• Living organisms need chemical reactions to live, grow, and reproduce.
  • The chemical reactions occur in sequences of steps known as metabolic pathways.
  • The metabolic pathways are very similar for all life on Earth.
  • This means that the metabolic pathways evolved very early in Earth's history.
  • Some scientists think that RNA was the first replicating molecule.
  • Every organism has a collection of genes that code for the traits that organism could have.
  • Not all genes are expressed; therefore, knowing all of your genes does not tell you exactly who you are.
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