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Variation

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Variation Revision

Variation

No two organisms are completely identical. Variation between individuals of the same species can be due to genetic factors, environmental factors or a mixture of both. 

Genetic Variation

Variation is the differences between individuals of a population, many of these differences are caused by genes, inherited from parents.

When gametes from the mother and father fuse together in fertilisation, their genetic information is combined, creating a unique set of chromosomes and causing genetic variation.

Genetic variants arise due to mutations in DNA. Mutations occur continuously but most of them have no effect on the organism’s phenotype. Occasionally, mutations will cause changes to the protein that is expressed and therefore change the phenotype of the organism. Mutations can cause rapid changes in a species if the new phenotype makes the organism more suited to an environmental change.

Characteristics in humans determined solely by genes include eye colour, blood group, inherited disorders and the ability to roll the tongue. 

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Environmental Variation

Variation between organisms can also be caused by environmental differences. Environmental variation covers everything that could cause organisms to be different that isn’t down to genetics

This means the term covers a wide range of factors, for example: 

  • People living in different areas of the world have different accents and speak different languages.
  • Accidents can cause scarring, injuries or even loss of limbs. 
  • Plants grow more healthy when they have lots of light than in the dark.
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Interacting factors

Most characteristics are due to interactions between both genetic and environmental factors.

How tall a human can potentially grow is determined by its genes, inherited from its parents. However, if they have a poor diet, they will struggle to grow to their full capacity so will be shorter.

Other examples include, body weight and skin colour.

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Variation Example Questions

Variation is the differences between individuals of a population.

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Any 2 from:

  • People in different parts of the world speak in different accents and languages.
  • Accidents can cause injuries, scarring etc.
  • Plants grow more healthy when there is more light.
  • People who eat more or do little exercise will gain more weight
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Genetics determine the maximum height the individual could grow.

Environmental factors like diet determine how well they grow.

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Variation Worksheet and Example Questions

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