A group of scientists wanted to test the effects of Nitra-Grow, a chemical additive that can be given to plants to help them grow. 3 test groups of plants were given all the same time of sunlight, the same type of soil, and the same amount of water. Plant A was given no extra chemicals. Plant B was given 5g of Nitra-Grow. Plant C was given 5g of Ammonia to see if Nitra-Grow worked any better than a basic nitrogen-based household product. The plants are then measured on 5 consecutive days to find their average height (in cm).

What is the general relationship between plant height and the amount of days?

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.

Both scientists give evidence to support their theories. The evidence given by Scientist 1 can best be described as __________.

The chart above shows the height growth of three different plant species after a period of 2 weeks. Each plant species was grown in 4 different soil mediums. All the plants were grown in the same environment with equal amounts of light, water, and oxygen.

Based on the chart above, which plant species was consistently taller than the other plant species regardless of soil medium?

The chart above shows the height growth of three different plant species after a period of 2 weeks. Each plant species was grown in 4 different soil mediums. All the plants were grown in the same environment with equal amounts of light, water, and oxygen.

Which soil medium provides the tallest plant growth?

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.

Both scientists give evidence to support their theories. The evidence given by Scientist 2 can best be described as __________.

Bacterial resistance is a common issue encountered in various infections. Scientists have attributed this phenomenon to the overuse of anti-bacterial sanitizers and prescription antibiotics. Two groups of researchers performed studies to test bacterial resistance.

Study 1

Researchers in this study state that bacterial resistance is the result of bacterial plasmid translocation. Bacteria carry their genes on circular rings of bacterial DNA and on small, physically separate molecules known as plasmids. Plasmids are unique because they are replicons that are capable of replication autonomously within a suitable host. Researchers radioactively marked plasmids in bacterial specimens and noted that they could be easily transmitted from one bacterium to another via horizontal gene transfer. They then observed that the genes transferred from the plasmid could be incorporated into the bacteria’s genetic makeup. These genetic alterations enhanced survivorship within the environment and promoted resistance to antibiotics. They concluded that plasmids carry genes important for survival and facilitate bacterial resistance to antibiotics.

Study 2

Researchers in this study state that resistance is the result of the misuse of antibiotics. Researchers administered various antibiotics to a culture of E. coli and studied their effects over time (Figure 1). They concluded that bacterial resistance is the result of natural selection. In other words, the strongest bacteria survive antibiotics and reproduce, which produces anitbiotic-resistant offspring bacteria.

Figure 1

In Study 2, what was the general trend in bacterial population for the bacteria exposed to ampicillin?

Bacterial resistance is a common issue encountered in various infections. Scientists have attributed this phenomenon to the overuse of anti-bacterial sanitizers and prescription antibiotics. Two groups of researchers performed studies to test bacterial resistance.

Study 1

Researchers in this study state that bacterial resistance is the result of bacterial plasmid translocation. Bacteria carry their genes on circular rings of bacterial DNA and on small, physically separate molecules known as plasmids. Plasmids are unique because they are replicons that are capable of replication autonomously within a suitable host. Researchers radioactively marked plasmids in bacterial specimens and noted that they could be easily transmitted from one bacterium to another via horizontal gene transfer. They then observed that the genes transferred from the plasmid could be incorporated into the bacteria’s genetic makeup. These genetic alterations enhanced survivorship within the environment and promoted resistance to antibiotics. They concluded that plasmids carry genes important for survival and facilitate bacterial resistance to antibiotics.

Study 2

Researchers in this study state that resistance is the result of the misuse of antibiotics. Researchers administered various antibiotics to a culture of E. coli and studied their effects over time (Figure 1). They concluded that bacterial resistance is the result of natural selection. In other words, the strongest bacteria survive antibiotics and reproduce, which produces anitbiotic-resistant offspring bacteria.

Figure 1

In Study 2, which bacterial culture developed resistance to the antibiotic it was administered over the 15-day trial?

Species competition is driven by a variety of factors. Resources such as water, food, sunlight, and suitable habitat are among the top contributors that influence interspecific and intraspecific competition. Interspecific is competition between different species and intraspecific competition is between members of the same species.

One interesting example of interspecific completion is that of two barnacle species that inhabit intertidal zones. Balanus balanoides inhabits the lower intertidal zone and Chthamalus stellatus inhabits the lower intertidal zone. A researcher attempts to study this phenomenon.

The researcher removes the Balanus species from the lower intertidal zone and observes that the Chthamalus species expands its range to inhabit the lower intertidal zone and the upper intertidal zone. The researcher then removes the Chthamalus species from the upper tidal zone of a different area and observes that the Balanus species does not extend its range. The researcher concludes that competition has allowed each species to exist simultaneously by forming specialized niches that promotes survivorship for each species.

Researchers suggest that the Balanus species disrupts the Chthamalus species' ability to inhabit the lower intertidal zones because it is much larger and can physically remove the smaller Chthamalus without much effort. Does this information agree witht the data observed in the barnacle study?

Bacterial resistance is a common issue encountered in various infections. Scientists have attributed this phenomenon to the overuse of anti-bacterial sanitizers and prescription antibiotics. Two groups of researchers performed studies to test bacterial resistance.

Study 1

Researchers in this study state that bacterial resistance is the result of bacterial plasmid translocation. Bacteria carry their genes on circular rings of bacterial DNA and on small, physically separate molecules known as plasmids. Plasmids are unique because they are replicons that are capable of replication autonomously within a suitable host. Researchers radioactively marked plasmids in bacterial specimens and noted that they could be easily transmitted from one bacterium to another via horizontal gene transfer. They then observed that the genes transferred from the plasmid could be incorporated into the bacteria’s genetic makeup. These genetic alterations enhanced survivorship within the environment and promoted resistance to antibiotics. They concluded that plasmids carry genes important for survival and facilitate bacterial resistance to antibiotics.

Study 2

Researchers in this study state that resistance is the result of the misuse of antibiotics. Researchers administered various antibiotics to a culture of E. coli and studied their effects over time (Figure 1). They concluded that bacterial resistance is the result of natural selection. In other words, the strongest bacteria survive antibiotics and reproduce, which produces anitbiotic-resistant offspring bacteria.

Figure 1

How many bacteria were present at the start of each trial in Study 2?

In the 1980’s, an epidemic of bovine spongiform encephalopathy, or mad cow disease, swept through cattle herds in the United Kingdom. Scientists and veterinarians were troubled and had a difficult time managing the disease because it spread from one animal to another, and behaved differently than other diseases in the past.

When infectious material from affected animals was treated with high levels of radiation, for example, the material remained infectious. All known bacteria or viruses that carry disease would have been killed by such a treatment. Additionally, some animals developed the disease without first being exposed to sick animals. Perhaps most frustratingly, among those animals that are exposed before becoming sick, it can take many years after exposure for illness to appear.

There quickly emerged two distinct explanations for the disease.

Scientist 1:

Mad cow disease is unlike any disease we have handled before. It is increasingly clear that the best explanation for the disease’s dynamics involve proteins, called the protein-only hypothesis. These protein molecules are likely causative of the disease, and they lack any DNA or RNA. It is damage to these DNA or RNA molecules that kills bacteria or viruses when exposed to high levels of radiation. The most important observations that made scientists consider a unique, protein-only model for this disease involved its resistance to radiation. Remarkably, this would be the first example of an infectious agent copying itself without DNA or RNA to mediate the process.

Moreover, some animals develop the disease spontaneously, without physically being infected by another animal. This suggests that internal disorder among protein molecules is a potential route to developing disease, and may be accelerated by exposure to other sick animals.

In fact, this is consistent with the proposed mechanism. It is likely that proteins fold incorrectly, and then influence proteins around them to take on this errant conformation. Some proteins may fold incorrectly by chance, which explains spontaneous disease development. It also explains the long course of disease, as it takes many years for enough proteins to fold incorrectly and result in observable disease.

Scientist 2:

The suggestion that mad cow disease is caused exclusively by protein, in the absence of DNA or RNA, is such a dramatic departure from accepted biological processes that it warrants careful scrutiny. Additionally, other more conventional explanations should be thoroughly investigated before coming to such a conclusion.

Some scientists have shown that very small particles resembling viruses are visible in infectious material under powerful microscopes. Additionally, these viruses are consistent in size and shape with known, highly radiation-resistant viruses called polyomaviruses. It takes much higher-than-typical doses of radiation to cause enough DNA damage to inactivate these viruses.

The observation that mad cow disease occurs spontaneously in some animals is also explained by the viral explanation. Many viruses exist in animals and humans for years, undetected and not causing any observable disease. Sickness or stress can make these viruses reactivate, offering the illusion of spontaneous illness. All of these observations are consistent with the viral hypothesis.

Which of the following would most directly refute the protein-only hypothesis?

I. It is found that more animals than previously thought develop the disease spontaneously, without exposure to infected material

II. Another disease is found to be caused by a protein lacking any DNA or RNA

III. Treatment with an enzyme that breaks down DNA and RNA makes infectious material non-infectious