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The Evolutionary Biology Portal

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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...)

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In biology, phylogenetics (/ˌfaɪloʊdʒəˈnɛtɪks, -lə-/) is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data and observed heritable traits of DNA sequences, protein amino acid sequences, and morphology. The results are a phylogenetic tree—a diagram depicting the hypothetical relationships among the organisms, reflecting their inferred evolutionary history.

The tips of a phylogenetic tree represent the observed entities, which can be living taxa or fossils. A phylogenetic diagram can be rooted or unrooted. A rooted tree diagram indicates the hypothetical common ancestor of the taxa represented on the tree. An unrooted tree diagram (a network) makes no assumption about directionality of character state transformation, and does not show the origin or "root" of the taxa in question. (Full article...)

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

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

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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 the idea that molecular evolution is dominated by genetic drift originally took its name from the 1969 paper "Non-Darwinian 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?
... that botanist Edgar Anderson was a founding member of the Society for the Study of Evolution and an active member of the Religious Society of Friends?

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