Biology Evolution KMU 2024
PMDC Verified Question 9 of 47
What best describes the hind leg bones seen in the whale?
A
Vestigial structures that had a function in an ancestor
B
Analogous to the fin of living fish
C
Fossil structure from an extinct ancestor
D
Homologous structure of the wings of a bat
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Vestigial structures that had a function in an ancestor
Concept:

Anatomical oddities inside modern organisms offer direct proof of their evolutionary lineage.

Solution:

  • Modern whales evolved from four-legged terrestrial mammals.
  • As they transitioned to a fully aquatic lifestyle, their hind limbs became a hindrance to streamlined swimming.
  • Through natural selection, the hind legs shrank over millions of years. The remaining tiny pelvic and leg bones buried deep inside a modern whale's blubber are classic vestigial structures that had a function in a terrestrial ancestor.


Why other options are incorrect:

  • Homologous to bat wings: A whale's front flipper is homologous to a bat wing, but the hind leg bones are remnants of legs, not forelimbs.
  • Fossil: They are living bones inside a modern animal, not fossilized rocks.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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