Variation

• Variation is

  Differences between organisms of the same species
• Continuous variation

  Gradual change in a population with no distinct categories

  Height

  Handspan

  Mass

  Histogram
• Discontinuous variation


  People are clearly divided into a group with no intermediates

  Blood group

  Eye colour

  Tongue rolling

  Bar chart
• Genetic factors of variation

  Passed down from parents by the chromosomes in the nucleus of the eggs or sperm
• Every human cell has

  46 chromosomes
• Genes are

  short lengths of DNA that code for a particular characteristic(protein)
• Environmental factors in variation

  our surroundings may cause variation
• Human environmental factors

  Sunlight darkens skin and lightens hair

  Diet affects body mass
• Plant environmental factors

  Temperature affects how fast plants grow
• Dna is

  deoxyribonucleic acid
• DNA shape

  Double helix
• DNA structure


  The sides are sugar and phosphate molecules

  The ’rungs’ are made from bases- chemical molecules made from nitrogen
• The 4 DNA bases

  Adenine

  Thymine

  Cytosine

  Guanine
• Purpose of variation

  Reduces the chances of extinction
• Natural selection


  Variation exists in a species

  There is competition for resources

  Organisms with best features survive- survival of the fittest

  The “fittest” breed and pass down their genes
• Features that help to survive better are

  adaptations
• The change in a species over a long time due to adaptations

  Evolution