All of the following are homologous structures EXCEPT: (a) a bat wing (b) a bird wing (c) a butterfly wing (d) a penguin flipper
The correct answer and explanation is:
Correct Answer: (c) a butterfly wing
Homologous structures are anatomical features that are similar in form or structure but may differ in function. These structures arise from a common evolutionary ancestor and typically have similar underlying anatomy. For example, the forelimbs of mammals, birds, and reptiles show similar bone arrangements even though they may serve different purposes like flying, swimming, or grasping.
In this question, the bat wing, bird wing, and penguin flipper all contain the same basic set of bones — such as the humerus, radius, and ulna — indicating that they are derived from a common vertebrate ancestor. Despite their different uses (bats and birds for flying, penguins for swimming), the internal structure of these limbs is fundamentally the same, making them homologous.
In contrast, a butterfly wing is not homologous to the wings or limbs of birds, bats, or penguins. Butterfly wings are made of a thin membrane supported by a network of veins and lack bones entirely. They evolved independently in insects and do not share a common structural origin with the wings or limbs of vertebrates. Therefore, while butterfly wings perform the same function as bat or bird wings — flight — they do not share the same evolutionary origin or anatomical structure. This makes butterfly wings an example of analogous structures, not homologous ones.
Analogous structures arise when different organisms independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. In this case, the need for flight led to the evolution of wings in both insects and birds, but these wings evolved separately and from different ancestral origins.
Thus, the butterfly wing is not homologous and is the correct answer to the question.