Portal:Evolutionary biology

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Introduction

Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life forms on Earth. Evolution holds that all species are related and gradually change over generations. In a population, the genetic variations affect the phenotypes (physical characteristics) of an organism. These changes in the phenotypes will be an advantage to some organisms, which will then be passed on to their offspring. Some examples of evolution in species over many generations are the peppered moth and flightless birds. In the 1930s, the discipline of evolutionary biology emerged through what Julian Huxley called the modern synthesis of understanding, from previously unrelated fields of biological research, such as genetics and ecology, systematics, and paleontology.

The investigational range of current research has widened to encompass the genetic architecture of adaptation, molecular evolution, and the different forces that contribute to evolution, such as sexual selection, genetic drift, and biogeography. Moreover, the newer field of evolutionary developmental biology ("evo-devo") investigates how embryogenesis is controlled, thus yielding a wider synthesis that integrates developmental biology with the fields of study covered by the earlier evolutionary synthesis. (Full article...)

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Mutationism is one of several alternatives to evolution by natural selection that have existed both before and after the publication of Charles Darwin's 1859 book On the Origin of Species. In the theory, mutation was the source of novelty, creating new forms and new species, potentially instantaneously, in sudden jumps. This was envisaged as driving evolution, which was thought to be limited by the supply of mutations.

Before Darwin, biologists commonly believed in saltationism, the possibility of large evolutionary jumps, including immediate speciation. For example, in 1822 Étienne Geoffroy Saint-Hilaire argued that species could be formed by sudden transformations, or what would later be called macromutation. Darwin opposed saltation, insisting on gradualism in evolution as geology's uniformitarianism. In 1864, Albert von Kölliker revived Geoffroy's theory. In 1901 the geneticist Hugo de Vries gave the name "mutation" to seemingly new forms that suddenly arose in his experiments on the evening primrose Oenothera lamarckiana. In the first decade of the 20th century, mutationism, or as de Vries named it mutationstheorie, became a rival to Darwinism supported for a while by geneticists including William Bateson, Thomas Hunt Morgan, and Reginald Punnett. (Full article...)

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The following are images from various evolutionary biology-related articles on Wikipedia.

Image 1Five types of chromosomal mutations (from Mutation)
Image 2Expression of homeobox (Hox) genes in the fruit fly (from Evolutionary developmental biology)
Image 3Embryology theories of Ernst Haeckel, who argued for recapitulation of evolutionary development in the embryo, and Karl Ernst von Baer's epigenesis (from Evolutionary developmental biology)
Image 4African pygmy kingfisher, showing coloration shared by all adults of that species to a high degree of fidelity. (from Speciation)
Image 5Homologous hox genes in such different animals as insects and vertebrates control embryonic development and hence the form of adult bodies. These genes have been highly conserved through hundreds of millions of years of evolution. (from Evolutionary developmental biology)
Image 6Male Drosophila pseudoobscura (from Speciation)
Image 7The structure of a eukaryotic protein-coding gene. A mutation in the protein coding region (red) can result in a change in the amino acid sequence. Mutations in other areas of the gene can have diverse effects. Changes within regulatory sequences (yellow and blue) can effect transcriptional and translational regulation of gene expression. (from Mutation)
Image 8Types of small-scale mutations (from Mutation)
Image 9The pax-6 gene controls development of eyes of different types across the animal kingdom. (from Evolutionary developmental biology)
Image 10A. Lancelet (a chordate), B. Larval tunicate, C. Adult tunicate. Kowalevsky saw that the notochord (1) and gill slit (5) are shared by tunicates and vertebrates. (from Evolutionary developmental biology)
Image 11Comparison of allopatric, peripatric, parapatric and sympatric speciation (from Speciation)
Image 12Mutation with double bloom in the Langheck Nature Reserve near Nittel, Germany (from Mutation)
Image 13A gene regulatory network (from Evolutionary developmental biology)
Image 14Reinforcement assists speciation by selecting against hybrids. (from Speciation)
Image 15Gene product distributions along the long axis of the early embryo of a fruit fly (from Evolutionary developmental biology)
Image 16This figure shows a simplified version of loss-of-function, switch-of-function, gain-of-function, and conservation-of-function mutations. (from Mutation)
Image 17Point mutations classified by impact on protein (from Mutation)
Image 18Among the centipedes, all members of the Geophilomorpha are constrained by a developmental bias to have an odd number of segments, whether as few as 27 or as many as 191. (from Evolutionary developmental biology)
Image 19A mutation has caused this moss rose plant to produce flowers of different colors. This is a somatic mutation that may also be passed on in the germline. (from Mutation)
Image 20Cichlids such as Haplochromis nyererei diversified by sympatric speciation in the Rift Valley lakes. (from Speciation)
Image 21Phyletic gradualism, above, consists of relatively slow change over geological time. Punctuated equilibrium, bottom, consists of morphological stability and rare, relatively rapid bursts of evolutionary change. (from Speciation)
Image 22Rhagoletis pomonella, the hawthorn fly, appears to be in the process of sympatric speciation. (from Speciation)
Image 23Prodryas persephone, a Late Eocene butterfly (from Mutation)
Image 24The distribution of fitness effects (DFE) of mutations in vesicular stomatitis virus. In this experiment, random mutations were introduced into the virus by site-directed mutagenesis, and the fitness of each mutant was compared with the ancestral type. A fitness of zero, less than one, one, more than one, respectively, indicates that mutations are lethal, deleterious, neutral, and advantageous. (from Mutation)
Image 25The lac operon. Top: repressed. Bottom: active.
1: RNA Polymerase, 2: Repressor, 3: Promoter, 4: Operator, 5: Lactose, 6–8: protein-encoding genes, controlled by the switch, that cause lactose to be digested (from Evolutionary developmental biology)
Image 26Turing's 1952 paper explained mathematically how patterns such as stripes and spots, as in the giant pufferfish, may arise, without molecular evidence. (from Evolutionary developmental biology)
Image 27A red tulip exhibiting a partially yellow petal due to a mutation in its genes (from Mutation)
Image 28Gap genes in the fruit fly are switched on by genes such as bicoid, setting up stripes across the embryo which start to pattern the body's segments. (from Evolutionary developmental biology)
Image 29A covalent adduct between the metabolite of benzo[a]pyrene, the major mutagen in tobacco smoke, and DNA (from Mutation)
Image 30Selection of disease-causing mutations, in a standard table of the genetic code of amino acids (from Mutation)
Image 31Speciation via polyploidy: A diploid cell undergoes failed meiosis, producing diploid gametes, which self-fertilize to produce a tetraploid zygote. In plants, this can effectively be a new species, reproductively isolated from its parents, and able to reproduce. (from Speciation)
Image 32Gaur (Indian bison) can interbreed with domestic cattle. (from Speciation)

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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

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Did you know... - show different entries

... that Herbert Spencer, secretary of the Derby Philosophical Society, first suggested the term "survival of the fittest" after reading Charles Darwin's idea of evolution?
... that despite the relative rarity of suitable conditions for fossilization, approximately 250,000 fossil species are known?
... that the evolution of sex is a major puzzle of evolutionary biology, due to the so-called two-fold cost of sex?

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