5.3.6 evolution evidence

• Proof of evolution - antibiotic-resistant bacteria

  • bacteria reproduce rapidly
  • mutations occur during reproduction
  • if mutated bacterium is resistant to bacteria, it will survive exposure to antibiotics and will go on to reproduce
  • this bacterium will represent the original ancestor of a new resistant strain
• Proof of evolution - fossils

  • fossils show gradual changes in organisms over vast periods of time
• Apart from genes, what are the two main sources of evidence for evolution?

  Fossils

  Antibiotic-resistant bacteria
• Fossils - remaining traces of ancient life. found in rocks, preserved by natural processes
• Ways of forming fossils - hardening soft materials

  • e.g. clay hardening around an organism that is buried within it. the organism decays, leaving behind a cast of itself
• Ways of forming fossils - preservation when decay is not possible

  • where decomposers cannot act e.g. glaciers (extreme cold temperatures), peat bogs (extreme acidity)
• Ways of forming fossils - mineral replacement

  • hard parts of organisms are gradually replaced by minerals as they decay slowly, creating a rock-like substance.
  • when the surrounding sediment turns to rock, the teeth-shaped mineral structure remains distinct
• Why is the fossil record incomplete?

  • A lot of early life forms were soft-bodied. Therefore, they did not leave behind many noteworthy traces.
  • Geological activity has also caused the destruction of many traces of ancient life.
  • Because of this, scientists cannot be certain about the origins of life on Earth.
• Why can't decomposers act in peat bogs?

  Acidity
• The development of new antibiotics is a slow and costly process. it struggles to keep up with the emergence of new strains
• To reduce new resistant strains

  • doctors should avoid prescribing antibiotics when unnecessary, e.g. treating non-serious or viral infections
  • patients should finish a course of antibiotics to make sure that all the bacteria are killed
  • the use of antibiotics in agriculture (e.g. cattle feed) should be restricted
• To reduce the risks of bacterial resistance, doctors should avoid prescribing antibiotics unnecessarily, patients must finish a course of antibiotics, and the use of antibiotics in agriculture should be restricted.
• Fossils are the remains or traces of ancient life, which are found in rocks and have been preserved by natural processes.