2) Speciation

• The lowest level in Linnaeus's classification system is the 'species'.
• Members of a species are similar enough to be able to breed with each other and

  produce fertile offspring.
• Alfred Russel Wallace, who proposed a theory for evolution, also worked on a theory

  of speciation, i.e. how new species develop:

  1. Populations become physically isolated from each other, e.g. by a mountain range or ocean
  2. Gentic varation is present between the two populations
  3. Natural selection operates ddifferently in the two populations.
  4. The populations become so different that successful interbreeeding is no longer possible
•  Wallace's theory is supported by recent studies.