Portal:Evolutionary biology

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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...)

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Evolution of sexual reproduction describes how sexually reproducing animals, plants, fungi and protists could have evolved from a common ancestor that was a single-celled eukaryotic species. Sexual reproduction is widespread in eukaryotes, though a few eukaryotic species have secondarily lost the ability to reproduce sexually, such as Bdelloidea, and some plants and animals routinely reproduce asexually (by apomixis and parthenogenesis) without entirely having lost sex. The evolution of sexual reproduction contains two related yet distinct themes: its origin and its maintenance. Bacteria and Archaea (prokaryotes) have processes that can transfer DNA from one cell to another (conjugation, transformation, and transduction), but it is unclear if these processes are evolutionarily related to sexual reproduction in Eukaryotes. In eukaryotes, true sexual reproduction by meiosis and cell fusion is thought to have arisen in the last eukaryotic common ancestor, possibly via several processes of varying success, and then to have persisted.

Since hypotheses for the origin of sex are difficult to verify experimentally (outside of evolutionary computation), most current work has focused on the persistence of sexual reproduction over evolutionary time. The maintenance of sexual reproduction (specifically, of its dioecious form) by natural selection in a highly competitive world has long been one of the major mysteries of biology, since both other known mechanisms of reproduction – asexual reproduction and hermaphroditism – possess apparent advantages over it. Asexual reproduction can proceed by budding, fission, or spore formation and does not involve the union of gametes, which accordingly results in a much faster rate of reproduction compared to sexual reproduction, where 50% of offspring are males and unable to produce offspring themselves. In hermaphroditic reproduction, each of the two parent organisms required for the formation of a zygote can provide either the male or the female gamete, which leads to advantages in both size and genetic variance of a population. (Full article...)

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

Image 1Gap 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 2The 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 3This figure shows a simplified version of loss-of-function, switch-of-function, gain-of-function, and conservation-of-function mutations. (from Mutation)
Image 4A. 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 5Gene product distributions along the long axis of the early embryo of a fruit fly (from Evolutionary developmental biology)
Image 6Mutation with double bloom in the Langheck Nature Reserve near Nittel, Germany (from Mutation)
Image 7Five types of chromosomal mutations (from Mutation)
Image 8Prodryas persephone, a Late Eocene butterfly (from Mutation)
Image 9Reinforcement assists speciation by selecting against hybrids. (from Speciation)
Image 10Embryology 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 11A covalent adduct between the metabolite of benzo[a]pyrene, the major mutagen in tobacco smoke, and DNA (from Mutation)
Image 12Selection of disease-causing mutations, in a standard table of the genetic code of amino acids (from Mutation)
Image 13Types of small-scale mutations (from Mutation)
Image 14Rhagoletis pomonella, the hawthorn fly, appears to be in the process of sympatric speciation. (from Speciation)
Image 15A gene regulatory network (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 pax-6 gene controls development of eyes of different types across the animal kingdom. (from Evolutionary developmental biology)
Image 18Homologous 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 19Expression of homeobox (Hox) genes in the fruit fly (from Evolutionary developmental biology)
Image 20Speciation 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 21The 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 22African pygmy kingfisher, showing coloration shared by all adults of that species to a high degree of fidelity. (from Speciation)
Image 23Gaur (Indian bison) can interbreed with domestic cattle. (from Speciation)
Image 24Point mutations classified by impact on protein (from Mutation)
Image 25Turing'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 26Cichlids such as Haplochromis nyererei diversified by sympatric speciation in the Rift Valley lakes. (from Speciation)
Image 27Comparison of allopatric, peripatric, parapatric and sympatric speciation (from Speciation)
Image 28Male Drosophila pseudoobscura (from Speciation)
Image 29A red tulip exhibiting a partially yellow petal due to a mutation in its genes (from Mutation)
Image 30The 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 31A 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 32Among 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)

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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 the idea that molecular evolution is dominated by genetic drift originally took its name from the 1969 paper "Non-Darwinian Evolution"?
... that genetic sequence evidence thus allows inference and quantification of genetic relatedness between humans and other apes?

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