Compare rod and cone cells.

rods and cones are both light-sensitive cells;
rods are far more numerous than cones;
rods are distributed evenly throughout the retina while cones are particularly concentrated at and around the fovea;
rod cells are all the same/black and white vision but there are three types of cone cells (absorb red, blue and green colour)/colour vision;
rod cells absorb all the visible wavelengths but each type of cone cell absorbs a different range;
rods are longer and thinner, cones have cone shape;
rod cells are principally used for dim light and night vision while cone cells require bright light / rods give poor visual acuity while cones give good visual acuity;
the pigment in rod cells is rhodopsin while in cone cells is iodopsin;
each individual cone cell is fed to a single (bipolar) neuron, whereas many rod cells synapse with a single (bipolar) neuron;

There were some very good answers to this question, the majority did give comparative statements, and gained three marks. A few weaker candidates got the connections between the cells and the bipolar neurons the wrong way round.