Mechanisms of Isolation
Speciation occurs when a group within a species separates from other members of its species and develops its own unique characteristics. For that to occur, the group needs to become isolated, and this can take place in different ways.
Geographic: Populations of a species are divided by a geographic barrier such as a river, canyon or mountain range. The syllabus also wants you to consider habitat fragmentation and environmental disasters here.
Spatial: Let’s be honest, this is the same as geographic, QCAA. Perhaps consider this on a larger scale: species are separated by vast distances…
These isolating mechanisms lead to allopatric speciation.
Pre-mating isolation can also lead to sympatric speciation if individuals are in the same area.
Reproductive isolating mechanisms include mechanical isolation where copulation is attempted, but transfer of sperm does not take place (perhaps due to genital incompatibility), or females not recognising a mating dance. Temporal isolation can also take place when individuals do not mate because they are active at different times of day or in different seasons. This may be found in parapatric speciation.