<u>Answer</u>: 
1. Type of medium - the nutrient availability is one of the vital factors for the growth of a bacterial colony. Thus, the used growth medium will fulfill this requirement. 
2. Incubation temperature - all bacteria have an optimal temperature range in which maximum growth is achieved. Any variations from this will result in negative effects on the amount of bacteria that are produced. 
3. Moisture - bacteria thrive in moist or wet environments. Thus, the availability of moisture is another vital factor for the growth of the colony.
 
        
             
        
        
        
He wanted to see how different traits passed through the pea plants he grew. To do this, he needed to cross polliante so that their were multiple parents affecting the genes of the new pea plant. If he self pollinated, all the new baby pea plants would Look the same as their parents and we wouldn't know as much as we do about genetics now