Some animals are toxic

Think of the molecular target of a neurotoxic alkaloid as a lock,and the alkaloid itself as the key.When the toxic key slides into the lock,it sets off a cascade of chemical and electrical signalsthat can cause paralysis,unconsciousness,and eventually death.But if you change the shape of the lock,the key can’t fit.For poison dart frogs and many other animals with neurotoxic defenses,a few genetic changes alter the structure of the alkaloid-binding site just enough to keep the neurotoxin from exerting its adverse effects.