Polygenic traits occur because of genes and environment. There are usually two or more genes involved in these traits. It also takes into consideration where the organism lives, for example the fact that some hotter areas have a history of people with darker skin tones.
Traits and selctive breeding are related in that during selective breeding you have to choose from traits form you and your partner. the traits you have may be passes through selctive breeding.
Without going into a long and technical discussion of the population genetics of polygenic vs. simplex traits, one could simply say that they're affected in much the same way: the frequency of some traits is reduced, while the frequency of other traits is increased, regardless of whether they're polygenic in nature or simplex.
There is a noteworthy difference, however: simplex traits may be eradicated from the population gene pool entirely, if they have no essential secondary function. But in most complex traits it's much more likely that one or more of the genes involved has some secondary function, or that the complex is interlinked in such a way that removal of a part or the whole would leave a disabled organism. Height, for instance, can be considered a trait, but is really a variation in the way a developing organism, under influence of many genetic factors, grows. You cannot eliminate "short" from the population without affecting the genes that make growth possible at all.
Another complication is that polygenic traits usually come in a spectrum of variations. For instance, one could regard height as a single trait with many possible values, ranging from "short" to "long". In such cases, one could distinguish three ways that natural selection might act on the trait:
Directional selection occurs when phenotypes at one end of the spectrum lead to greater survival and/or reproduction. Stabilizing selection occurs when phenotypes in the middle range confer greater survival/reproduction, while phenotypes at both extremes lead to decreased fitness. Disruptive selection is the least common of the three types and occurs when phenotypes at both endsof the spectrum lead to greater survival and reproduction, while phenotypes in the mid range are a disadvantage.
A single additional observation may be of interest: it's possible that natural selection favours a polygenic trait in which one of the genetic components has a detrimental impact - the benefits of the complex entire may outweigh the detrimental impact of the single component gene.
It could give the offspring a trait that the scientist doing the selective breeding dont want the offspring to have.
no, inherited traits are responsible for natural selection
When nothing happens to exert strong population pressure on that population, natural selection favors the allele frequency already present. When mutations cause new traits, natural selection weeds these traits out because they're not as efficient as the others.
Yes, a single gene can affect many traits. this is called plieotropy
Variation naturally occurs in populations as new traits arise from random mutations. However, through natural selection only those traits that are beneficial to the organism are passed on to the next generation. Any harmful mutations are naturally weeded out.
This type of natural selection is called stabilizing selection because the mean traits of the population are being selected for against the immediate environment.
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Polygenic? Natural selection usually acts on the phenotype of polygenic traits as they are suites of genes acting in concert to form a trait. If you had a trait, such as height, in two variant brothers then the aggregate would need to be selected for as the genes working in concert, but not equally well, would render different heights in the brothers which would be then visible to natural selection.
How does natural selection affect undesirable traits?
Traits that are produced by the interaction of several genes are called polygenic traits. Examples of polygenic traits are height and skin color.
Polygenic Traits
Polygenic Traits.
One pattern of natural selection polygenic traits is directional selection, in which one end of the spectrum leads to increased fitness and the other end decreased fitness. Disruptive selection is when both ends of the spectrum lead to increased fitness and the middle leads to decreased fitness and it leads to two distinct phenotypes being selected for. It's opposite is stabilizing selection, in which the middle has the best fitness and the two extremes have decreased fitness.
No. Natural selection is the differential reproductive success of varying inherited traits. Acquired traits do little to affect the inheritance of traits, except through epigenetics.
no, inherited traits are responsible for natural selection
When nothing happens to exert strong population pressure on that population, natural selection favors the allele frequency already present. When mutations cause new traits, natural selection weeds these traits out because they're not as efficient as the others.
Humans directly affect artificial selection. They do this by selecting the specific traits that they prefer which they cannot don in a natural selection.
Natural selection and artificial selection both involve an organism's traits being determined by how much they're favored. Then, the organisms with favorable traits pass those traits on to future generations.However, natural selection is caused by survival; the organisms with traits that increase their chances for survival and reproduction pass on their traits. As for artificial selection, humans purposefully decide which traits (like the most colorful one) of an organism to pass on.The similarity of artificial selection and natural selection is that they both can cause changes in the frequency of population.