AIIMS 2019 Biology Pisces MCQ Question

Option C highlights a significant anatomical difference between fish species: a ventral mouth is located on the underside of the head, typical of many bottom-dwelling species, while a terminal mouth is positioned at the front, common in more active swimmers. This distinction affects feeding strategies and ecological niches.

In contrast, option A compares the heart structures of different vertebrates; both 2-chambered and 3-chambered hearts serve specific functions in their respective organisms, making this option less relevant. Option B discusses scale size, which does not inherently indicate a functional difference, and option D refers to the presence or absence of swim bladders, which is a characteristic of certain fish but not a direct anatomical comparison like that in option C.