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The Evolutionary Biology Portal

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Introduction

Evolutionary biology is the subfield of biology that studies the evolutionary processes such as natural selection, common descent, and speciation that produced the diversity of life on Earth. 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. 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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The Ediacaran (/ˌiːdiˈækərən/; formerly Vendian) biota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (c. 635–538.8 Mya). These were enigmatic tubular and frond-shaped, mostly sessile, organisms. Trace fossils of these organisms have been found worldwide, and represent the earliest known complex multicellular organisms. The term "Ediacara biota" has received criticism from some scientists due to its alleged inconsistency, arbitrary exclusion of certain fossils, and inability to be precisely defined.

The Ediacaran biota may have undergone evolutionary radiation in a proposed event called the Avalon explosion, 575 million years ago. This was after the Earth had thawed from the Cryogenian period's extensive glaciation. This biota largely disappeared with the rapid increase in biodiversity known as the Cambrian explosion. Most of the currently existing body plans of animals first appeared in the fossil record of the Cambrian rather than the Ediacaran. For macroorganisms, the Cambrian biota appears to have almost completely replaced the organisms that dominated the Ediacaran fossil record, although relationships are still a matter of debate. (Full article...)

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

Image 1Gaur (Indian bison) can interbreed with domestic cattle. (from Speciation)
Image 2A red tulip exhibiting a partially yellow petal due to a somatic mutation in a cell that formed that petal (from Mutation)
Image 3A. Lancelet (a chordate), B. Larval tunicate, C. Adult tunicate. Kowalevsky saw that the notochord (1) and gill slits (5) are shared by tunicates and vertebrates. (from Evolutionary developmental biology)
Image 4Male Drosophila pseudoobscura (from Speciation)
Image 5Three major single-chromosome mutations: deletion (1), duplication (2) and inversion (3). (from Mutation)
Image 6Comparison of allopatric, peripatric, parapatric and sympatric speciation (from Speciation)
Image 7The pax-6 gene controls development of eyes of different types across the animal kingdom. (from Evolutionary developmental biology)
Image 8African pygmy kingfisher, showing coloration shared by all adults of that species to a high degree of fidelity. (from Speciation)
Image 9A mutation has caused this moss rose plant to produce flowers of different colours. This is a somatic mutation that may also be passed on in the germline. (from Mutation)
Image 10Phyletic 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 11Gap 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 12Gene product distributions along the long axis of the early embryo of a fruit fly (from Evolutionary developmental biology)
Image 13The 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 14Point mutations classified by impact on protein (from Mutation)
Image 15Rhagoletis pomonella, the hawthorn fly, appears to be in the process of sympatric speciation. (from Speciation)
Image 16Among 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 17Turing'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 18A covalent adduct between the metabolite of benzo[a]pyrene, the major mutagen in tobacco smoke, and DNA (from Mutation)
Image 19This figure shows a simplified version of loss-of-function, switch-of-function, gain-of-function, and conservation-of-function mutations. (from Mutation)
Image 20Reinforcement assists speciation by selecting against hybrids. (from Speciation)
Image 21Homologous 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 22Prodryas persephone, a Late Eocene butterfly (from Mutation)
Image 23Types of small-scale mutations (from Mutation)
Image 24Speciation 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 25Selection of disease-causing mutations, in a standard table of the genetic code of amino acids (from Mutation)
Image 26Cichlids such as Haplochromis nyererei diversified by sympatric speciation in the Rift Valley lakes. (from Speciation)
Image 27Expression of homeobox (Hox) genes in the fruit fly (from Evolutionary developmental biology)
Image 28The 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 29Five types of chromosomal mutations (from Mutation)
Image 30Embryology 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 31The 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 32A gene regulatory network (from Evolutionary developmental biology)

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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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... that genetic sequence evidence thus allows inference and quantification of genetic relatedness between humans and other apes?
... that the idea that molecular evolution is dominated by genetic drift originally took its name from the 1969 paper "Non-Darwinian Evolution"?
... that despite the relative rarity of suitable conditions for fossilization, approximately 250,000 fossil species are known?

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