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B5 (Evolution (Natural selection (1) Variation caused in species, 2)…

- - - - Oldest rocks contain simplest organisms
      - Show changes that happen over time
      - Transitional fossils
    - - Selective breeding e.g. race horses
      - Not necessarily aiding survival
    - - Pentadactyl limb
      - Common ancestor that diverges
    - - Early embryos share similar structures
      - Same for all species
    - - All organisms use DNA as genetic code
      - Closer the sequence, close the common ancestor
  - - - Based on observed characteristics
      - Kingdom, Phylum, Class, Order, Family, Genus, Species
      - binomial nomenclature - Latin name of two parts
    - - Based on DNA and common ancestory
      - phylogeny - study of evolutionary links
      - Similarities in DNA studied
- - - - silent i.e. no change in amino acid
      - missense i.e. change in amino acid
      - nonsense i.e. codes for stop codon
      - e.g. sickle-cell anemia
    - - extensive missense i.e. affects all downstream
    - - Spontaneous
      - Chemicals e.g. benzene, ethanol
      - Ionising radiation