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Convergent evolution—the repeated evolution of similar traits in multiple lineages which all ancestrally lack the trait—is rife in nature, as illustrated by the examples below. The ultimate cause of convergence is usually a similar evolutionary biome , as similar environments will select for similar traits in any species occupying the same ...
It is a complex trait because multiple genetic and environmental factors impact the phenotype. [13] [14] The phenotype before the threshold is referred to as normal or absent, and after the threshold as lethal or present. These traits are often examined in a medical context, because many diseases exhibit this pattern or similar. [9]
Pleiotropy seems limited for many traits in humans since the SNP overlap, as measured by variance accounted for, between many polygenic predictors is small. Most genetic traits are polygenic in nature: controlled by many genetic variants, each of small effect. These genetic variants can reside in protein coding or non-coding regions of the genome.
A polyphenism is the occurrence of several phenotypes in a population, the differences between which are not the result of genetic differences. [2] For example, crocodiles possess a temperature-dependent sex determining polyphenism, where sex is the trait influenced by variations in nest temperature. [3]
Analysis on quantitative trait locus effects has been used to examine the impact of directional selection in phenotypic diversification. QTL is a region of a gene that corresponds to a specific phenotypic trait, and the measuring the statistical frequencies of the traits can be helpful in analyzing phenotypic trends. [9]
Life history traits are traits closely linked to fitness, such as traits associated with growth rate, body size, stress response, timing of reproduction, offspring quantity/quality, longevity and dispersal. [6] A classic example of life history tradeoffs is a negative relationship between the age and the size of maturity.
A cline is a spatial gradient in a single specific trait, rather than in a collection of traits; [3] a single population can therefore have as many clines as it has traits, at least in principle. [4] Additionally, as Julian Huxley recognised, these multiple independent clines may not act in concordance with each other. For example, it has been ...
An example is thermo-regulation in Sauropsida, which is the clade containing the lizards, turtles, crocodiles, and birds. Lizards, turtles, and crocodiles are ectothermic (coldblooded), while birds are endothermic (warmblooded). Being coldblooded is symplesiomorphic for lizards, turtles, and crocodiles, but they do not form a clade, as ...