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What leads to genetic diversity?

The differences in DNA



One of a number of alternative forms of a gene. Organisms differ in their alleles not their genes.


What makes species (and individuals within a species different from one another?

The combination of alleles they posses.


The greater the number of alleles that all members of a species have...

The greater the genetic diversity.


The greater the genetic diversity...

the more likely that a species will be able to adapt to some environmental change.


Why are species with a greater genetic diversity more likely to be able to adapt to environmental change?

Wider range of alleles and there and therefore a wider range of characteristics. There is therefore a greater probability that some individual will posses a characteristic that suits it to the new environmental conditions.


Genetic diversity is reduced when..

a species has FEWER alleles.


How does selective breeding (artificial selection) work?

Involves identifying individuals with desired characteristics and using them to parent the next generation. Offspring that do not exhibit the desired characters are killed, or at least prevented from breeding. In this way alleles for unwanted characteristics are bred out. of the pop. The variety in the pop. is deliberately restricted to a small number of desired alleles. Over many generations, this leads to a pop which all posses desired qualities but with reduced genetic diversity.


Why is selective breeding often carried out?

In order to produce high yielding breeds of domesticated animals and strains of plants.


What is the founder effect?

When just a few individuals from a pop. colonise a new region. These few individuals will carry with them only a small fraction of the alleles of the pop as a whole. These alleles may not be representative of the larger pop. New pop that develops from new coloniser shows less genetic diversity than the pop from which it came from. New pop. may develop into new species. These species have fewer alleles so are less able to adapt to changing conditions.


When is the founder effect often seem?

When new volcanoes rise out of the sea, The few individuals that colonise the barren islands give rise to pops that are genetically distinct from the pop they left behind. The new pop may develop into new species.


What are genetic bottlenecks?

Pops. of a species may from time to time suffer a dramatic drop in numbers. Sometimes the reason for this drop is a chance event, such as a volcanic eruption or interference by man. Few survivors will possess a much smaller variety of alleles than the original pop. LESS GENETIC DIVERSITY. As individuals breed and become more established, the genetic diversity of new pop. will remain restricted. Less diversity means fewer alleles, making it less likely that the pop can adapt to any change in its environment.