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Phenotypic variation (due to underlying heritable genetic variation) is a fundamental prerequisite for evolution by natural selection. It is the living organism as a whole that contributes (or not) to the next generation, so natural selection affects the genetic structure of a population indirectly via the contribution of phenotypes.
Examples of human phenotypic variability: people with different levels of skin colors, a normal distribution of IQ scores, the tallest recorded man in history - Robert Wadlow - with his father. Human variability, or human variation, is the range of possible values for any characteristic, physical or mental, of human beings.
Plants display the most obvious examples of ecophenotypic variation. One example are trees growing in the woods developing long straight trunks, with branching crowns high in the canopy, while the same species growing alone in the open develops a spreading form, branching much lower to the ground.
Genetic variation can be identified at many levels. Identifying genetic variation is possible from observations of phenotypic variation in either quantitative traits (traits that vary continuously and are coded for by many genes, e.g., leg length in dogs) or discrete traits (traits that fall into discrete categories and are coded for by one or a few genes, e.g., white, pink, or red petal color ...
A phenotypic trait is an obvious, observable, and measurable characteristic of an organism; it is the expression of genes in an observable way. An example of a phenotypic trait is a specific hair color or eye color. Underlying genes, that make up the genotype, determine the hair color, but the hair color observed is the phenotype.
Genetic architecture is the underlying genetic basis of a phenotypic trait and its variational properties. [1] Phenotypic variation for quantitative traits is, at the most basic level, the result of the segregation of alleles at quantitative trait loci (QTL). [2]
Similar genotypic changes may result in similar phenotypic alterations, even across a wide range of species. [1] The genotype–phenotype distinction is drawn in genetics. The "genotype" is an organism's full hereditary information. The "phenotype" is an organism's actual observed properties, such as morphology, development, or behavior.
V P = V E + V G, where the terms refer to variation in phenotype, environment, and genotype respectively. [1] Broad sense heritability (H 2, or H B) refers to the phenotypic differences arising from all genetic effects, and can be described as the ratio of genotypic variation to that of phenotypic variation in the population, or: H 2 = V G / V P.