Who was Ernst Mayr?

Biologist Ernst Mayr died last week at the age of 100. Mayr's work was key in developing the theory of evolution. He improved upon the theory of Evolution, placing a key piece in Darwin's evolution puzzle. Darwin's famous book "Origin of Species" did not include a clear definition of the term "species". Mayr clarified the definition, explaining that a species is a group of organisms, capable of breeding among themselves, but unable to breed with others. New species can develop when an existing species splits up into two groups, and the two groups get isolated from each other, usually by geography. In time, the members of the groups will physically change to the point where they are too different to breed with members of the other group. When this happens, the groups are considered two different species. This idea is now widely accepted, and is known to biologists as allopatric speciation. Mayr is also credited as being one of the key biologists who first established the relationship between evolution with genetics. Link.