volution

volution
Natural selection of a population for dark coloration.
A central organizing concept in biology is that life changes and develops throughevolution, and that all life-forms known have a common origin. Introduced into the scientific lexicon by Jean-Baptiste de Lamarck in 1809,[19] Charles Darwin established evolution fifty years later as a viable theory by articulating its driving force: natural selection.[20][21] (Alfred Russel Wallace is recognized as the co-discoverer of this concept as he helped research and experiment with the concept of evolution).[22]Evolution is now used to explain the great variations of life found on Earth.
Darwin theorized that species and breeds developed through the processes of natural selection and artificial selection or selective breeding.[23] Genetic drift was embraced as an additional mechanism of evolutionary development in the modern synthesis of the theory.[24]
The evolutionary history of the species— which describes the characteristics of the various species from which it descended— together with its genealogical relationship to every other species is known as its phylogeny. Widely varied approaches to biology generate information about phylogeny. These include the comparisons of DNA sequences conducted within molecular biology or genomics, and comparisons of fossils or other records of ancient organisms inpaleontology.[25]
Biologists organize and analyze evolutionary relationships through various methods, including phylogenetics, phenetics, and cladistics. For a summary of major events in the evolution of life as currently understood by biologists, see evolutionary timeline.
Historically, it wasn't evolution that was theorized to be the reason for biological speciation. Up into the 19th century, spontaneous generation, the belief that life forms could appear spontaneously under certain conditions, was widely accepted.[26] This misconception was challenged byWilliam Harvey, who even before the invention of the microscope was led by his studies to suggest that life came from invisible 'eggs.' In the frontispiece of his book Exercitationes de Generatione Animalium (Essays on the Generation of Animals), he expressed the basic principle ofbiogenesis: "Omnia ex ovo" (everything from eggs).[27]
A group of organisms have a common descent if they share a common ancestor. All organisms on the Earth, both living and extinct, have been or are descended from a common ancestor or an ancestral gene pool. This last universal common ancestor of all organisms is believed to have appeared about 3.5 billion years ago.[28] Biologists generally regard the collective universality of the genetic code as definitive evidence in favor of the theory of universal common descent for all bacteria, archaea, and eukaryotes