speciation

• speciation= formation of new species through the process of evolution.

  organisms of new species can no longer interbreed to produce fertile offspring.
• events leading to speciation

  • members of a population become isolated and no longer interbreed resulting in no gene flow between the two groups.
  • alleles within the groups continue to undergo random mutations. The environment of each group may be different or change, so different characteristics will be selected for and against.
  • accumulation of mutations and changes in allele frequencies eventually lead to large changes phenotype. Members become so different they can not interbreed. They are now reproductively isolated and are different species.
• allopatric speciation

  = isolation due to a physical barrier.

  • geographically isolated.
  • different selection pressures.
  • isolated group leads to founder effect which leads to genetic drift so there are more differences in the population so there is a change in allele frequencies.
• sympatric isolation

  = occurs in populations that share the same habitat.

  • two different species interbreed to produce fertile offspring.
  • offspring have different number of chromosomes to either parent and cant breed with them.
  • hybrid offspring are reproductively isolated.