mimics a neurotransmitter and can cause paralysis or even death in caterpillars
mimics insect hormones and interferes with insect metamorphosis
belongs to a category of tannins and reduces the digestibility of plant tissues
belongs to a category of lignins and deters herbivores
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The Correct Option isB
Solution and Explanation
Step 1: Know what phytoecdysones are.
Phytoecdysones (also called phytoecdysteroids) are steroid compounds made by certain plants, such as ferns and spinach, that are structurally very close to ecdysone, the hormone insects use to control molting and metamorphosis.
Step 2: Work out how they act as a defense.
When an insect eats plant tissue containing phytoecdysones, the compound mimics the insect's own molting hormone inside its body. This throws off the careful hormonal timing that controls larval molts and the change into a pupa or adult, so the insect's metamorphosis is disrupted, often to the point of death or failure to reproduce.
Step 3: Rule out the other options.
Option (A) describes a neurotoxin that mimics a neurotransmitter, which is how compounds such as nicotine or certain alkaloids act, not phytoecdysones.
Option (C) describes tannins, a separate class of plant polyphenols that bind proteins and make plant tissue harder to digest; phytoecdysones are steroids, not tannins.
Option (D) describes lignins, structural polymers that make plant cell walls tough and hard to chew; phytoecdysones are not lignins and do not work by physically deterring feeding.
Final Answer:
Phytoecdysone works by copying an insect's own hormone and derailing its metamorphosis.
\[ \boxed{\text{Mimics insect hormones and interferes with insect metamorphosis}} \]
