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Stabilizing selection (not to be confused with negative or purifying selection [1] [2]) is a type of natural selection in which the population mean stabilizes on a particular non-extreme trait value. This is thought to be the most common mechanism of action for natural selection because most traits do not appear to change drastically over time ...
Baby weighed as appropriate for gestational age. Birth weight is the body weight of a baby at their birth. [1] The average birth weight in babies of European and African descent is 3.5 kilograms (7.7 lb), with the normative range between 2.5 and 4.0 kilograms (5.5 and 8.8 lb). [2]
As of 2022, the world record for the lowest gestational age newborn to survive is held by Curtis Zy-Keith Means, who was born on 5 July 2020 in the United States, at 21 weeks and 1 day gestational age, weighing 420 grams. [5] A preterm birth, also known as premature birth, is defined as babies born alive before 37 weeks of pregnancy are ...
The first and most common function to estimate fitness of a trait is linear ω =α +βz, which represents directional selection. [1] [10] The slope of the linear regression line (β) is the selection gradient, ω is the fitness of a trait value z, and α is the y-intercept of the fitness function.
Normal weight at term delivery is 2,500–4,200 g (5 lb 8 oz – 9 lb 4 oz). [citation needed] SGA is not a synonym of low birth weight, very low birth weight, or extremely low birth weight. For example, with a 35-week gestational age delivery, a weight of 2,250 g (4 lb 15 oz) is appropriate for gestational age but is still low birth weight.
Selection coefficient, usually denoted by the letter s, is a measure used in population genetics to quantify the relative fitness of a genotype compared to other genotypes. . Selection coefficients are central to the quantitative description of evolution, since fitness differences determine the change in genotype frequencies attributable to selecti
A ratio greater than 1 implies positive or Darwinian selection (driving change); less than 1 implies purifying or stabilizing selection (acting against change); and a ratio of exactly 1 indicates neutral (i.e. no) selection.
[1] The maneuvers consist of four distinct actions, each helping to determine the position of the fetus. The maneuvers are important because they help determine the position and lie of the fetus , which in conjunction with correct assessment of the shape of the maternal pelvis can indicate whether the delivery is going to be complicated, or ...