Solution

Ommatidia are the visual units of the compound eyes of arthropods such as insects and crustaceans.
Each compound eye of a cockroach has about 2000 hexagonal ommatidia. Each ommatidium has its own lens (cornea), crystalline cone and photosensitive rhabdome, and forms a part of the image.
This produces mosaic vision, which is very sensitive to movement but less sharp.
Frogs and humans have camera-type eyes with a single lens and retina; the sunflower has no eyes.
So ommatidia serve the purpose of photoreception in the cockroach.

Concept Ommatidia of compound eye

Animal Kingdom in past papers

123 questions from this chapter have appeared across 27 exam years.