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Zorluk: OrtaStrengthen

Paleoecologist: Fossilized molars of late Pleistocene steppe bison reveal a pronounced decrease in microscopic enamel striations beginning roughly 20,000 years ago. Because abrasive silica phytoliths in steppe grasses cause heavy tooth wear, some researchers concluded that a severe drought forced the bison to alter their diet from rough grasses to softer shrubs. However, soil isotope samples from that period establish that grass abundance did not decline. Therefore, the decrease in striations was instead caused by deeper winter snowpack, which prevented the bison from grazing down to the soil-covered bases of the grass stems where gritty mineral dust accumulates.

Which of the following, if true, most strengthens the paleoecologist's argument?

  1. A
    During the late Pleistocene, winter snowpack in the steppe region formed a dense ice crust that frequently forced large herbivores to expend extra energy digging for forage.
  2. Contemporary bison grazing in areas with deep winter snowpack feed almost exclusively on the exposed upper blades of grasses and exhibit significantly less tooth enamel wear than bison grazing on the same grasses in snow-free areas.Cevap
  3. C
    No herbivore species native to the Pleistocene steppe ever incorporated tundra shrubs into its diet during seasons when grass was readily accessible.
  4. D
    Soil isotope analysis provides far more precise measurements of prehistoric plant distribution than does microscopic analysis of fossilized tooth wear.
  5. E
    Steppe grasses from 20,000 years ago produced substantially higher concentrations of abrasive silica phytoliths than did grasses from earlier periods.

Cevap

The argument is most strengthened by the finding that contemporary bison in deep snowpack feed only on upper grass blades and show significantly less tooth wear than bison eating identical grasses in snow-free areas.
The correct answer provides direct empirical support for the author's causal model by showing that when bison graze under deep snowpack, their feeding is restricted to the upper parts of the plants and results in significantly less tooth wear than when grazing on the same grasses without snow. This verifies that snowpack can indeed produce the reduction in striations observed in the fossil record.

Adım Adım Çözüm

1
Analyze the stimulus structure and identify the conclusion and evidence.
The author concludes that reduced dental striations were caused by deep snowpack preventing bison from eating gritty, soil-covered stem bases, relying on evidence that grasses remained abundant despite a drop in wear.
Isolating the specific causal hypothesis is required to determine what evidence would substantiate it.
2
Identify the unstated assumption and logical gap in the causal claim.
The argument assumes that grazing restricted to upper grass blades due to snow cover actually leads to a measurable reduction in dental wear compared to grazing in low-snow conditions.
Strengthening an argument requires finding a claim that validates the causal mechanism or rules out confounding factors.
3
Evaluate the answer choices to find the statement that substantiates this causal connection.
Evidence demonstrating that modern bison under similar deep-snow conditions exhibit less enamel wear on identical grasses directly confirms the proposed causal mechanism.
Showing that the hypothesized cause produces the observed effect in an analogous modern setting provides strong supportive evidence.

Anahtar Kavram

Validating a causal mechanism by demonstrating that the cause produces the observed effect under analogous conditions
Tahmini Süre:1m 15s
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