Paper Topic:
Natural Selection
NATURAL SELECTION : THE PROCESS , PURPOSE AND BENEFITS Natural Selection : The Process , Purpose and Benefits Why do some die and some live .The answer was clearly , that on the whole the best fitted live .This self-acting process would necessarily improve the race .the fittest would survive Alfred Russel Wallace (1823 - 1913 The term Natural selection ' which was coined by Charles Darwin explains the natural weeding-out process in which nature invariably selects the individuals that are sufficiently well adapted to the environment and allows them to survive , while it rejects those that are
br poorly adapted
Hence , the well adapted individuals reach reproductive age and hand on their favorable traits to their offspring , while less well adapted individuals fail to do so because they often perish before they reach reproductive maturity
Natural selection is not so much concerned with the survival or death of individuals as with the perpetuation of elimination of the genes carried by them , and the differential mortality as explained above helps to eliminate unfavorable alleles from the population . However , death is not the only way of achieving this , as any process that encourages the transmission of favorable alleles and blocks the transmission of unfavorable ones can be said to contribute towards evolutionary progress
Assuming an animal with unwanted attribute is somehow prevented from breeding , either by being naturally unproductive or losing in the fight for a mate , then this individual 's genes will be disallowed from going through to the next generation . And although this does not involve the death of the organism , it is just as useful at eliminating its genes from the population which can no more be said to be caused by differential mortality but by `differential fertility
I want to emphasize at this point that disadvantageous alleles are not always quickly weeded-out of a population by natural selection , because there are some cases where such allele which in a homozygous state are disadvantaged confer an advantage in the heterozygous state , hence favoring their survival
A good example is the case of Sickle cell anemia where the individual undergoes frequent `crisis ' when the mutant alleles is in the homozygous state and thus become rare , but when in heterozygous state where there is no crisis but just the sickle cell trait . Thus , these individuals are much more abundant , and this has been found out to be due to the fact that they are more resistant to Malaria
The process of natural selection as explained by the Darwin 's theory is such that since organisms often produce far more offspring than the environment can support , there always tends to be a `struggle for existence ' due to over-crowding and competition between them , and those ones with more superior physical characteristics tend to win this battle for survival
Natural selection acts on an individual 's phenotype , and this phenotype (physical characteristic ) is determined by its genetic make-up (genotype ) and the environment that the organism lives . Therefore the changes witnessed in different populations over time occur due to the changes in...
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