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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Teleology in biology is the use of the language of goal-directedness in accounts of evolutionary adaptation, which some biologists and philosophers of science find problematic. The term teleonomy has also been proposed. Before Darwin, organisms were seen as existing because God had designed and created them; their features such as eyes were taken by natural theology to have been made to enable them to carry out their functions, such as seeing. Evolutionary biologists often use similar teleological formulations that invoke purpose, but these imply natural selection rather than actual goals, whether conscious or not. Some biologists and religious thinkers held that evolution itself was somehow goal-directed (orthogenesis), and in vitalist versions, driven by a purposeful life force. With evolution working by natural selection acting on inherited variation, the use of teleology in biology has attracted criticism, and attempts have been made to teach students to avoid teleological language.

Nevertheless, biologists still often write about evolution as if organisms had goals, and some philosophers of biology such as Francisco Ayala and biologists such as J. B. S. Haldane consider that teleological language is unavoidable in evolutionary biology. (Full article...)

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

Image 1Phyletic 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 2A. 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 3The 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 4A covalent adduct between the metabolite of benzo[a]pyrene, the major mutagen in tobacco smoke, and DNA (from Mutation)
Image 5This figure shows a simplified version of loss-of-function, switch-of-function, gain-of-function, and conservation-of-function mutations. (from Mutation)
Image 6Turing'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 7A 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 8Rhagoletis pomonella, the hawthorn fly, appears to be in the process of sympatric speciation. (from Speciation)
Image 9Gaur (Indian bison) can interbreed with domestic cattle. (from Speciation)
Image 10African pygmy kingfisher, showing coloration shared by all adults of that species to a high degree of fidelity. (from Speciation)
Image 11A red tulip exhibiting a partially yellow petal due to a mutation in its genes (from Mutation)
Image 12Homologous 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 13Selection of disease-causing mutations, in a standard table of the genetic code of amino acids (from Mutation)
Image 14Gap 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 15Types of small-scale mutations (from Mutation)
Image 16Cichlids such as Haplochromis nyererei diversified by sympatric speciation in the Rift Valley lakes. (from Speciation)
Image 17Expression of homeobox (Hox) genes in the fruit fly (from Evolutionary developmental biology)
Image 18Comparison of allopatric, peripatric, parapatric and sympatric speciation (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 20Prodryas persephone, a Late Eocene butterfly (from Mutation)
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 22Mutation with double bloom in the Langheck Nature Reserve near Nittel, Germany (from Mutation)
Image 23A gene regulatory network (from Evolutionary developmental biology)
Image 24Among 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 25Five types of chromosomal mutations (from Mutation)
Image 26Reinforcement assists speciation by selecting against hybrids. (from Speciation)
Image 27Point mutations classified by impact on protein (from Mutation)
Image 28The pax-6 gene controls development of eyes of different types across the animal kingdom. (from Evolutionary developmental biology)
Image 29Embryology 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 30Gene product distributions along the long axis of the early embryo of a fruit fly (from Evolutionary developmental biology)
Image 31Male Drosophila pseudoobscura (from Speciation)
Image 32Speciation 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)

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The Golden Toad was last seen on May 15, 1989. Decline in amphibian populations is ongoing worldwide.

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Did you know... - show different entries

... 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 American evolutionary biologist Jack Lester King co-authored a provocative 1969 paper, "Non-Darwinian Evolution", on the neutral theory of molecular evolution?
... 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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