traits observable today evolved as a result of the supply and demand of food in their natural habitat.

Scientist 2

During waking hours, it is true that the body utilizes large amounts of energy. However, the role of sleep is to restore biological products that were utilized during periods of wakefulness, rather than simply avoid utilizing energy in the first place. Many types of biological molecules, such as hormones, are released throughout the body while an animal is active. Sleep serves as a period of inactivity during which the body can manufacture and store a supply of these molecules for future use during the next period of activity. Furthermore, sleep allows the body to repair cellular damages that has accumulated during waking hours. Experimental evidence shows that when animals are deprived of sleep, their immune system quickly weakens and death rates increase. Sleep is necessary for animals to prevent accumulation of damage and to regenerate crucial biomolecules for daily life.

The scientists agree on which of the following principles:

Three doctors are discussing the most optimal way to approach cancer treatment. While they all acknowledge that cancer is uncontrolled cell proliferation, they have different opinions on whether chemotherapy is the best treatment method. Chemotherapy is the treatment of cancer with cytotoxic antienoplastic drugs. These drugs are used to kill fast-growing cancerous cells. All three doctors agree that chemotherapy has many associated side effects.

Doctor 1

While the drugs used for chemotherapy can be very strong, they need to be. Cancer, by its very definition, is made up of cells growing at a faster than normal rate. This means the treatment needs to be aggressive. The slower the effects of treatment, the more time the cancer has to spread; therefore, while the chemotherapy can also kill some healthy noncancerous cells in the process, it is still the best option.

Doctor 2

Chemotherapy does much more harm than good. Chemotherapy might temporarily destroy the cancer, but it does not cure the cancer. In addition, killing the cancerous cells means poisoning the body with chemicals and toxins. Instead, we should be addressing the reasons cancer exists in the first place, treating it at that step. Cancer is due to toxins in the body, industrial pollutions, and drugs. Avoiding sugar, exercising, and maintaining a healthy lifestyle—free of toxins, processed food, and other containments—is the best approach.

Doctor 3

Chemotherapy is effective in the sense that it kills the cancer cells. The downfall is that chemotherapy also kills the healthy cells in the process; therefore, we should be looking at way to decrease the amount of chemotherapy needed, so that we are only introducing the minimum amount of toxins into the body. Insulin Potentiating Therapy is a type of chemotherapy in which lower doses of chemotherapy are used because they are combined with insulin. Cancer cells have more insulin receptors than non-cancerous cells; therefore, cancer cells will have a biased absorption of such insulin-based chemotherapy when compared with noncancerous cells. In other words, piggybacking chemotherapy onto insulin allows cancer cells to absorb more of the chemotherapy, meaning less chemotherapy is needed and fewer noncancerous cells absorb the chemotherapy.

What is the argument behind Doctor 3's belief that the treatment he discusses is more effective—even though it uses a much lower dosage of chemotherapy?

Sleep plays a vital role in defining the daily activities of virtually all animals. During periods of sleep, the parasympathetic nervous system becomes active and induces a relaxed state in response to increased levels of the hormone melatonin. Despite its ubiquity in the animal kingdom, the purpose of sleep and its role in our daily lives has been disputed by scientists. Two scientists discuss their theories about the purpose of sleep.

Scientist 1

During periods of sleep, animals are able to conserve energy that they would otherwise be spending on unnecessary activity. If an animal’s primary food source is most abundant during daylight, it is a waste of precious energy to be moving about at night. For example, many herbivores, such as squirrels, are diurnal (sleep during the night) because their food source is available during the day, while many insectivores, such as bats, are nocturnal (sleep during the day) because their food source is available during the night. Food sources, as an animal’s most valuable resource, dictate their sleep cycles. Many animal traits observable today evolved as a result of the supply and demand of food in their natural habitat.

Scientist 2

During waking hours, it is true that the body utilizes large amounts of energy; however, the role of sleep is to restore biological products that were utilized during periods of wakefulness, rather than simply to avoid utilizing energy in the first place. Many types of biological molecules, such as hormones, are released throughout the body while an animal is active. Sleep serves as a period of inactivity, during which the body can manufacture and store a supply of these molecules for future use during the next period of activity. Furthermore, sleep allows the body to repair cellular damages that has accumulated during waking hours. Experimental evidence shows that when animals are deprived of sleep, their immune system quickly weakens and death rates increase. Sleep is necessary for animals to prevent accumulation of damage and to regenerate crucial biomolecules for daily life.

Scientist 2’s theory would be most weakened if which of the following were true?

Before modern technologies and experiments allowed scientists to understand different organisms' mechanisms of reproduction, numerous theories existed about how populations came to exist. Two scientists from the 1800s describe their theories. Here are their arguments.

Scientist I

Just like some plants come from seeds and others are capable of vegetative (asexual) reproduction, some animal organisms come from non-sexual reproduction as well. Maggots, for example, appear on rotting carcasses. It is clearly illogical to suggest that the dead animal created or gave birth to the maggots, as it is no longer alive and is therefore incapable of sexual reproduction. The only rational conclusion for the appearance of maggots is a spontaneous generation. This is similar to how, if one were to leave a bowl of broth in the open air for a week, it would turn cloudy from bacteria appearing in the liquid.

Scientist II

Animate objects cannot arise from inanimate objects. Even when plants perform asexual reproduction, daughter plants are still coming from parent plants. There is no other example in nature of a living organism spontaneously coming into being. It is true that we observe maggots on rotting carcasses, but that does not necessarily mean that the maggots came from the rotting carcass. Similarly, bacteria growing in broth do not necessarily come directly from the broth. If a living organism appears, then it must have come from another animate object, even if we did not witness it. It is more likely that these invisible organisms have come in through the air and we simply do not see them until they have had a chance to replicate in these locations.

If true, which of the following statements would disprove Scientist II's theory?

Ecological succession refers to the observable change of the species composition of an ecological community over a period of time. This phenomenon is also known as forest succession. It is a process that begins with the colonization of a habitat by robust pioneer species that can survive inclement and harsh environments. Pioneer species are characterized by small size and rapid reproduction of many offspring. Over successive generations these species are replaced with increasing complexity, until the ecosystem reaches a self-perpetuating climax community that ceases to vary in composition.

Several scientists express their views on the phenomenon of ecological succession.

Scientist 1

Ecological succession can be explained as primary succession. This theory suggests that forest evolution is the product of repeatable sequences of community changes known as seres. Each sere is predictable and deterministic to particular environmental circumstances. Scientists can therefore predict the changes in an environment with accuracy and precision based on observation.

Scientist 2

Ecological succession is not defined by predictable models. Chance plays a large role in creating ecological communities, whose species respond individualistically to environmental cues and pressures. These models are more complex in nature, and less simplified, than deterministic models. In these models, communities are regarded as products of the correlations between species distributions and environmental factors independent to each community.

According to Scientist 1, seres are best described by which of the following statements?

In the 17th century, scientists were just beginning to understand the circulatory system of the heart. The two following viewpoints are the two most popular theories of the day.

Scientist I The heart pumps blood through arteries and veins but the two systems are separate. They are similar, just as the senses of smell and taste are when observing food, but ultimately they are two separate systems which perform separate functions. Hot blood flows from the heart, through the arteries, and to the organs which consume the blood much as a human would consume nourishment to survive. Venous blood originates in the liver and follows the veins to the organs where it is similarly consumed.

Scientist II The arteries and veins are two parts of one system. Blood flows from the heart, around the body, and back into the heart through the veins like two sets of one way streets. The idea of two systems, each pumping blood to the organs is unreasonable. If the heart can pump 6 oz of blood per minute, then the liver would have to produce 540 pounds of blood per day. A simple measurement of a human’s weight shows how unlikely that solution is. The single circulatory system is far superior as it explains the function of the heart, the arteries, and the veins clearly.

How would Scientist I respond to Scientist II's claims that a human's weight disproves the theory that a liver pumps blood?