The Origin of Birds is an early synopsis ofbird evolution written in 1926 byGerhard Heilmann, aDanish artist and amateurzoologist. The book was born from a series of articles published between 1913 and 1916 in Danish, and although republished as a book it received mainly criticism from established scientists and got little attention within Denmark. The English edition of 1926, however, became highly influential at the time due to the breadth of evidence synthesized as well as the artwork used to support its arguments. It was considered the last word on the subject of bird evolution for several decades after its publication.
Through the course of the research represented in the book, Heilmann considers and eventually rejects the possibility of all living and several extinct groups ofreptiles as potential ancestors for modern birds, includingcrocodilians,pterosaurs and several groups ofdinosaurs. Despite his acknowledgment that some of the smallerJurassictheropods had many similarities toArchaeopteryx and modern birds, he determined that they were unlikely to be direct bird ancestors and that they were instead closely–related offshoots, and concluded that the similarities were a result ofconvergent evolution rather than direct ancestry. Based essentially on a process of elimination, Heilmann arrives at the conclusion that birds must be descended fromthecodonts, a group ofarchosaurs that lived during thePermian andTriassic periods. Although this conclusion was later shown to be inaccurate,The Origin of Birds was regarded as a masterful piece of scholarship at the time and set the international agenda for research in bird evolution for nearly half a century, and much of its research remains of interest. (Full article...)
Image 2The distribution of fitness effects (DFE) of mutations invesicular stomatitis virus. In this experiment, random mutations were introduced into the virus by site-directed mutagenesis, and thefitness 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. (fromMutation)
Image 4This figure shows a simplified version of loss-of-function, switch-of-function, gain-of-function, and conservation-of-function mutations. (fromMutation)
Image 9A mutation has caused thismoss rose plant to produce flowers of different colours. This is asomatic mutation that may also be passed on in thegermline. (fromMutation)
Image 10Speciation via polyploidy: Adiploid cell undergoes failedmeiosis, producing diploidgametes, which self-fertilize to produce a tetraploidzygote. In plants, this can effectively be a new species, reproductively isolated from its parents, and able to reproduce. (fromSpeciation)
Image 15Gap genes in the fruit fly are switched on by genes such asbicoid, setting up stripes across the embryo which start to pattern the body's segments. (fromEvolutionary developmental biology)
A complete list of scientific WikiProjects can be foundhere. See alsoWikispecies, a Wikimedia project dedicated to classification of biological species.
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![Image 8A covalent adduct between the metabolite of benzo[a]pyrene, the major mutagen in tobacco smoke, and DNA (from Mutation)](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aBenzopyrene_DNA_adduct_1JDG.png)
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