What two things can alter the shape and function of an enzyme

Temperature can cause an enzymes shape and function to alter due to the fact that once an enzyme reaches its optimum level, if it goes over it begins to denature. If the temperature is below optimum, then an enzyme will work at a slower rate.  Also, the pH can affect an enzyme.  

as resources become scarce because of population growth, the growth decreases after few years due to lack of resources and food.