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In comparing the results of a recent annual spring census to those of the previous year, biologists observed dramatic changes in the numbers of frogs of two species—Species X and Species Y—and an overall decrease in the combined number of frogs of these species. The biologists hypothesized that this decrease was caused by the unusually cold weather between the two censuses.
Select for A and for B the statements such that the biologists' hypothesis would have the most support if A is true and B is false. Make only two selections, one in each column.
Species X is susceptible to unusually cold weather whereas Species Y is not.
Species X has a later mating season than does Species Y.
Both Species X and Species Y are susceptible to similar contaminants.
The number of Species X frogs decreased from the previous spring census.
The number of Species Y frogs decreased from the previous spring census.
| Text from Passage | Analysis |
|---|---|
| "biologists observed dramatic changes in the numbers of frogs of two species—Species X and Species Y" |
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| "an overall decrease in the combined number of frogs of these species" |
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| "The biologists hypothesized that this decrease was caused by the unusually cold weather" |
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We need to select statements where:
The combination of A being true and B being false must provide the most support for the hypothesis.
For the cold weather hypothesis to be strongly supported:
Specific prethinking:
Choice 1: "Species X is susceptible to unusually cold weather whereas Species Y is not."
Choice 2: "Species X has a later mating season than does Species Y."
Choice 3: "Both Species X and Species Y are susceptible to similar contaminants."
Choice 4: "The number of Species X frogs decreased from the previous spring census."
Choice 5: "The number of Species Y frogs decreased from the previous spring census."
For Part A: Choice 1 - "Species X is susceptible to unusually cold weather whereas Species Y is not."
For Part B: Choice 5 - "The number of Species Y frogs decreased from the previous spring census."
When A is true and B is false:
Choice 4 for A: While "X decreased" being true fits the observation, it doesn't explain WHY X decreased or support the cold weather hypothesis specifically.
Choice 3: Introducing contaminants creates an alternative explanation that would actually weaken support for the cold weather hypothesis.
Choice 2: Mating seasons might relate to cold exposure timing, but it's too indirect compared to direct susceptibility.