Portal:Evolutionary biology

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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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Punctuated equilibrium is a theory in evolutionary biology which proposes that most sexually reproducing species will experience little evolutionary change for most of their geological history (in an extended state called stasis). When evolution occurs, it is localized in rare, rapid events of branching speciation (called cladogenesis). Cladogenesis is simply the process by which species split into two distinct species, rather than one species gradually transforming into another. Punctuated equilibrium is commonly contrasted against the theory of phyletic gradualism, which states that evolution generally occurs uniformly and by the steady and gradual transformation of whole lineages (anagenesis); in this view, evolution is seen as generally smooth and continuous. In 1972 paleontologists Niles Eldredge and Stephen Jay Gould published a landmark paper developing this theory and called it punctuated equilibria, their paper was built upon Ernst Mayr's theory of geographic speciation, I. Michael Lerner's theories of developmental and genetic homeostasis, as well as their own empirical research. Eldredge and Gould proposed that the degree of gradualism commonly attributed to Charles Darwin was virtually nonexistent in the fossil record, and that stasis dominates the history of most fossil species.
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Gene-duplication
Credit: User:TimVickers

The image depicts the duplication of part of a chromosome.

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Did you know...

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  • ...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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