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Bottleneck And Founder Effect

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Last Updated: 02 July 2021

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Genetic drift is a random process of alleles being passed from parents to offspring. Increasing genetic diversity in the population requires introducing a greater number of alleles, which can only occur through mutations or addition of unrelated members to the population. Genetic drift only affects how already - existing alleles are passed down. If an allele has high frequency at baseline, chance of it being passed down to subsequent generations is higher than alleles of lower frequency. Through random chance, high - frequency alleles can eventually have a frequency of 100%, becoming fixed in the population. Conversely, low - frequency allele can eventually disappear from the population if none of the few parents who possess that allele happen to pass it onto their offspring. Genetic drift describes random selection of alleles that are passed from one generation to the next due to independent assortment in gametogenesis. Genetic drift cannot create new alleles, so it cannot increase genetic diversity. It can, however, decrease genetic diversity if allele of low frequency is not passed down to subsequent generations due to pure chance. There is no hard and fast rule for whether genetic drift or natural selection have had greater effect on shaping populations. Both have greatly shaped populations present on Earth today, but their relative importance varies between species and has also varied over time. Conditions of the Hardy - Weinberg equilibrium require that both natural selection and genetic drift be negligible. If genetic drift is occurring, then the population cannot be in Hardy - Weinberg equilibrium. Bottleneck effect is a term used to describe loss of genetic variation that occurs after outside forces destroy most of the population. Few individuals leave to reproduce and pass their traits on to all of their offspring, which then may thrive without competition of large population. Eventually, there may be large, very genetically similar population based on the traits of a few original survivors. Founder effect describes low genetic variation of population derived from small groups of individuals in new geographic location. Genetic drift is random change of allele frequency in the population. The Bottleneck effect describes a phenomenon when the population has a sudden reduction in gene pool due to natural environmental events, natural disasters, disease, or human involvement. This reduction in gene pool will likely cause bias that did not exist in the original population. For example, suppose the population of birds has small numbers with mutations making them unable to fly. If a disease reaches this population that kills all birds when they reach altitude above 50m, then the gene pool of the population will suddenly shift to favor flightless birds. Bottleneck effect, after a long time, could potentially lead to speciation, but this is not the defining factor of effect. Introducing new species can increase pressures of natural selection, but does not directly relate to the bottleneck effect.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Founder Events

Imagine you have a jar containing three different colors of marbles: red, yellow and green. If you pick just two or three marbles out of a jar, it's possible you might pick all yellow and red just by chance. If different colors of marbles were different genes and the three marbles you pick were new population, new population would have only red and yellow genes but no green ones - and that's very similar to the way founder events affect genetic variation. When a small group separates from the larger population and strikes out on its own, that small group might be carrying genes that are rare in the original population. These rare genes will now be common among the new group's descendants. Other genes present in the original population, however, may be absent from the new group altogether. Huntington's Disease, for example, is more common among the Afrikaner or Dutch - descent population of South Africa than in most other populations, because genes for Huntington's happen to be unusually common among a small group of original Dutch colonists.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

SARRACENIA PURPUREA L.

Genus Sarracenia L. Belongs to the carnivorous family Sarraceniaceae, which is thought to have had interesting radiation and comprises nine well - recognized species originating in North America. Sarracenia purpurea is the only species of genus not restricted to the south of the continent, probably because of its preference for cool conditions and its outstanding tolerance to frost. This species has expanded its range, phenomenon probably linked to post - glacial recolonization and is present naturally along the whole Atlantic seaboard of North America, stretching from Florida to the boreal zone. Sarracenia purpurea exhibits considerable morphological variability throughout its distribution and taxon has been split into various subspecies and varieties. Godt and Hamrick have recently made an allozyme survey of infra - specific subdivisions and conclude, as does McDaniel, that only two subspecies are well supported by combined molecular and morphological data: southern pubescent taxon, S. Purpurea subsp. Venosa wherry and northern glabrous taxon, S. Purpurea subsp. Purpurea. Sarracenia purpurea is a long - living perennial producing a strong rhizome that allows species to spread horizontally. Even though its life cycle has not been studied precisely, Schwaegerle and Schaal report from eight to 15 generations in 70 years. Demographic investigation of Swiss populations led to an approximation of lifetime of 20 years for individual and shows that reproduction first happens after only 3 years, while maximum flowering occurs after 10 years. The flower is protandrous and presents unusual sophisticated morphology: pistil has umbrella shape with stigma at angles, tightly enclose by bracts, petaloid sepals and petals. This specialized system is thought to be adaptation promoting allogamy by secondary pollen presentation. Although Thomas and Duncan report from field experiments that species seem mostly outcrossing, morphological specialization of flowers can only be viewed as leaky mechanism to prevent autogamy; at least, selfing by geitonogamy is unavoidable. Nevertheless, self - compatibility in S. Purpurea does not seem to have been investigated so far. Flowering is synchronous among individuals of the same population. Seeds measure about 2 mm and present vestigial lateral wings. Seed dispersal is thus not very efficient and long - distance dispersal can only be achieved by hydrochory. Because of its carnivorous biology and showy morphology, S. Purpurea has often been transplanted into previously unoccupied stations. Such introductions, when document, are promising opportunities to study micro - evolutionary processes. This is precisely the reason why S. Purpurea was one of the first plant species to be studied empirically in the framework of evolutionary consequences of bottleneck. In that study, American population, artificially found by a single individual 75 years ago, was shown by allozyme survey to harbour 25 times less genetic diversity. Taggart et al. Also, study this species in this framework after it was introduced outside of its native range into Ireland. Using the same loci as Schwaegerle and Schaal, they study population first introduced in 1906, as well as populations found from this stock.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Sources

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

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