Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that the arrival of humans on Tiliga caused a decrease in the population and diversity of the island’s bird population. As support for this hypothesis, the author compares the top 50 cm of soil (which was accumulated over the 3,000 years since humans arrived) with the lower 150 cm of soil (which was accumulated over the previous 80,000 years). This comparison showed that before humans arrived, there was a larger and more diverse bird population.
Notable Assumptions
The author assumes that it was the arrival of the humans, not something else, that caused the decline in the population and diversity of birds. It could be that some thing else led to both the arrival of the humans and the decline in the bird population. We have a correlation between the arrival of humans and decline of birds, and the author is assuming a causal connection.
A
The bird species known to have been eaten by the islanders had few natural predators on Tiliga.
This reduces the strength of an alternate hypothesis (the alternate hypothesis being that predators may have been responsible for the declining bird population). Reducing the strength of alternate hypotheses is a way to strengthen arguments, so this does not weaken the argument.
B
Many of the bird species that disappeared from Tiliga did not disappear from other, similar, uninhabited islands until much later.
(B) says that birds disappeared much more slowly without humans. “Many” is too vague to make any strong inferences here, but this does give some reason to believe that the presence of humans is related to faster disappearance of birds, which is consistent with the argument.
C
The arrival of a species of microbe, carried by some birds but deadly to many others, immediately preceded the first human immigration to Tiliga.
This weakens the argument because it introduces an alternate hypothesis. (C) suggests that a microbe that arrived at the same time as humans could be responsible for the disappearance of the birds.
D
Bones from bird species known to have been eaten by the islanders were found in the underlying 150 centimeters of soil.
The birds that humans ate would have already existed (and died) on the island so it makes sense that their bones were found in the lower 150 cm of soil. This is consistent with the argument and doesn’t weaken the claim that humans caused a decrease in the bird population.
E
The birds that lived on Tiliga prior to the first human immigration generally did not fly well.
Information about birds’ abilities to fly is completely irrelevant to the argument.
"Surprising" Phenomenon
Why are mixed-age classrooms effective today, even though they were ineffective in the past?
Objective
The correct answer should tell us something that is different about mixed-age classrooms today compared to the past that would positively impact children’s ability to learn.
A
On average, mixed-age classrooms today are somewhat larger in enrollment than were the ones of the past.
We have no evidence that larger enrollment is better for learning. In fact, larger classes suggest that students might get less attention, which could make it harder for children to learn.
B
Mixed-age classrooms of the past were better equipped than are those of today.
This is something negative about today’s mixed-age classrooms compared to the past. So, it’s not going to help explain why mixed-age classrooms today achieve better results.
C
Today’s mixed-age classrooms, unlike those of the past, emphasize group projects that are engaging to students of different ages.
This is something positive about today’s mixed-age classes compared to the past. More engaging projects might lead to less boredom for older students and more attention given to younger students. This is the only answer that says something remotely positive about today’s classes.
D
Today’s mixed-age classrooms have students of a greater range of ages than did those of the past.
We don’t know whether having a greater range of ages is a positive development for learning. There’s evidence it isn’t, because past results show older students were bored, and younger students were confused. Increasing the age disparity in class might hurt learning.
E
Few of the teachers who are reviving mixed-age classrooms today were students in mixed-age classrooms when they were young.
This says most teachers of mixed-age classes today are not students in mixed-age classes when they were young. This doesn’t tell me something positive about mixed-age classrooms today compared to the past.
Cardiologist: Coronary bypass surgery is commonly performed on patients suffering from coronary artery disease when certain other therapies would be as effective. Besides being relatively inexpensive, these other therapies pose less risk to the patient since they are less intrusive. Bypass surgery is especially debatable for single-vessel disease.
Summary
Coronary bypass surgery is performed on patients with coronary artery disease when other treatments would be as effective. The other therapies are less expensive and pose less risk to the patient. These concerns are especially high for single-vessel disease.
Strongly Supported Conclusions
It is likely that therapies other than coronary bypass surgery would be as effective for conditions like single-vessel disease while posing less risk and cost to the patient.
A
Bypass surgery is riskier than all alternative therapies.
This is unsupported because the author only states that there are some therapies with less risk than coronary bypass surgery, not that all therapies are less risky. There could be other therapies with much greater risk that are not discussed.
B
Needless bypass surgery is more common today than previously.
This is unsupported because the author provides no information about the frequency of different surgeries over time.
C
Bypass surgery should be performed when more than one vessel is diseased.
This is unsupported because although the author said bypass surgery is especially debatable for single-vessel disease, the author leaves open the possibility that bypass surgery is also too risky for diseases of multiple vessels.
D
Bypass surgery is an especially expensive therapy when used to treat single-vessel disease.
This is unsupported because while we know that bypass surgery is especially debatable for single-vessel disease, we don’t know if this is due to cost or risk.
E
Sometimes there are equally effective alternatives to bypass surgery that involve less risk.
This is strongly supported because the stimulus indicates that other therapies are as effective as bypass surgeries and that these therapies involve lower risk.
Summarize Argument: Phenomenon-Hypothesis
The author puts forward a theory that tidal ranges — the difference between a tide’s highest and lowest points — must be explained by gravitational forces since those kinds of forces are the tides’ only cause.
Identify and Describe Flaw
The argument fails to consider that while an event may have just one cause, it can still be affected by other forces. There could be many factors such as geography, weather, etc. that all impact how high or low a tide rises or falls. Even though these factors don’t directly cause the tides to occur, they can certainly exert some kind of influence on their ranges.
A
It gives only one example of a tidal range.
This isn’t a flaw. The Bay of Fundy is given as one example of a tidal range, but the argument’s logic would be the same whether it gave more examples or no examples at all.
B
It fails to consider that the size of a tidal range could be affected by the conditions in which gravitational forces act.
This describes how other factors could affect tidal ranges without being the cause of the tides themselves. For example, a rainstorm might cause the water level to be higher even though rain isn’t what causes the tide itself.
C
It does not consider the possibility that low tides are measured in a different way than are high tides.
This is irrelevant. There’s no reason to think that they’d be measured differently. Even if they were, the argument’s logic would be the same.
D
It presumes, without providing warrant, that most activity within the world’s oceans is a result of an interplay of gravitational forces.
The argument simply doesn’t do this. The argument says that gravity causes tides, but never mentions any other activities in the ocean.
E
It does not differentiate between the tidal effect of the sun and the tidal effect of the moon.
This is an irrelevant distinction. The argument claims that only gravitational force affects tidal ranges. This point could still stand whether that force came from the sun or the moon.
Summary
Before 1985, all commercial airlines replaced the cabin air in a plane once every 30 minutes. After 1985, airlines replace the cabin air once every hour. The less frequently cabin air is replaced, the higher the level of carbon dioxide in the cabin air and the easier it is for airborne illnesses to spread.
Strongly Supported Conclusions
Modern airplanes have higher levels of carbon dioxide in the cabin air compared to planes before 1985.
A
In 1985 there was a loosening of regulations concerning cabin air in commercial airline flights.
This answer is unsupported. We don’t know from the stimulus what caused commercial airlines to replace the rate of replacement from every 30 minutes to every hour.
B
People who fly today are more likely to contract airborne illnesses than were people who flew prior to 1985.
This answer is unsupported. The stimulus is limited to what is true of commercial airlines. For this answer, you have to assume that people who fly today fly on commercial airlines.
C
Low levels of carbon dioxide in cabin air make it impossible for airborne illnesses to spread.
This answer is unsupported. “Impossible” is too strong in this answer. We only know from the stimulus that higher levels of carbon dioxide can make it easier for airborne illness to spread.
D
In 1980 the rate at which the cabin air was replenished in commercial airliners was sufficient to protect passengers from the effects of carbon dioxide buildup.
This answer is unsupported. We don’t know from the stimulus what the effects of carbon dioxide buildup are.
E
In 1980 the level of carbon dioxide in the cabin air on a two-hour commercial airline flight was lower than it is today on a similar flight.
This answer is strongly supported. Since cabin air would have been replaced every 30 minutes during a flight in 1980, that flight would have lower levels of carbon dioxide compared to a similar modern flight.
The passages doesn't mention this but... Levi-Montalcini was a Jew living under Fascist Italy. As a consequence, she was fired from her university and had to go into hiding. The Nobel research you just read about she did in a makeshift lab she set up in the room where she slept while hiding from murderous fascists.
Please join me as I bow down in eternal respect.