- 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…