Well, it helps to know what the two terms are. Biotic potential is a population's ability to reproduce under optimum conditions, where there are no limitations, no restricting factors. And then, you guessed it, any factor that tends to restrict a population's ability to reproduce is termed an environmental factor. For example, there is a lake in a neighboring city that has experienced at least two fish-kills, where lots of fish show up at the surface of the lake dead. It was determined the oxygen levels in the lake had dipped past acceptable norms, so there wasn't enough oxygen for the fish to breathe, and they died. Another good example was a lab experiment that showed the exponential growth of a culture of bacteria in a petri dish measured against time. The population steadily climbed for seven hours, then ran out of agar, the medium bacteria feed on, whereupon the population numbers dwindled at an alarming rate. So a populations biotic potential may be limited by the interplay and influence of one or more environmental resistance factors.