Question

Phytoecdysone is a defensive secondary chemical that __________.

• A. mimics a neurotransmitter and can cause paralysis or even death in caterpillars
• B. mimics insect hormones and interferes with insect metamorphosis
• C. belongs to a category of tannins and reduces the digestibility of plant tissues
• D. belongs to a category of lignins and deters herbivores

Hint:

Phytoecdysone is a plant steroid that closely resembles an insect's own molting hormone.

Answer 1

The Correct Option is B

Phytoecdysone is a chemical defense some plants use against insects. The question wants us to know exactly how it works, not just that it is "a defense chemical". Let's test each option against what phytoecdysone actually is.

1. Mimics a neurotransmitter, causes paralysis: That description fits neurotoxins like nicotine, which act on the nervous system. Phytoecdysone is not a nerve poison of this kind.
2. Mimics insect hormones, interferes with metamorphosis: Phytoecdysone is a plant-made steroid that closely resembles ecdysone, the hormone that times an insect's molts and its change into an adult. Eating it confuses this timing system and metamorphosis goes wrong. This matches.
3. A tannin that cuts digestibility: Tannins are a different chemical family; they bind to proteins in the gut and make plant matter harder to break down. Phytoecdysone is a steroid, not a tannin.
4. A lignin that deters herbivores: Lignins are structural, woody polymers that make plant tissue tough. Phytoecdysone has nothing to do with this structural role.

So phytoecdysone's defense strategy is chemical mimicry of a hormone, not a physical or nutritional barrier.

Let's summarize:

• Phytoecdysone copies the insect hormone ecdysone.
• This mimicry disturbs molting and metamorphosis in insects that eat the plant.

So the correct description is that phytoecdysone mimics insect hormones and interferes with insect metamorphosis.