Portal:Evolutionary biology

The Evolutionary Biology Portal

Introduction

Evolutionary biology is a subfield of biology that analyzes the four mechanisms of evolution: natural selection, mutation, genetic drift, and gene flow. Natural selection was independently discovered as the engine of evolution by Charles Darwin and Alfred Russel Wallace, based on patterns in the geographic distribution of species. Gregor Mendel discovered the laws of heredity. R. A. Fisher unified Darwin and Mendel in the modern synthesis.

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. Evolution accounts for the unity and diversity of life on Earth; Theodosius Dobzhansky famously said that nothing in biology makes sense without it. (Full article...)

Selected article -

The rattlesnake *Crotalus oreganus* eating its prey, which it uses its venom to subdue

Venom in snakes and some lizards is a form of saliva that has been modified into venom over its evolutionary history. In snakes, venom has evolved to kill or subdue prey, as well as to perform other diet-related functions. While snakes occasionally use their venom in self defense, this is not believed to have had a strong effect on venom evolution. The evolution of venom is thought to be responsible for the enormous expansion of snakes across the globe.

The evolutionary history of snake venom is a matter of debate. Historically, snake venom was believed to have evolved once, at the base of the Caenophidia, or derived snakes. Molecular studies published beginning in 2006 suggested that venom originated just once among a putative clade of reptiles, called Toxicofera, approximately 170 million years ago. Under this hypothesis, the original toxicoferan venom was a very simple set of proteins that were assembled in a pair of glands. Subsequently, this set of proteins diversified in the various lineages of toxicoferans, including Serpentes, Anguimorpha, and Iguania: several snake lineages also lost the ability to produce venom. The Toxicoferan hypothesis was challenged by studies in the mid-2010s, including a 2015 study which found that venom proteins had homologs in many other tissues in the Burmese python. The study therefore suggested that venom had evolved independently in different reptile lineages, including once in the Caenophid snakes. Venom containing most extant toxin families is believed to have been present in the last common ancestor of the Caenophidia: these toxins subsequently underwent tremendous diversification, accompanied by changes in the morphology of venom glands and delivery systems. (Full article...)

List of selected articles

General images -

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

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

Selected picture -

Orange Band, the last Dusky Seaside Sparrow died in 1987 in a captive facility in the Walt Disney World Resort

Did you know... -

... that Variation and Evolution in Plants is one of the four canonical texts of the modern evolutionary synthesis and that all four texts were compiled following the authors' presentation of the Jesup Lectures at Columbia University?
... 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 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?

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