One of the large multinuclear cells in growing bones concerned with bone resorption (dissolution and absorption of osseous tissue). They have 5 to 20 nuclei, but some may have as many as 200 nuclei), and were discovered by Rudolf Albert von Kolliker (1817-1905) in 1873. Due to their role in bone resorption, they are crucial …
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Orthography
A standardized system of writing (or script) for a particular language about how letters are used to express sounds and words, as well as including rules for spelling words. Orthography for English was not standardized until Shakespeare’s time, which reduced the number of words with different spellings. Individuals such as George Bernard Shaw (1856-1950) and …
Orthogonality
In has two features: 1. a characteristic of ANOVA designs in which there are equal numbers of cases in each cell, and 2. independence of effects that are specified in a design matrix. See Analysis of variance, Balanced (or orthogonal) design, Design matrix
Orthographic reading skills
A set of skills that include the ability to read words directly without translating them to sound, usually with automaticity. In fact, they involve acquiring the ability to identify patterns of specific letters as words, eventually giving rise to word recognition. There is a unification among spelling, pronunciation and meaning of a word, such information …
Orthogenetic principle
Derived from embryology by Heinz Werner (1890-1964), he describes it as follows: ” … that wherever development occurs it proceeds from a state of relative globally and lack of differentiation to a state of increasing differentiation, articulation and hierarchic integration.” [Werner, 1957, in Harris, D.B. (Ed.), The concept of development. Minnesota: University of Minnesota Press, p. 126]. …
Organizer (embryology)
Any part of an embryo capable of inducing another part to differentiate. Frequently mentioned examples of an organizer are the dorsal lip of the blastopore and Hensen’s node. It was Hans Spemann ((1869-1941) who identified the dorsal lip as the organizer, together with his graduate student Hilde Mangold (1898-1924), for which he received the Nobel …
Organogenesis
Formation of an organ through the assembly of tissues of different kinds once the three germ layers (viz., ectoderm, entoderm, mesoderm) have been established. Many organs consist of cells from more than one germ layer. During organogenesis, some cells undergo long migrations to their final location from their place of origin. They include precursors of …
Organization
A complex and non-random set of relationships among components of a system, which are functional, spatial and temporal in nature. Unlike order, it is a physical attribute of a system and not subject to the law of entropy. See Complex system, Entropy, General system theory (GST), Order, System
Organism-environment mutualism
Having assumed the status of a principle in the ecological psychology of James J. Gibson (1904-1979), it holds that animal and environment, as well as perception and action, are yoked by the two fundamental reciprocities that function in distinct, but complementary ways a reciprocity between internal and external frames of references (i.e., between internal and external …
Organism
Any living thing, including plants and animals, having the ability to act or function independently. It is composed of different organs or parts with functions that are separate, but mutually independent, and essential to the life of the individual. See Adaptation, Character, Constitution, Embryology, Function, Mutant, Mutation (biology), Ontogenetic development, Organism-environment mutualism