Developmental Processes - History, Evolutionary Aspects, Information Transfer, Growth, Differentiation
cells organisms embryo pattern
Developmental processes are the series of biological changes associated with information transfer, growth, and differentiation during the life cycle of organisms. Information transfer is the transmission of DNA and other biological signals from parent cells to daughter cells. Growth is the increase in size due to cell expansion and cell division. Differentiation is the change of unspecialized cells in a simple body pattern to specialized cells in more complex body pattern. While nearly all organisms, even single-celled bacteria, undergo development of some sort; the developmental process of complex multicellular organisms is emphasized here. In these organisms, development begins with the manufacture of male and female sex cells. It proceeds through fertilization and formation of an embryo. Development continues following birth, hatching, or germination of the embryo and culminates in aging and death.
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Until the mid-1800s, many naturalists supported a theory of development called epigenesis, which held that the eggs of organisms were undifferentiated, but had a developmental potential which could be directed by certain external forces. Other naturalists supported a theory of development called preformationism, which held that the entire complex morphology of mature organism is present in miniatu…
People have long been interested in the connection between the development of an organism, its ontogeny, and the evolutionary ancestry of the species, its phylogeny. Anaximander, a philosopher of ancient Greece, noted that human embryos develop inside fluid-filled wombs and proposed that human beings evolved from fish as creatures of the water. This early idea was a progenitor to recapitulation th…
Nearly every multicellular organism passes through a life cycle stage where it exists as a single undifferentiated cell or as a small number of undifferentiated cells. This developmental stage contains molecular information which specifies the entire course of development encoded in its many thousands of genes. At the molecular level, genes are used to make proteins, many of which act as enzymes, …
Organisms generally increase in size during development. Growth is usually allometric, in that it occurs simultaneously with cellular differentiation and changes in overall body pattern. Allometry is a discipline of biology which specifically studies the relationships between the size and morphology of an organism as it develops and the size and morphology of different species. A developing organi…
Differentiation is the change of unspecialized cells in a simple body pattern to specialized cells in a more complex body pattern. It is highly coordinated with growth and includes morphogenesis, the development of the complex overall body pattern. Below, we emphasize molecular changes in organisms which lead to development. However, this does not imply that external factors have no role in develo…
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