3. Genetic diversity

• Genetic diversity is number of different alleles of genes in species or population. Large number of different alleles in population means large variety of different characteristics (e.g. blonde, brown, red or black hair) and high genetic diversity
• If population has low genetic diversity, might not be able to adapt to change in environment and whole population could be wiped out by single event (e.g. disease) Genetic diversity within population is increased by:

  • Mutations in DNA forming new alleles. Some of these can be advantageous, whilst others lead to problems
  • Different alleles being introduced into population when individuals from another population migrate into it and reproduce. Known as gene flow
• Genetic bottleneck is an event that causes big reduction in population, e.g. when large number of organisms within population die before reproducing. This reduces number of different alleles in gene pool and so reduces genetic diversity. Survivors reproduce and larger population is created from few individuals
• Founder effect describes what happens when just few organisms from a population start new colony and there are only small number of different alleles in initial gene pool. Frequency of each allele in new colony might be very different to frequency of those alleles in original population - e.g. Allele that was rare in original population might be more common in the new colony. Might lead to higher incidence of genetic disease.
• Founder effect can occur as result of migration to geographical separation or if new colony is separated from original population for another reason