Question

The lens of many vertebrate eyes is a crystallized form of a protein that also functions in digestion as a metabolic enzyme. This shows that
A. Vision and digestion co-evolved
B. Digestion necessarily evolved prior to vision since it is a more basic function
C. Evolution in opportunistic
D. Vision and digestion evolved around the same time

Answer 1

According to the options given in the question, it is possible that “Vision and digestion are co-evolved”.

This could be due to the evolutionary history of the protein. As per the evolution theory, it is possible for a lineage that is evolving to reuse an existing gene for another purpose.

This is what has probably happened here, where the protein is present in the lens and also aids in digestion.

Lens of many vertebrate eyes contains crystallin which is a water soluble structural protein which gives transparency to the lens and cornea. It increases the refractive index and does not obstruct light. It has been found that some crystallins are active enzymes and some which are inactive enzymatically show homology to some enzymes. It shows that evolution is opportunistic where one structure evolved for some use can be later evolved to perform any other function if any such opportunity arises. These evolutionary instances are called pre adaptations. A classic example of it is evolution of feathers in birds which appeared as thermoregulatory structures which later got evolved into flight organs.