How did snakes develop venom as a way of killing when no other reptiles did (and so few animals have)? How did the variations in kinds of venoms come about? Did constricting snakes lose their venom?
In: Biology
Venom is an extremely advantageous trait. It takes a lot of muscular power and body adaptations to mechanically capture and subdue prey, which expends a lot of energy. So being able to do it chemically would allow an animal to kill prey with less risk to itself.
The prevailing theory is that venom first evolved in early reptiles as simple modified salivary glands that produced digestive proteins. Reptiles with this trait presumably fared better than those without, and continued to develop a fanged injection system and more powerful venom as time went on. Correspondingly, many more reptiles lost their venom or fangs, but still carry the genes in their DNA.
Variations in venom are often prompted by prey gradually evolving resistance to it, as some venom mechanisms can be defeated by biological adaptations.
There are a few types of venomous reptiles that are not snakes. Wiki includes: Gila monster and its kin the Mexican Bearded lizards and the Komodo Dragon and some of its kin. (They used to think that was all bacteria, but found that was incorrect.)
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