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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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Extinction is the termination of a species via the death of its last member. A taxon may become functionally extinct before the death of its last member if it loses the capacity to reproduce and recover. As a species‘ potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly “reappears” (typically in the fossil record) after a period of apparent absence.

Over five billion species are estimated to have died out. It is estimated that there are currently around 8.7 million species of eukaryotes globally, possibly many times more if prokaryotes are included. Notable extinct animal species include non-avian dinosaurs, saber-toothed cats, and mammoths. Through evolution, species arise through the process of speciation. Species become extinct when they are no longer able to survive in changing conditions or against superior competition. The relationship between animals and their ecological niches has been firmly established. A typical species becomes extinct within 10 million years of its first appearance, although some species, called living fossils, survive with little to no morphological change for hundreds of millions of years, though this claim has been disputed. (Full article…)

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

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

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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 evolution of sex is a major puzzle of evolutionary biology, due to the so-called two-fold cost of sex?
… that Perfect Imperfection, a 2004 science fiction novel by Polish writer Jacek Dukaj, raises the issues of technological singularity, transhumanism and the anthropic principle, and presents a unique model of human 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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