In "Life of Pi" how does Pi combine and use religion and science to survive on the lifeboat?
Science, especially in the form of zoology, helped Pi quite a bit in his survival on the lifeboat. Pi was able to use his knowledge of animals, especially in regards to the concept of "alpha males" and territorialism. As soon as Pi realized that he was alone on a life raft with a starving tiger, he knew that he had to establish himself as the alpha male, with very clear-cut boundaries, so that Richard Parker would not harm him. He very cleverly enlists the use of the whistle and intimidation tactics to establish boundaries, and the fact that he is the sole provider of food and nourishment for the both of them.
Pi also uses his knowledge of science in gathering water for drinking, in providing food for himself and Richard Parker, and in many other ways as he struggles to survive. Religion comes into play also; he still prays every day that he can on the lifeboat, and his faith keeps him from total and complete despair. Studies have shown that in survival situations, faith in God is one of the most important factors in determining whether or not someone survives. Pi, coming into the situation with faith in many different religions, had more resources than others in his attempts to survive.
Both science and religion were crucial factors in Pi's survival; Martel spent the entire first third of the book discussing both of those issues at length, because they did play such an important role. I hope that those thoughts helped; good luck!