Speciation

A species is a group of animals capable of interbreeding and producing fertile offspring. In speciation a group of organisms has changed so much that they are no longer able to mate with members of the population in which they were once a member. There are three main forms of speciation:

• Allopatric speciation occurs when a population is divided by a geographic barrier. With no interbreeding occurring between the members of the separated populations, the genetic makeup of the two groups gradually changes through successive generations so that if the barrier were to be removed they would no longer be able to reproduce together.
  
  
• Sympatric speciation occurs when a new species is formed without geographic isolation. Balanced polymorphism is an example of sympatric speciation that occurs when members of a population only interbreed with other members that share a certain allele (i.e. fur color). Eventually, the gene pool is altered to the point that a new species is formed. Polyploidy is the possession of more than two sets of chromosomes and is common in plants. Hybridization occurs when members of two different species have offspring that become different species.
  
  
• Adaptive radiation is the sudden evolution of many species from a single ancestor.