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Encyclopedia > Population bottleneck

A population bottleneck (or genetic bottleneck) is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing, and the population is reduced by 50% or more, often by several orders of magnitude. A graph of this change resembles the neck of a bottle, from wide to narrow; hence the name. Charles Darwin, father of the theory of evolution by natural selection. ... An order of magnitude is the class of scale or magnitude of any amount, where each class contains values of a fixed ratio to the class preceding it. ... Reusable glass milk bottles A bottle is a small container with a neck that is narrower than the body and a mouth. ...


Population bottlenecks increase genetic drift, as the rate of drift is inversely proportional to the population size. It also changes the relationship of natural selection (see: inbreeding). Genetic drift is a contributing factor in biological evolution, in which traits which do not affect reproductive fitness change in a population over time. ... Natural selection is a process by which biological variants within a population get to reproduce more or less relative to other variants in the same population because they happen to perform/function better or worse than the other variants. ... Inbreeding is breeding between close relatives. ...

Contents


Humans

DNA evidence suggests that humans today are a legacy of a population bottleneck which occurred 70,000 years ago. This would have had the result of limiting the overall level of genetic diversity in the human species, possibly by a large amount. The evidence that all living humans are descended from fewer than ten thousand people alive at that time comes both from mitochondrial DNA coalescence, and the relatively small variations in the human Y chromosome. Space-filling model of a section of DNA molecule Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and most viruses). ... Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu (extinct) Homo sapiens sapiens For other uses, see Human (disambiguation). ... The human Y chromosome is one of two sex chromosomes, it contains the genes that cause testis development, thus determining maleness. ...


One theory about this bottleneck is the Toba catastrophe theory, positing that the human population was reduced to a few thousand individuals when the Toba supervolcano in Indonesia erupted and triggered a massive environmental change. According to the Toba catastrophe theory, modern human evolution was affected by a recent large volcanic event. ... View of Lake Toba Lake Toba is a large lake, 100km long and 30km wide, in the middle of the northern part of the Indonesian island of Sumatra. ... A supervolcano refers to a volcano that produces the largest and most voluminous kinds of eruptions on earth. ... This article needs a complete rewrite for the reasons listed on the talk page. ...


In 2000, a Molecular Biology and Evolution paper suggested a transplanting model or a 'long bottleneck' to account for the limited genetic variation, rather than a catastrophic environmental change. (See "Population Bottlenecks and Pleistocene Human Evolution".) This article is about the year 2000. ...


Examples in the animal world

Year Estimated American
bison population size
Before 1492   60,000,000
1890   750
2000   350,000

Wisent, also called European bison, faced extinction in the early 20th century. The 3600 animals living in 2000 are all descended from 12 individuals and only two distinct Y chromosomes are left in the species. The population of American Bison fell due to overhunting, nearly leading to extinction around the year 1890 and has since begun to recover. Events January 2 - Boabdil, the last Moorish King of Granada, surrenders his city to the army of Ferdinand and Isabella after a lengthy siege. ... 1890 was a common year starting on Wednesday (see link for calendar). ... This article is about the year 2000. ... Binomial name Bison bonasus (Linnaeus, 1758) The Wisent (pronounced vE-zent) is the European bison, species Bison bonasus. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... This article is about the year 2000. ... The human Y chromosome is one of two sex chromosomes, it contains the genes that cause testis development, thus determining maleness. ... Binomial name Bison bison Linnaeus, 1758 Subspecies B. b. ...


A classic example of a population bottleneck is that of the northern elephant seals, whose population fell to about 30 in the 1890's although it now numbers in the tens of thousands. Another example are cheetahs, which are so closely related to each other, that skin grafts from one cheetah to another do not provoke immune responses, thus suggesting an extreme population bottleneck in the past. Another largely bottlenecked species is the Golden hamster, for which the vast majority are descended from a single litter found in the Syrian desert around 1930. Binomial name Mirounga angustirostris (Gill, 1866) The Northern Elephant Seal (Mirounga angustirostris) is one of two species of elephant seal (the other is the Southern Elephant Seal). ... Binomial name Acinonyx jubatus (Schreber, 1775) The Cheetah (Acinonyx jubatus) is an atypical member of the cat family (Felidae) that hunts by speed rather than by stealth or pack tactics. ... Skin Graft is a highly influential contemporary No Wave, Noise Rock, Art Punk Rock label based out of Chicago. ... The immune system is the system of specialised cells and organs that protect an organism from outside biological influences. ... Binomial name Mesocricetus auratus Waterhouse,, 1839 The Syrian Hamster or Golden Hamster, Mesocricetus auratus, is the best known member of the rodent subfamily Cricetinae, the hamsters. ... 1930 is a common year starting on Wednesday. ...


According to a paper published in 2002, the genome of the panda shows evidence of a severe bottleneck that took place about 43,000 years ago1. There is also evidence of at least one primate species that suffered from a bottleneck around this time scale. Panda can have several different meanings: The Giant Panda is a large black-and-white bear-like mammal native to China. ...


Sometimes further deductions can be inferred from an observed population bottleneck. Among the Galapagos archipelago's giant tortoises (themselves a prime example of a founder effect), the comparatively large population on the slopes of Alcedo volcano is significantly less diverse than four other tortoise populations on the same island. Researchers' DNA analysis dates the bottleneck around 88,000 years before present (YBP), according to a notice in Science, October 3, 2003. About 100,000 YBP the volcano erupted violently, burying much of the tortoise habitat deep in pumice and ash. The coincidence is suggestive. NASA Satellite photo of the Galápagos archipelago. ... The founder effect is an evolutionary phenomenon. ... October 3 is the 276th day of the year (277th in Leap years). ... 2003 (MMIII) is a common year starting on Wednesday of the Gregorian calendar. ...


See also

Species with a small population size are subject to a higher chance of extinction because their small population size makes them more vulnerable to genetic drift, resulting in stochastic variation in their gene pool, their demography and their environment. ... The effective population size (Ne) is defined as the number of breeding individuals in an idealized population that would show the same amount of dispersion of allele frequencies under random genetic drift or the same amount of inbreeding as the population under consideration (Sewall Wright). ... The founder effect is an evolutionary phenomenon. ... Overpopulation indicates a scenario in which the population of a living species exceeds the carrying capacity of its ecological niche. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... Illustration of the Black Death from the Toggenburg Bible (1411). ... The Red Ribbon is the global symbol for solidarity with HIV positive people and those living with AIDS. AIDS is an acronym for Acquired Immunodeficiency Syndrome or Acquired Immune Deficiency Syndrome and is defined as a collection of symptoms and infections resulting from the depletion of the immune system caused... According to the Toba catastrophe theory, modern human evolution was affected by a recent large volcanic event. ...

Notes

  • 1 Paper: "Genetic diversity and conservation of endangered animal species"

External links

Topics in population genetics
Key concepts: Hardy-Weinberg law | Fisher's fundamental theorem | neutral theory
Selection: natural | sexual | artificial | ecological
Genetic drift: small population size | population bottleneck | founder effect
Founders: Ronald Fisher | J.B.S. Haldane | Sewall Wright
Related topics: evolution | microevolution | evolutionary game theory | fitness landscape
List of evolutionary biology topics

  Results from FactBites:
 
Population bottleneck - Wikipedia, the free encyclopedia (489 words)
A population bottleneck (or genetic bottleneck) is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing, and the population is reduced by 50% or more, often by several orders of magnitude.
Population bottlenecks increase genetic drift, as the rate of drift is inversely proportional to the population size.
A classic example of a population bottleneck is that of the northern elephant seals, whose population fell to about 30 in the 1890's although it now numbers in the tens of thousands.
Population genetics - Wikipedia, the free encyclopedia (698 words)
Population genetics is the study of the distribution of and change in allele frequencies under the influence of the five evolutionary forces: natural selection, genetic drift, mutation, migration and nonrandom mating.
Population genetics was a vital ingredient in the modern evolutionary synthesis, its primary founders were Sewall Wright, J.
In practice, there are two bodies of evolutionary theory that exist in parallel, traditional population genetics operating in the genotype space and the biometric theory used in plant and animal breeding, operating in phenotype space.
  More results at FactBites »

 
 

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