5.5 Population Genetics- Isolation & Speciation

Speciation:

• Within a population of one species there are groups of interbreeding individuals.
• Within each populations there are breeding sub-units called demes.
• Individuals in a deme tend to breed with each other more often than they do with individuals of other demes. 
• New species arise when some barrier to reproduction occurs so that the gene pool is divided and the flow of genes between separate demes may cease.
• Such a barrier which effectively prevents gene exchange between demes is called an isolating mechanism.
• If the separation is long-term, eventally the two groups will be so different that two new species, incapable of interbreeding, are formed.
• The separate species will each have their own gene pool. This process is called speciation.

Isolation Leading to Speciation:

• For new species to develop from a population, some form of isolating mechanism is required.
• There are two main forms of isolating mechanisms.

Forms of Isolating Mechanism:

• Geographical isolation. This occurs when the population become physically split into separate demes. The physical barrier may be a mountain or a river or any feature which prevents the population of the…