system
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human
Evolution of defensive poisons

How can a defensive poison (such as that of a poisonous frog)  evolve if the selective pressure depends on its predator knowing it's poisonous? That is there no advantage to the individual to being poisonous if you die anyway.

 Is that why poisonous animals are colourful,  because only the distinctive ones are remembered by the poisoned predator as being poisonous? (that is only animals that evolve a poison and a distinctive colour simultaneously can pass on a benefit to their kin?
gpt
The selective pressure doesn't depend on the predator knowing it's poisonous.  The poison kills the predator, regardless of whether it knows what it ate was good for it or bad for it - however, those predators that don't eat the poisonous prey will live, while those that don't will die.  Eventually, you select for the predators that avoid the poisonous animal - if it happens to have a distinct colouring, that's ok.

The distinctive colouring would, by expectation, be secondary, as the predators have stopped eating the animal that isn't camouflaged so well any more.  Otherwise, if the fancy colour evolved before the toxin, the brightly coloured prey would be easier to see, and thus would have been depleted faster, favouring those that are better camoflaged.