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Population bottleneck followed by recovery or extinction. A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as genocide, speciocide, widespread violence or intentional culling.
Genetic pollution is a term for uncontrolled [1] [2] gene flow into wild populations. It is defined as "the dispersal of contaminated altered genes from genetically engineered organisms to natural organisms, esp. by cross-pollination", [3] but has come to be used in some broader ways.
A neutral mutation is one that does not affect an organism's ability to survive and reproduce. The neutral theory allows for the possibility that most mutations are deleterious, but holds that because these are rapidly purged by natural selection, they do not make significant contributions to variation within and between species at the ...
The golden toad of Monteverde, Costa Rica, was among the first casualties of amphibian declines.Formerly abundant, it was last seen in 1989. Since the 1980s, decreases in amphibian populations, including population decline and localized mass extinctions, have been observed in locations all over the world.
In more detail, the accumulation of mutations in small populations can be divided into three phases. In the second phase a population starts in mutation/selection equilibrium, mutations are fixed at a constant rate through time, and the population size is constant because the fecundity exceeds mortality.
The classical theories of evolution (mutation accumulation, antagonistic pleiotropy, and disposable soma) [1] [2] [3] suggest that environmental factors, such as predation, accidents, disease, and/or starvation, ensure that most organisms living in natural settings will not live until old age, and so there will be very little pressure to ...
The CDC said the patient's sample showed mutations in the hemagglutinin (HA) gene, the part of the virus that plays a key role in it attaching to host cells. The mutations seen in the patient are ...
The mutations on which the process depends are random events, and, except for the "silent mutations" which do not affect the functionality or appearance of the carrier, are thus usually disadvantageous, and their chance of proving to be useful in the future is vanishingly small.