The Embryo Project Encyclopedia (https://embryo.asu.edu) is an open-access digital encyclopedia devoted to recording and contextualizing the science of embryos, development, and reproduction. The collection of documents, images, and multimedia housed here serves as the Encyclopedia's permanent archive.

Jane Maienschein, ASU University Professor, Regents Professor, and Director of the Biology and Society Program, started the Embryo Project Encyclopedia in 2007 with support from the National Science Foundation.

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Wilhelm Johannsen in Denmark first proposed the distinction between genotype and phenotype in the study of heredity in 1909. This distinction is between the hereditary dispositions of organisms (their genotypes) and the ways in which those dispositions manifest themselves in the physical characteristics of those organisms (their phenotypes). This distinction

Wilhelm Johannsen in Denmark first proposed the distinction between genotype and phenotype in the study of heredity in 1909. This distinction is between the hereditary dispositions of organisms (their genotypes) and the ways in which those dispositions manifest themselves in the physical characteristics of those organisms (their phenotypes). This distinction was an outgrowth of Johannsen's experiments concerning heritable variation in plants, and it influenced his pure line theory of heredity. While the meaning and significance of the genotype-phenotype distinction has been a topic of debate-among Johannsen's contemporaries, later biological theorists, and historians of science-many consider the distinction one of the conceptual pillars of twentieth century genetics. Moreover some have used it to characterize the relationships between studies of development, genetics, and evolution.

Created2012-12-07
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Richard Woltereck was a German zoologist and hydrobiologist who studied aquatic animals and extended the concept of Reaktionsnorm (norm of reaction) to the study of genetics. He also provided some of the first experimental evidence for the early twentieth-century embryological theory of heredity known as cytoplasmic inheritance. Through experiments on

Richard Woltereck was a German zoologist and hydrobiologist who studied aquatic animals and extended the concept of Reaktionsnorm (norm of reaction) to the study of genetics. He also provided some of the first experimental evidence for the early twentieth-century embryological theory of heredity known as cytoplasmic inheritance. Through experiments on the water flea, Daphnia, Woltereck investigated whether variation produced by environmental impacts on development could play a role in heredity and evolution. Woltereck's research emphasized the importance of environment and development in Wilhelm Johannsen's concepts of genotype and phenotype. Biologists throughout the twentieth century used Woltereck's concept of Reaktionsnorm to develop theories and experiments to explain the evolution of adaptive developmental responses to environmental conditions. Later in his career, Woltereck developed a theory of heredity that sought to reconcile embryological concepts, such as regulation and body plans, with Mendelian heredity and Darwinian evolution by natural selection.

Created2012-05-13
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Richard Woltereck first described the concept of Reaktionsnorm (norm of reaction) in his 1909 paper 'Weitere experimentelle Untersuchungen uber Art-veranderung, speziell uber das Wesen quantitativer Artunterschiede bei Daphniden' ('Further investigations of type variation, specifically concerning the nature of quantitative differences between varieties of Daphnia'). This concept refers to the ways

Richard Woltereck first described the concept of Reaktionsnorm (norm of reaction) in his 1909 paper 'Weitere experimentelle Untersuchungen uber Art-veranderung, speziell uber das Wesen quantitativer Artunterschiede bei Daphniden' ('Further investigations of type variation, specifically concerning the nature of quantitative differences between varieties of Daphnia'). This concept refers to the ways in which the environment can alter the development of an organism, and its adult characteristics. Woltereck conceived of the Reaktionsnorm as the full range of potentialities latent in a single genotype, evocable by the environmental circumstances of a developing organism. Biologists used variants of Woltereck's concept of Reaktionsnorm, often called the reaction norm or norm of reaction, throughout the twentieth century in attempts to explain how developmental responses to the environment can evolve, and even alter the tempo and direction of evolutionary change.

Created2012-09-06