AQA AS Biology Unit 2 3.2.3 Genetic Diversity

A PowerPoint presentation summarising chapter 9 from the AQA AS Biology textbook. Topic 3.2.3 from the specification. Made using my class notes, the AQA AS Biology textbook and the specification. 

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Unit 2 The Variety of Living

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Genetic Diversity
Similarities and differences between organisms are determined by
the similarities and differences in their DNA code.
Gene pool
Total amount of inherited information in a species.
Different forms of genes.
The greater the number of alleles in a species then the greater the
genetic diversity in that species.
Genetic diversity is important in a species for the long term survival
of that species, as the greater the genetic diversity, the more likely
that the species is able to adapt and to survive changes in the
Mutation increases genetic diversity as a mutation is a change in the
sequence of bases on the DNA. Mutation therefore creates new
alleles.…read more

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Factors that decrease genetic diversity
1. Selective breeding;
Involves humans artificially choosing organisms
with desirable characteristics and using them as
breeding stock.
Over many generation, a population will be
produced which has the desirable characteristics
but has a greatly reduced genetic diversity.
Long term consequences may be an inability to
adapt to any sudden environmental changes.…read more

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Factors that decrease genetic diversity continued
2. Genetic Bottlenecks;
Situation when a population recovers from a small
number of individuals.
The new population is likely to show low variation
since many alleles have been lost from the gene
Environmental catastrophes and human
intervention are the cause of genetic bottlenecks.…read more

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Factors that decrease genetic diversity continued
3. The Founder Effect;
A situation where a population is founded by just a
few individuals, who are not representative of the
gene pool from which they came.
Therefore, since there is a smaller gene pool, there
are less alleles so the population that develops will
have a low genetic diversity.…read more

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Factors that decrease genetic diversity continued
4. Random Genetic Drift (Sewall Wright Effect);
Applies to a small population with a limited
breeding population.
Due to random mating, by chance some alleles can
be completely lost from a population whilst others
become more common.…read more


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