Evidence of Evolution

• Fossils are the ‘remains’ of organisms from millions of years ago, which are found in rocks
• Fossils may be formed:

  • From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
  • When parts of the organism are replaced by minerals as they decay
  • As preserved traces of organisms, such as footprints, burrows and rootlet traces
• Many early forms of life were soft-bodied, which means that they have left few traces behind
• Traces of life have been mainly destroyed by geological activity which means that scientists cannot be certain about how life began on Earth
• We can learn from fossils how much or how little different organisms have changed as life developed on Earth
• Extinctions occur when there are no remaining individuals of a species still alive
• Species can go extinct when there is a

  • Catastrophic event
  • New environment
  • New disease
  • New predator
  • New competitor
• Bacteria can evolve rapidly because they reproduce at a fast rate
• Resistant bacteria are bacteria that have become resistant to antibiotics

  
• MRSA is resistant to antibiotics
• To reduce the rate of development of antibiotic resistant strains:

  • Doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections
  • Patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains
  • The agricultural use of antibiotics should be restricted
• The development of new antibiotics is costly and slow so it is unlikely to keep up with the emergence of new resistant strains