History Of Developmental Biology PDF

HISTORY OF DEVELOPMENTAL BIOLOGY HISTORICAL BACKGROUND Embryology - descriptive study of development. 1. Aristotle (340 BC) Developmental Biology - study of...

HISTORY OF DEVELOPMENTAL BIOLOGY HISTORICAL BACKGROUND Embryology - descriptive study of development. 1. Aristotle (340 BC) Developmental Biology - study of Observed that new structures arose processes and mechanisms behind progressively in embryos (e.g. development; mostly experimental. blood, blood vessels, heart, blood Phylogenetic development - gradual vessels around organs). evolutionary history of a species. Supported epigenesis in 17th Ontogenetic development - transformation century of an organism within its own lifetime. Believed that the embryo was formed from menstrual blood PHASES OF ONTOGENETIC DEVELOPMENT interacting with a male vital factor Gametogenesis present in the semen. This creative Fertilization force forms the maternal substance Cleavage into embryonic body parts. Gastrulation 2. Bonnet & Swammerdam (17th century) Organogenesis Preformation Theory: embryonic Growth and Histological Differentiation parts are already present in the Metamorphosis/Regeneration sperm of egg (aminalculists or ovists) DEVELOPMENTAL BIOLOGY UNITES THE Leeuenhoek and other early DISCIPLINES OF MOLECULAR/CELLULAR microscopists claimed to have seen BIOLOGY, GENETICS, AND MORPHOLOGY the homunculus. Molecular and cell biology - tells us about 3. Caspar Friedrich Wolff (1759) how individual genes and cells work. Postulated that a development force Genetics - tells us directly about the inherent in the matter of the embryo function of an individual gene and how it directs the laying down of body relates to the activities of other genes. parts in sequence. Morphology - basis on which further Laid the foundation for the Germ rounds of signaling and responses can Layer Theory by showing that the occur, creating a progressively more material out of which the embryo is complex morphology. constructed is, in an early stage of development, arranged in the form Development DOES NOT happen by magic. Information and of leaf-like layers. mechanisms at the cellular and/or molecular levels are 4. Karl Ernst von Baer (1828) needed to accomplish development. Most coherent embryological data. Baer’s Law: more general features that are common to all members of groups of animals are developed in the embry earlier than the more special features which distinguish  the members of the group (e.g. 8. H. Driesch (1891), Endres (1895), vertebrates develop earlier than Spemann (1901), Schmidt (1903) hair, feathers, limbs). Regulative model of development - 5. Fritz Muller (1864), Ernst Haeckel (1868) if cleavage cells of a sea urchin were Biogenetic law: features inherited completely separated, each develop from the common ancestor of the into a whole embryo group have an ancient origin; develop earliest during ontogeny. Recapitulation Theory: the development of individual organisms (ontogeny) follows the same phases of the evolution of larger ancestral groups. 6. August Weismann (1883) 9. T.H. Morgan (1919), Watson & Crick Germ Plasm Theory: every germ cell (1953) during early development receives a Units of heredity composed of complete set of units of heredity. sequences of DNA base triplets are Development involves orderly transformed into an array of unpacking of an embryo proteins. Each egg nucleus contains discrete localized determinants which result in unequal distribution of nuclear components. Mosaic model of development - cells cannot change their fate if a blastomere is lost. 7. Wilhelm Roux (1905) Heat-killed one of the 2 blastomeres of a frog’s egg. Results either support both preformation and mosaic development or crude techniques.