A description of the life history of the typical individual of a particular species from a zygote to sexual maturity. Ontogenesis is sometimes used interchangeably, but at other times taken to refer to the life history of a particular individual. See Development, Evolutionary biology, Jacob-Monod operon model, Ontogenetic adaptation, Ontogenetic development, Ossification, Phylogeny, Recapitulation theory …
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Ontogenetic development
Concerns identifying the processes and mechanisms of change during species-characteristic ontogeny. Change involves accounting for the transitions between a succession of states or attractors, an issue addressed by dynamical systems approaches such as catastrophe theory. In addition to the change problem, there is also the origin problem: events that predispose or prepare a developing organism …
Ontogenetic adaptation
An anatomical, physiological or behavioral characteristic that serves a transient, age-specific, biological function during development, and which may occur relatively independently of experience. It may be appropriate for survival during one phase of development (e.g., during prenatal life), but unnecessary or even incompatible with adaptations required for later phases. As a consequence, they must be eliminated, suppressed …
On-line emergence
The emergence of linguistic patterns during the process of conversation and listening. In fact, it is a phenomenon that occurs during a wide range of developmental change. According to one attempt at explanation. new forms of expression as a process of computational manipulations of symbols produce universal and orderly stage-like patterns of change in language …
Oligohydramnios
Reduced volume of amniotic fluid, expected for gestational age, that surrounds the fetus. It is the opposite of another pregnancy complication, namely, hydramnios. Too little fluid for an extended period of time can result in abnormal physical and behavioral development. The amount of fluid is derived from ultrasound examination, the most common measurement being the amniotic …
Oligosaccharides
Essential structural components of living cells and source of energy, which include simple sugars (monosaccharides) with small molecules as well as macromolecular substances. They are carbohydrates formed by joining together monosaccharide units in a chain. They are classified according to the number of monosaccharide groups they contain. See Adhesion molecules, Cell, Cell adhesion molecules (CAMs), …
Oligogenic mode of inheritance
Inheritance pattern requiring the influence of a few (two or three) genes. Previously, diseases regarded as monogenic have in recent years been revealed as the product of by an additional gene or genes, and such diseases have been now classified as ‘oligogenic’ rather than ‘polygenic’, as they involve a relatively smaller number of genes. One …
Olfaction
The sense of smell based on the detection and identification of airborne chemicals referred to odorants. These chemical compounds are volatile, small and hydrophic, and when inhaled are transported to the olfactory epithelium (or regio olfactoria) located in the roof of the two two nasal cavities. It appears that some 95% of the nasal cavity …
Oligodendrocytes
Neuroglia responsible the manufacture the myelin sheath that insulates and supports axons in most vertebrates (only jawless fish such as hagfish and lampreys do not have oligodendrocytes, but they are absent in the retina of humans, mice and rats). In the peripheral nervous system, this function resides with Schwann cells. Oligodendrocytes are not only found …
Oedipal complex
The stage of development hypothesized by Sigmund Freud in his book The interpretation of dreams (1899) in which a boy, at around 3-5 years of age, falls in love with his mother, has an unconscious desire to have sex with her, but fears castration by his father. The female analogue is the Electra complex as …