poison

Question
QUESTION: Where do reptiles like snakes, lizards, scorpion, etc. get their venom from?

ANSWER: They have glands which produce it. Much the same way mammals have glands which produce milk.

---------- FOLLOW-UP ----------

QUESTION: You said that poisonous animals get their venom through glands. But what is the origin of poison (in these glands)? Also how do they constantly increase the intensity of their venom?

Answer
We should say it is venom we are talking about not poison.  I believe venom is a protein conplex (a 3 dimensional bundle of amino acids assembled by cells), therefore the origin would be the food the snake eats.  I'm not sure I understand your second question, try that one again for me.