Portal:Evolutionary biology

Image 1The 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 2The pax-6 gene controls development of eyes of different types across the animal kingdom. (from Evolutionary developmental biology)

Image 3A. 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 4Gaur (Indian bison) can interbreed with domestic cattle. (from Speciation)

Image 5Among 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 6Cichlids such as Haplochromis nyererei diversified by sympatric speciation in the Rift Valley lakes. (from Speciation)

Image 7Five types of chromosomal mutations (from Mutation)

Image 8Speciation 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 9A gene regulatory network (from Evolutionary developmental biology)

Image 10Homologous 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 11Embryology 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 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 14Expression of homeobox (Hox) genes in the fruit fly (from Evolutionary developmental biology)

Image 15African pygmy kingfisher, showing coloration shared by all adults of that species to a high degree of fidelity. (from Speciation)

Image 16Gene product distributions along the long axis of the early embryo of a fruit fly (from Evolutionary developmental biology)

Image 17Dutch botanist Hugo de Vries making a painting of an evening primrose, the plant which had apparently produced new forms by large mutations in his experiments, by Thérèse Schwartze, 1918 (from Mutation)

Image 18The 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 19Gap 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 20A 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 21A covalent adduct between the metabolite of benzo[a]pyrene, the major mutagen in tobacco smoke, and DNA (from Mutation)

Image 22Prodryas persephone, a Late Eocene butterfly (from Mutation)

Image 23Comparison of allopatric, peripatric, parapatric and sympatric speciation (from Speciation)

Image 24Phyletic 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 25Selection of disease-causing mutations, in a standard table of the genetic code of amino acids (from Mutation)

Image 26Male Drosophila pseudoobscura (from Speciation)

Image 27Rhagoletis pomonella, the hawthorn fly, appears to be in the process of sympatric speciation. (from Speciation)