barrier leads to the development of mechanisms intrinsic to the populations themselves that prevent exchange of genetic materials. Mechanisms that prevent mating between members of the two populations include: 1) ecographic isolation, the state in which two populations have become so specialized for their own very different environmental conditions that they could never survive to mate if suddenly placed in one anothers' ranges; 2) habitat isolation, the state in which two populations have come to prefer different habitats within the same range so that it would be highly unlikely that members of the two populations would ever meet to mate; 3) seasonal isolation, the state in which two populations would be highly unlikely to mate, even if they were in the same range or same habitat, because they have evolved to have mating seasons at different times of the year; 4) behavioral isolation, the state in which two populations have evolved entirely different courting rituals so that the courtship display of the male of one species is unlikely to attract the female of the other species; 5) mechanical isolation, the state in which a structural difference, such as in the genitalia of the two populations, makes the physical act of mating between potential partners from the two different populations impossible.
Should mating between members of two different species actually occur, mechanisms that prevent the survival to birth of hybrids, individuals with parents from separate species, include: 1) gametic isolation, the state in which fertilization is prevented because of the inhospitable nature of one species' female
