Variation

• Organisms of the same species have differences
• Differences between organisms of the same species

  • Different colour hair
  • Individually shaped noses
  • Variety of heights
• Variation within a species

  Genetic variation and environmental variation
• Genetic variation


  • Characteristics are determined by the genes inherited from parents
  • Genes are passed on in sex cells (gametes)
  • Most animals and plants get some genes from the mother and some from the father
  • Combining of genes from two parents causes genetic variation
• Characteristics determined only by genes


  • Violet flower colour
  • Eye colour
  • Blood group
  • Inherited disorders (e.g. haemophilia or cystic fibrosis)
• Environmental variation


  Differences caused by the conditions that organisms live and grow in
• Environmental variation


  • Plant grown in plenty of sunlight vs plant grown in darkness
• Most characteristics are determined by a mixture of genetic and environmental factors
• Maximum height


  Determined by genes, but actual height depends on environment (e.g. how much food)
• Mutations


  Changes to the sequence of bases in DNA
• Most mutations have no effect on the protein the gene codes for, so most mutations have no effect on the organism's phenotype
• Although it's very rare, mutations can result in a new phenotype (characteristic) being seen in a species
• If the environment changes, and the new phenotype makes an individual more suited to the new environment


  It can become common throughout the species relatively quickly by natural selection