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Name: Kim R.
Status: educator
Age: 40s
Location: N/A
Country: N/A
Date: Tuesday, May 07, 2002

I have been asked by a student, "How did the venomous snakes evolve? Why did some snakes become venomous and other not for instance, a garter snake and a rattler." I do know that some are constrictors and did not have the need for a toxic venom, but that does not account for the differences between vipers and a non-poisonous snake.

I hope you get a more specific reply from someone who knows more about snakes than I do, but my stock reply to questions of "why" things happen in nature is, "because it works." Evolution is a somewhat random process of mutation and adaptation, and if something happens that works it will then be selected for and enhanced. If a mutation improves survival chances then it will be selected for in future generations, if not, it will disappear.

J. Elliott

Venomous snakes are predators seeking fast moving prey, usually mammals. They have evolved because their niche includes chasing their food. Snakes can not move very fast so the ambush and strike will allow the snake to eventually catch up to the previously faster moving but now dead prey. These snakes use their tongues to sense the heat trail produced by the warm blooded mammal. Garter snakes and the like have it easier in that their prey are slow to move in the first place, such as insects, etc. It would be a waste to be posionous when you don't need it. Evolution has fine tuned all existing organisms, so snakes are the way they are because it works. Natural selection is a powerful force, but effective in developing the best species.

Steve Sample

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