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Evolutionary biology

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Evolutionary biology is a sub-field of biology concerned with the origin and descent of species, as well as their change, multiplication, and diversity over time. Biologically, evolution is the change in the inherited traits of a population from generation to generation. These traits are the expression of genes that are copied and passed on to offspring during reproduction. Mutations in these genes can produce new or altered traits, resulting in heritable differences (genetic variation) between organisms. New traits can also come from transfer of genes between populations, as in migration, or between species, in horizontal gene transfer. Evolution occurs when these heritable differences become more common or rare in a population, either non-randomly through natural selection or randomly through genetic drift.

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Darwins first tree
Evolutionary thought has roots in antiquity as philosophical ideas known to the Greeks, Romans, Indians, Chinese and Muslims. Until the 18th century, however, Western biological thought was dominated by essentialism, the idea that living forms are static and unchanging in time. During the Enlightenment, evolutionary cosmology and the mechanical philosophy spread from the physical sciences to natural history, and naturalists such as Maupertuis and Georges-Louis Leclerc, Comte de Buffon focused on the variability of species. The emergence of paleontology (and with it the notion of extinction), as well as the dramatic expansion of known species, helped undermine the traditional static view of nature. The first full theory of evolution was proposed by Jean-Baptiste Lamarck in the early 19th century; Lamarck's theory was based on the idea that species had an innate drive that pushed them up the great chain of being and that the mechanism of inheritance of acquired characteristics helped them adapt to local conditions. The evolutionary theory often referred to as Darwinism was first publicly put forth by Charles Darwin and Alfred Russel Wallace and discussed in detail in On the Origin of Species, published by Darwin in 1859. Darwinism, which unlike Lamarck's theory proposed common descent and a branching tree of life, was based on natural selection, and synthesized a wide range of evidence from animal husbandry, biogeography, geology, morphology, and embryology. The debate over Origin would play a key role in the displacement of natural theology by methodological naturalism in the life sciences, and raised profound questions about human nature and the place of humanity in the natural world.

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Credit: Matilda

The last known Thylacine photographed at Hobart (formerly Beaumaris) Zoo in 1933. A scrotal sac is not visible in this or any other of the photos or film taken, leading to the supposition that "Benjamin" was a female, but the existence of a scrotal pouch in the Thylacine makes it impossible to be certain


Did you know...

  • ...that adaptations enable living organisms to cope with environmental stresses and pressures?
  • ...that maintained gene flow between two populations can also lead to a combination of the two gene pools, reducing the genetic variation between the two groups?
  • ...that all forms of natural speciation have taken place over the course of evolution, though it still remains a subject of debate as to the relative importance of each mechanism in driving biodiversity?
  • ...that despite the relative rarity of suitable conditions for fossilization, approximately 250,000 fossil species are known?
  • ...that genetic sequence evidence thus allows inference and quantification of genetic relatedness between humans and other apes?

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