Evolutionary biology is the subfield of biology that studies the evolutionary processes that produced the diversity of life on Earth, starting from a single origin of life. These processes include natural selection, common descent, and speciation.
The discipline emerged through what Julian Huxley called the modern evolutionary synthesis (of the 1930s) of understanding from several previously unrelated fields of biological research, including genetics, ecology, systematics and palaeontology.
Current research has widened to cover the genetic architecture of adaptation, molecular evolution, and the different forces that contribute to evolution including sexual selection, genetic drift and biogeography. The newer field of evolutionary developmental biology ("evo-devo") investigates how embryonic development is controlled, thus creating a wider synthesis that integrates developmental biology with the fields covered by the earlier evolutionary synthesis.
The study of evolution is the central unifying concept in biology. Biology can be divided in various ways. One way is by the level of biological organisation, from molecular to cell, organism to population. Another way is by taxonomic group, with fields such as zoology (all animals), ornithology (birds), and herpetology (reptiles and amphibians). A third way is by approach, such as field biology, theoretical biology, experimental evolution, and palaeontology. These alternative ways of dividing up the subject can be combined with evolutionary biology to create subfields like evolutionary ecology and evolutionary developmental biology.