speciation and artificial selection

• Speciation = the formation of new species through the process of evolution
• Allopatric speciation = the more common form of speciation and happens when some members of a population are separated from the rest of the group by a physical barrier
• Sympatric speciation = occurs within populations that share the same habitat
• Reproductive barriers:

  • prezygotic reproductive barriers
  • post zygotic reproductive barriers
• Prezygotic reproductive barriers = prevent fertilisation and the formation of a zygote
• Postzygotic reproductive barriers = reduce the viability or reproductive potential of offspring
• Artificial selection = fundamentally the same as natural selection except for the nature of the selection pressure applied. Instead of changes in the environment leading to survival of the fittest, it is the selection for breeding of plants or animals with desirable characteristics by farmers or breeders.
• Problems caused by inbreeding:

  Many genetic disorders are caused by recessive alleles. Organisms that are closely related are genetically similar and are likely to have the same recessive alleles. The breeding of closely related organisms therefore results in offspring which have a greater chance of being homozygous for these recessive traits.