What are different isolating mechanisms? Discuss their role in speciation. (UPSC 2017, 20 Marks, )

विभिन्न पृथक्करण तंत्र क्या हैं? प्रजाति निर्माण में उनकी भूमिका पर चर्चा करें। (What are different isolating mechanisms? Discuss their role in speciation.)