Variation

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Variation

• Leaving Certificate Biology

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Variation in Humans

• Humans share all the same characteristics
• 2 legs, 2 arms and a head etc.

No two humans are exactly alike in terms of
appearance, behavior and intelligence.
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Acquired Variation

• You are not born with these types of variations.
• These are learned or picked up through your
  lifetime.
• These variations are the influence of the
  environment of each individual.
• Examples
• Which language do you speak?
• Which sport do you play?

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Inherited Variation - Heredity

• These are variations inherited from your parents.
• You may inherit your mothers blue eyes but not
  her blond hair.
• You may have the same shape nose as your father
  but not grow as tall as him.
• Thus you inherit different traits from each
  parent.
• See example in the next slide

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• You also bear a similarity to your siblings.
• Siblings are different in physical appearance due
  to the inheritance of different characteristics
  from each parent.
• See example in the next slide

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Inherited characteristics

• We all have the same the inherited
  characteristics.
• but
• We all have different versions of the same
  characteristics called traits.

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Genes

• Characteristics are controlled by genes.
• For example everyone has genes which determines
  hair colour.
• But not everyone has the same version of those
  genes.
• So there is more than one type of gene for hair
  colour that you could have.

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Genotype

• The genotype is the of genes you inherit from
  your parents.

The set of genes you inherit from your parents
determines the traits you will have Hair
colour? Eye Colour? Height? Skin colour?
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Phenotype

• Phenotype

Environment
Genotype
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• Identical twins who were raised apart, Roger
  (left) and Tony first met at twenty-five and
  discovered they had many similarities. Photograph
  by Nancy Segal