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Inbreeding is also used to reveal deleterious recessive alleles, which can then be eliminated through assortative breeding or through culling. In plant breeding, inbred lines are used as stocks for the creation of hybrid lines to make use of the effects of heterosis. Inbreeding in plants also occurs naturally in the form of self-pollination.
However, inbreeding also gives opportunity for genetic purging of deleterious alleles that otherwise would continue to exist in population and could potentially increase in frequency over time. Another possible negative effect of inbreeding is weakened immune system due to less diverse immunity alleles as a result of outbreeding depression. [6]
Genetic purging is the increased pressure of natural selection against deleterious alleles prompted by inbreeding. [1]Purging occurs because deleterious alleles tend to be recessive, which means that they only express all their harmful effects when they are present in the two copies of the individual (i.e., in homozygosis).
Charles Darwin was one of the first scientists to demonstrate the effects of inbreeding depression, through numerous experiments on plants. Darwin's wife, Emma, was his first cousin, and he was concerned about the impact of inbreeding on his ten children, three of whom died at age ten or younger; three others had childless long-term marriages.
The Westermarck effect has gained some empirical support. [2] Proponents point to evidence from the Israeli kibbutz system, from the Chinese Shim-pua marriage customs, and from closely related families. In the case of the Israeli kibbutzim (collective farms), children were reared somewhat communally in peer groups, based on age, not biological ...
Although heat has a negative impact on the health of the entire population, some factors may increase the risk of adverse outcomes. [31] People who are at an increased risk of dying from heat exposure include the elderly, young children, those who have low socioeconomic status or pre-existing diseases. [31]
A systematic review of neurodevelopmental effects of prenatal and postnatal organophosphate pesticide exposure was done in 2014. The review found that "Most of the studies evaluating prenatal exposure observed a negative effect on mental development and an increase in attention problems in preschool and school children." [30]
Inbreeding – Reproduction by closely related organisms; Inbreeding avoidance – Evolutionary biology concept of prevention of negative inbreeding effects; Inbreeding depression – Reduced fitness as a result of inbreeding; Incest – Sexual activity between immediate family members or people considered too closely related to marry