Developmental biology studies embryonic and other developmental processes
Embryology is a key subdiscipline of developmental biology
Embryonic development towards adult form is not linear
A single fertilized cell develops into all of the cells in the individual
Cells in embryos can direct their fate based on positional cues and instructions in their genes
Embryos build themselves progressively through development
Basic Principles of Development:
Cleavage: Cell Division in multicellular organisms
Gastrulation: Formation of 3 Germ layers
Organogenesis: Cell differentiation into Blood, Muscle, Nerves, etc.
Growth: Maturity
Morphogenesis or Developmental Mechanics: Involves Cell adhesion, shape, movement, proliferation/death, and extracellular materials
Developmental events are controlled by differential gene expression
Major developmental defects occur in approximately 3% of live births
Developmental biology is the study of the process by which organs grow and develop
Developmental biology studies genetic control of cell growth, differentiation, and morphogenesis
Developmental biology is the causal analysis of cellular mechanisms driving growth, pattern formation, and morphogenesis
Developmental biology studies how animals and plants grow and develop, synonymous with ontogeny
Questions in developmental biology revolve around understanding biochemical changes during physiological transitions between developmental stages
Developmental Biology is defined by questions of Differentiation, Morphogenesis, Growth, Reproduction, Evolution, and Environmental Integration
Differentiation involves the development of a single, pluripotent cell into a complete organism
Morphogenesis studies how differentiated cells move and reorganize to generate functional organisms
Growth questions the limiting factors for cell division and rates of mitosis in embryos
Reproduction involves gametogenesis and interaction of gametes at fertilization
Evolution studies the evolutionary relationships between groups of organisms
Environmental Integration shows how early development of organisms is influenced by environmental cues
Comparative Embryology, Evolutionary Embryology, Teratology, and Mathematical Modeling contribute to the study of development
Early "Embryologists" like Aristotle, William Harvey, and Marconi Malpighi made significant contributions to embryology
Aristotle considered basic developmental questions about the existence and growth of developing organisms
Aristotle discussed Epigenesis versus Preformation in embryonic development
Preformation theory suggests the organism is preformed in the sperm or egg and grows larger, while Epigenesis theory states the organism develops in a stepwise fashion from an unorganized state
Aristotle believed the embryo was formed from menstrual blood interacting with a male factor present in the semen
Aristotle believed that the embryo was formed from the menstrual blood interacting with a male factor in the semen
His observations supported the concept of epigenesis
Malpighi found embryonic structures in unincubated eggs left in the warm sun of southern Italy during the summer months
Malpighi's observations spurned the preformationist ideas
Preformationists believed in tiny preformed beings present in the gamete, with even tinier beings within their embryonic germ cells
Nicolas Hartsoeker, a Dutch mathematician and physicist, was a spermist preformationist
Charles Bonnet, a Swiss philosopher, was an Ovist preformationist
William Harvey, physician to King Charles I of England, explained blood circulation and published Essays on the Generation of Animals
Rene Descartes, a philosopher, introduced the famous phrase "Cogito ergo sum"
Pierre Maupertuis, a French mathematician and biologist, introduced the theory of survival of the fittest
Christian Pander visualized epigenesis of embryonic germ layers
Ernst von Baer described the notochord, discovered the mammalian egg, and proposed 4 laws of development
Heinrich Rathke described pharyngeal arches and skull formation