Editing Theodosius Dobzhansky (section)

=== ''Genetics and the Origin of Species'' ===
Theodosius Dobzhansky published three editions of his book ''[[Genetics and the Origin of Species]]''. Although the book was meant for people with a background in biology, it was easily understood.<ref name=":3">{{Cite journal|last=Zirkle|first=Conway|date=1942|title=Review of Genetics and the Origin of Species|journal=Isis|volume=34|issue=2|pages=181|jstor=226232|doi=10.1086/347782}}</ref> In the fields of genetics and evolution, Dobzhansky's book is acknowledged as one of the most important books ever written. With each revision of ''Genetics and the Origin of Species'', Dobzhansky added new material on crucial, up to date topics, and removed material he deemed to be no longer crucial. His book sparked trends in genetic research and theory.<ref name=":4">{{Cite journal|last=Simpson|first=G. G.|date=1952|editor-last=Dobzhansky|editor-first=Theodosius|title=Evolutionary Genetics|journal=Evolution|volume=6|issue=2|pages=246–247|doi=10.2307/2405629|jstor=2405629}}</ref>

The first edition of ''Genetics and the Origin of Species'' (1937) highlighted the most recent discoveries in genetics and how they applied to the concept of evolution.<ref name=":3" /> The book starts by addressing the problem of evolution and how modern discoveries in genetics could help find a solution. The book covers the chromosomal basis of [[Mendelian inheritance|Mendelian Inheritance]], how the effects from changes in chromosomes greater than gene mutations are common and acceptable, and how mutations form racial and specific differences.<ref name=":5">{{Cite journal|last=Zirkle|first=Conway|date=1939|title=Review of Genetics and the Origin of Species|journal=Isis|volume=30|issue=1|pages=128–131|jstor=225596|doi=10.1086/347504}}</ref> Dobzhansky explained how three levels could describe the processes of evolutionary population genetics: (1) the origin of raw materials by mutations of genes and chromosomes, (2) the changes in populations by changes in frequencies and combinations of mutations, (3) the fixation of changes by reproductive isolation.<ref name=":4" /> To support his writing and research, the bibliography was twenty-eight pages long with around six hundred sources.<ref name=":5" />

In Dobzhansky's second edition of ''Genetics and the Origin of Species'' (1941), four years had gone by and he was able to add more research and advancements made in genetics. Around half of the new research he found was added to the last two chapters in his book: Patterns of Evolution, and Species as Natural Units. In the second to last chapter, Patterns of Evolution, Dobzhansky explained how on the path to a new adaptation, a method could be used to where a species could go through a less adaptive stage. The last chapter, Species as Natural Units, Dobzhansky explained some of the contributions made in genetics to what was called "the new systematics". Dobzhansky's second edition of the book also had twice as many sources in the bibliography than the first edition.<ref name=":3" />

In the third revision of ''Genetics and the Origin of Species'' (1951), Dobzhansky rewrote all ten chapters on: Isolating Mechanisms, Mutation in Populations, Organic Diversity, Heredity and Mutation, Race Formation, Selection, Adaptive Polymorphism, Hybrid Sterility, Species as Natural Units, and Patterns of Evolution. Dobzhansky decided to remove the chapter on Polyploidy in the third edition.<ref>{{Cite journal|last=Andrews|first=Ted F.|date=1952|title=Review of Genetics and the Origin of Species|journal=The American Biology Teacher|volume=14|issue=7|pages=196|doi=10.2307/4438411|jstor=4438411}}</ref> The new chapter on Adaptive Polymorphism highlighted Dobzhansky's research since the second edition. He included precise, quantitative evidence on effective [[natural selection]] in laboratory and free populations.<ref name=":4" />