What's the difference between heterochrony and variation?
Heterochrony
Definition:
(n.) In evolution, a deviation from the typical sequence in the formation of organs or parts.
Example Sentences:
(1) A detailed analysis of the frontal, medial prefrontal and hippocampal regions also shows a heterochrony within these regions.
(2) These groups correspond to different stages of neuroblast development in vivo and their presence in the tissue cultures of different brain regions reflects the heterochrony of cell development in these regions.
(3) Direct development is achieved primarily by heterochrony, that is, by the abbreviation or elimination of larval developmental processes and the acceleration of processes involved in development of adult features.
(4) Ontogeny in the tube-crested dinosaur Parasaurolophus (Hadrosauridae) and heterochrony in hadrosaurids.
(5) The concepts of chronogenetics, heterochrony, and developmental field defects appear relevant to yet another set of patients with chromosome anomalies.
(6) It has been pointed out, that there is a complex heterochrony of regional development in the brain.
(7) Certain single malformations such as holoprosencephaly immediately suggest heterochrony by their resemblance to antecedent phylogenetic or embryologic structures.
(8) Some male sterile mutations can decouple the development of the different components of a germ cell, i.e., they may lead to a heterochrony of the development of the different subcellular structures, or they may permit the differentiation of some components of a germ cell even in the complete absence of an organelle.
(9) He has only mentioned the concept of heterochrony to which we give much more importance nowadays.
(10) The role of altered developmental timing or heterochrony in morphologic evolution has intrigued classical and modern biologists.
(11) During prenatal life of monkey and man in the development of the frontal area the phenomena of heterochrony (common for both species) and anabolia (peculiar for man only) are observed (the appearance of new more complex structures).
(12) It is theorized that hormones are a major factor in the non-random regulation of cellular heterochrony in tumourigenesis.
(13) The data obtained suggest a heterochrony and different rate of the functional callosal connexions maturation in projection and associative areas of the cortex.
(14) The perspective of heterochrony stresses the molecular history and hierarchy which is recapitulated with each pregnancy, and reconciles apparent discrepancies between the rates of molecular and morphologic evolution.
(15) In terms of heterochrony such a pattern most likely is the result of a process termed "acceleration", i.e.
(16) Notwithstanding this, gross regularities of heterochrony in the neurogenetic behavior of the different segments lead to a definition of elemental longitudinal compartments of the forebrain and mesencephalon (floor, paramedian, basal, and alar regions) on the basis of precocious differentiation of the basal region and retarded differentiation of the paramedian and alar regions.
(17) Molecular mechanisms underlying heterochrony are thereby described.
(18) We propose that such a shift in relative timing of the developmental phenomena involved inhibits pigment cell migration in embryos of the white axolotl mutant and, accordingly, that the restricted pigmentation of the mutant larva is generated through heterochrony.
(19) In its normal ontogeny, Hydractinia symbiolongicarpus, a closely related hydractiniid hydroid, not only shows morphological heterochrony similar to that induced in P. carnea by DNP, but also shows a pattern of gastrovascular flow similar to that observed in P. carnea under treatment with DNP.
(20) In view of elucidating the origin of this heterochrony, we make an electrophoretic study of the different extracts from juveniles, adults in activity, in natural sleep and awakning.
Variation
Definition:
(n.) The act of varying; a partial change in the form, position, state, or qualities of a thing; modification; alternation; mutation; diversity; deviation; as, a variation of color in different lights; a variation in size; variation of language.
(n.) Extent to which a thing varies; amount of departure from a position or state; amount or rate of change.
(n.) Change of termination of words, as in declension, conjugation, derivation, etc.
(n.) Repetition of a theme or melody with fanciful embellishments or modifications, in time, tune, or harmony, or sometimes change of key; the presentation of a musical thought in new and varied aspects, yet so that the essential features of the original shall still preserve their identity.
(n.) One of the different arrangements which can be made of any number of quantities taking a certain number of them together.
Example Sentences:
(1) The variation in thickness of the LLFL may modulate the species causing damage to the cells below it.
(2) There was appreciable variation in toothbrush wear among subjects, some reducing their brush to a poor state in 2 weeks whereas with others the brush was rated as "good" after 10 weeks.
(3) Correction for within-person variation in urinary excretion increased this partial correlation coefficient between intake and excretion to 0.59 (95% CI = 0.03 to 0.87).
(4) The coefficient of variation in the integrated area of a single peak is 16%.
(5) Sequence variation in the gp116 component of cytomegalovirus envelope glycoprotein B was examined in 11 clinical strains and compared with variation in gp55.
(6) Effects of habitual variations in napping on psychomotor performance, short-term memory and subjective states were investigated.
(7) A small variation in T1 was found between older (greater than 40 years) and younger (less than 40 years) subjects, but no such effect was observed in the case of T2.
(8) The variation of the activity of the peptidase with pH in the presence of various inhibitors was investigated in both control and insulted muscle fibres.
(9) This study examined both the effect of variations in optical fiber tip and in light wavelength on laser-induced hyperthermia in rat brain.
(10) = 19) with a very low, but statistically significant, correlation with the AUC, r = 0.35 (p less than 0.05), thus demonstrating a very great individual variation in sensitivity to cimetidine.
(11) Once the normal variations are mastered, appreciation of retinal, choroidal, optic nerve, and vitreal abnormalities is possible.
(12) Regression analysis on the 21 clinical or laboratory parameters studied showed that the only variable independently associated with CSF-FN was the total protein concentration in the CSF; this, however, explained only 14% of the observed variation in the CSF-FN concentration and did not show any correlation with CNS involvement.
(13) Pharmacokinetic parameters, such as these clearances, had large intersubject variations.
(14) Variability (CV = 0.7%) in body volume of a 45-year-old reference man measured by SH method was very similar to variation (CV = 0.6%) in mass volume of the 60-1 prototype.
(15) Further analysis of the role of sex steroid hormones is required in view of the sex variations reported.
(16) The overall result of this system has been to decrease the coefficients of variation to below 5% for all the milk and serum proteins tested.
(17) The variation in age-specific rates with age was similar for all cancers, as demonstrated by large positive correlation coefficients between age-incidence patterns averaged over all populations.
(18) Even though there are variations among equipment bearing the same model number it was considered worthwhile to make available relative cavitational and temperature data.
(19) Accordingly, LPA proved an extremely stable characteristic which did not show any substantial variations in the course of five years.
(20) Variation in patient mix was a major determinant of the large variations in resource use.