Summarize Argument: Phenomenon-Hypothesis
Scientists hypothesize male sage grouse inflate their air sacs during a courting ritual so that female sage grouse can select healthy mates. They provide no evidence for this claim.
Notable Assumptions
The scientists assume that inflated air sacs either signify health in themselves, or demonstrate some feature that signify health. They also assume female sage grouse can determine which males are healthy and which aren’t. Lastly, the scientists assume the female sage grouse are more likely to choose the healthy males.
A
Some female sage grouse mate with unhealthy male sage grouse.
This is irrelevant. Perhaps those were the only unhealthy male sage grouse left.
B
When diseased male sage grouse were treated with antibiotics, they were not selected by female sage grouse during the courtship ritual.
We have no idea what effect antibiotics have.
C
Some healthy male sage grouse do not inflate their air sacs as part of the courtship ritual.
Are those males chosen by the females? We would need to know in order for this to be a strengthener.
D
Male sage grouse are prone to parasitic infections that exhibit symptoms visible on the birds’ air sacs.
Females can note parasitic infections when male sage grouse inflate their air sacs. Thus, they are quite likely looking to see which males are healthy during the courting ritual.
E
The sage grouse is commonly afflicted with a strain of malaria that tends to change as the organism that causes it undergoes mutation.
This has nothing to do with air sacs.
Summary
Dinosaurs existed during the Mesozoic era. But no given species of dinosaur lived through the entire Mesozoic.
Dinosaurs lived only on land.
The Cretaceous period was at the end of the Mesozoic.
During the Cretaceous, the southern half of some region was covered by water.
Plesiosaurs were swimming reptiles that lived only during the Cretaceous.
Notable Valid Inferences
During the Cretaceous period, dinosaurs couldn’t have lived in the southern half of the region. (It was covered by water, and dinosaurs lived only on land.)
This is a Must Be False question, so any answer choice that contradicts this inference must be false.
A
Dinosaurs inhabited the northern half of the region throughout the entire Mesozoic era.
Could be true. We can infer that dinosaurs didn’t inhabit the southern half, but we’re told nothing about the northern half. It’s possible dinosaurs inhabited that region. And although no single species lived throughout the Mesozoic, it’s possible that dinosaurs as a whole did.
B
Plesiosaurs did not inhabit the southern half of the region during the Cretaceous period.
Could be true. We know plesiosaurs lived during the Cretaceous and were swimming reptiles, but we don’t know where they lived. Although the southern half of the region was covered by water, nothing suggests that plesiosaurs had to live there. They might have all lived elsewhere.
C
Plesiosaurs did not inhabit the southern half of the region before the Cretaceous period.
Must be true. Plesiosaurs lived only during the Cretaceous period, not before.
D
Dinosaurs did not inhabit the northern half of the region during the Cretaceous period.
Could be true. We don’t know anything about the northern half of the region, or where dinosaurs lived. It’s possible they all lived in other regions entirely.
E
Dinosaurs inhabited the southern half of the region throughout the entire Mesozoic era.
Must be false. The Mesozoic era includes the Cretaceous period, during which time the southern half of the region was covered entirely by water. Dinosaurs lived only on land. So dinosaurs could not have lived in the southern half of the region during that time.
Summary
The argument concludes that the dwarf masked owl will reside on the Baja peninsula this winter only if steps are taken to bring back spiny cacti. This is supported by the claims that spiny cacti provide the only suitable nesting sites for this owl on the Baja peninsula, and that a recent blight destroyed all of the peninsula’s spiny cacti.
Notable Assumptions
The conclusion that taking steps to reestablish spiny cacti is necessary for the owls to reside on the Baja peninsula over the winter involves several assumptions:
- That spiny cacti will not reestablish themselves on the Baja peninsula before winter even if no steps are taken.
- That there are no other plants which could be introduced to substitute for spiny cacti.
- That suitable nesting sites are necessary for the owls to reside on the Baja peninsula over the winter.
- That spiny cacti will not reestablish themselves on the Baja peninsula before winter even if no steps are taken.
- That there are no other plants which could be introduced to substitute for spiny cacti.
- That suitable nesting sites are necessary for the owls to reside on the Baja peninsula over the winter.
A
No birds of prey other than the dwarf masked owl nest in the spiny cactus.
The impact of the cactus blight on other birds is irrelevant to this argument, which is purely about the impact on the dwarf masked owl.
B
If the Baja peninsula contains spiny cacti, then the dwarf masked owl makes its winter home there.
Posing spiny cacti as a sufficient condition for the owl to reside on the peninsula over winter doesn’t contribute to the conclusion that reestablishing cacti is a necessary condition. Like (D), this is unnecessary.
C
On occasion the dwarf masked owl has been known to make its winter home far from its normal migratory route.
Whether this owl has previously spent the winter elsewhere doesn’t affect whether reestablishing the spiny cactus is necessary for the owl to spend this winter on the peninsula.
D
The dwarf masked owl will not make its winter home on the Baja peninsula only if that region contains no spiny cacti.
Like (B), this makes spiny cacti a sufficient condition for the owl to spend winter on the peninsula. This isn’t necessary for the argument, which poses reestablishing the cacti as a necessary condition.
E
Suitable nesting sites must be present where the dwarf masked owl makes its winter home.
The argument concludes that reestablishing spiny cacti is necessary on the basis that they exclusively provide nesting sites for the owl. Without this assumption, that link of support would be broken and the conclusion would be unsupported.