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Question

Difficulty: HardCommand of Evidence: Textual

According to Foster's rule, large mammal species isolated on islands often undergo dwarfism, evolving much smaller body sizes than their mainland counterparts. While researchers traditionally attribute this change to restricted resource availability on islands, evolutionary biologist Dr. Marcus Vance hypothesized that the primary driver of island dwarfism in large herbivores is actually the absence of large terrestrial predators, which relaxes the evolutionary pressure to maintain a large body size for defense.

Which finding, if true, would most directly support Vance's hypothesis?

  1. Island populations of a deer species coexisting with large predators showed no reduction in body size, whereas populations of the same species on islands with similar food resources but no predators grew significantly smaller over generations.Answer
  2. B
    Fossil evidence indicates that mainland populations of large herbivores experienced rapid declines in overall abundance when new carnivorous predators entered their habitats.
  3. C
    Small rodent species on predator-free islands evolved to be significantly larger than their mainland ancestors to better defend themselves against avian predators.
  4. D
    Large herbivore species residing on islands with abundant foliage and vegetation consistently maintained larger population sizes than those on resource-poor islands.

Answer

The finding that island populations of a deer species coexisting with large predators showed no reduction in body size, whereas populations of the same species on islands with similar food resources but no predators grew significantly smaller over generations.
The hypothesis suggests that the lack of predators, not food scarcity, is the main driver of island dwarfism in large herbivores. The finding comparing deer populations on islands with similar food resources demonstrates that dwarfism only occurs when predators are absent, which directly isolates predator presence as the key variable.

Step-by-Step Solution

1
Identify the main hypothesis or claim to be supported.
Vance's hypothesis states that the primary driver of island dwarfism in large herbivores is the absence of large terrestrial predators (which relaxes defense pressures), rather than limited food resources.
To support this claim, the correct finding must show that body size dwarfism is linked to predator presence/absence rather than resource availability.
2
Evaluate how each option addresses the variables of predator presence and resource availability.
The option comparing deer on islands with similar food resources but differing predator presence directly tests this relationship. It shows that dwarfism occurs only when predators are absent, holding food resources constant.
Isolating the hypothesized cause (absence of predators) while controlling for the alternative cause (food resources) provides the strongest logical support.

Key Concept

Textual evidence evaluation and hypothesis testing
Estimated Time:2m 0s
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Topics

Command of Evidence: Textual

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