Genetic Diversity

Some notes on Selective Breeding, Genetic Bottlenecks and the Founder Effect.

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Biology ­ Genetic Diversity AS
From time to time a species may suffer a big reduction in the population. This could be
as a result of an event, such as a volcanic eruption, that caused a large number of the
population die before they could reproduce. The few survivors will possess a much smaller
variety of alleles than the original population. The survivors reproduce and a larger
population is created from a few individuals. This reduces the number of different alleles
in the gene pool and so reduces genetic diversity. Less diversity means fewer alleles,
making it less likely that the population will be able to adapt to any changes in its
Describes what occurs when just a few organisms from a population start a new colony.
This could be as a result of a river diverting its course. Only a small number of
organisms contribute their alleles to the new gene pool, so genetic diversity is reduced.
As the new colony reproduce they will become genetically distinct from the population
they left behind.
Is a process that involves identifying certain individuals that possess desired
characteristics and selecting them to be the parents of the next generation. From the
resulting offspring, individuals that do not present the desired characteristics are killed
or prevented from reproducing. This means that the alleles for unwanted characteristics
are bred out of the population. The variety of alleles in the population is deliberately
reduced to a small number of desired alleles. Over many generations, this leads to an
entire population that possesses the desired characteristics but genetic diversity is

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Biology ­ Genetic Diversity AS
greatly reduced. Selective breeding is usually used in farming to produce high-yielding
strains of plants and breeds of domesticated animals.…read more


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