Question

In cockroach, identify the incorrectly matched pair:

• A. Ommatidium -- chordotonal organ
• B. Rhabdome -- light sensitive structure
• C. Crystalline cone -- Transparent conical structure
• D. Cornea -- refractive region

Hint:

Remember that chordotonal organs are for hearing and vibration sensing, usually located in legs and antennae.
Always relate ommatidia to vision and compound eyes.

Answer 1

The Correct Option is A

Step 1: Recall what each structure in a cockroach eye or sensory system does.
The compound eye is built from thousands of ommatidia, each with a cornea, crystalline cone and light sensitive rhabdome, while chordotonal organs are a completely separate mechanoreceptor system for detecting vibration and stretch.
Step 2: Check the visual structure pairs.
Rhabdome as the light sensitive part, crystalline cone as the transparent conical lens like structure, and cornea as the refractive outer layer are all correctly described.
Step 3: Spot the mismatched pair.
Calling an ommatidium a chordotonal organ mixes up two unrelated systems, a visual receptor unit is being wrongly paired with a stretch and vibration sensing organ.
Final answer: Option 1, ommatidium, chordotonal organ.