Differentiate between the following pairs on the basis of what is mentioned within brackets:
Rod cells and Cone cells (pigment)
Topic: Rod cells and cone cells
Answer
ROD CELLS contain the pigment RHODOPSIN (visual purple).
CONE CELLS contain the pigment IODOPSIN (visual violet).
The brackets ask only for the PIGMENT, so name both — but the pairing is what matters, since papers offer all four combinations to catch a mismatch.
HOW TO KEEP THEM PAIRED: Rods with Rhodopsin, both beginning with R; Cones for Colour, both with C. That alone answers most questions on this topic.
RODS — rhodopsin — DIM light — black-and-white vision (which is why a nocturnal owl has a retina packed with rods) CONES — iodopsin — BRIGHT light — COLOUR vision (which is why we cannot distinguish colours in dim light)
RHODOPSIN is made from VITAMIN A, which is why a deficiency causes NIGHT BLINDNESS — the rods can no longer make enough pigment.
| Point of difference | Rod cells | Cone cells |
|---|---|---|
| Pigment | Rhodopsin (visual purple) | Iodopsin (visual violet) |
| Sensitive to | Dim light | Bright light |
| Vision given | Black and white | Colour |