Portal:Evolutionary biology

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...)

Selected article -

Endless Forms Most Beautiful: The New Science of Evo Devo and the Making of the Animal Kingdom is a 2005 book by the molecular biologist Sean B. Carroll. It presents a summary of the emerging field of evolutionary developmental biology and the role of toolkit genes. It has won numerous awards for science communication.

The book's somewhat controversial argument is that evolution in animals (though no doubt similar processes occur in other organisms) proceeds mostly by modifying the way that regulatory genes, which do not code for structural proteins (such as enzymes), control embryonic development. In turn, these regulatory genes turn out to be based on a very old set of highly conserved genes which Carroll nicknames the toolkit. Almost identical sequences can be found across the animal kingdom, meaning that toolkit genes such as Hox must have evolved before the Cambrian radiation which created most of the animal body plans that exist today. These genes are used and reused, occasionally by duplication but far more often by being applied unchanged to new functions. Thus the same signal may be given at a different time in development, in a different part of the embryo, creating a different effect on the adult body. In Carroll's view, this explains how so many body forms are created with so few structural genes. (Full article...)

List of selected articles

General images -

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

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

Selected picture -

The passenger pigeon, one of several species of extinct birds, was hunted to extinction over the course of a few decades.

Did you know... -

... that William King Gregory, a leading authority on vertebrate evolution and the preeminent expert on human dentition, was initially taken in by the Piltdown Man, a hoax which was purported to be an early human?
... that maintained gene flow between two populations can also lead to a combination of the two gene pools, reducing the genetic variation between the two groups?
... that despite the relative rarity of suitable conditions for fossilization, approximately 250,000 fossil species are known?

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