|Question 8Verbal

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The blue shark and the striped marlin are ectothermic (cold-blooded) fish, whereas the salmon shark and the Pacific bluefin tuna are regional endotherms—they retain metabolic heat resulting in body temperatures above the ambient water temperature. Unlike those of ectotherms, regional endotherms' hearts have a relatively high proportion (greater than 30%) of compact myocardial tissue, which is needed to maintain these animals' blood pressure. In a 2023 study, Haley R. Dolton and colleagues found that basking sharks—planktivorous filter-feeders that were classified as full ectotherms at the time—have hearts consisting of 47% compact myocardial tissue, thereby undermining that classification.
According to the text, which choice most accurately describes the importance of the percentage of compact myocardial tissue in the basking shark's heart?
It is insufficient to establish that the basking shark should be categorized as Dolton and colleagues suggest.
A
It is higher than that of the salmon shark, a regional endotherm, despite the basking shark being a full ectotherm.
B
It is higher than that of the Pacific bluefin tuna, a regional endotherm, which calls into question the basking shark's status as a regional endotherm.
C
It is, by itself, sufficient to invalidate how the basking shark has been categorized in the past.
D