Evolution

• Evolution


  A change in the inherited characteristics of a population over time through the process of natural selection, which may result in the formation of a new species
• The Theory of Evolution states that all species have evolved from simple life forms that first developed more than 3 billion years ago
• Evolution occurs


  Because of natural selection - if a mutation provides a survival advantage, the organism is more likely to survive to breeding age and pass on the mutation to offspring
• Over many generations, the frequency of the mutation within the population will increase, and this may cause the population of a species to become so different that they can no longer interbreed to produce fertile offspring, resulting in speciation
• Evidence for evolution


  Seen in fossils, antibiotic resistance in bacteria
• Fossils


  The remains of organisms from many years ago found in rocks, formed from parts of organisms that have not decayed or been replaced by minerals
• Fossils can be used to show how the anatomy of organisms has changed over time and to compare how closely related organisms are
• Fossils cannot be used to tell us how life started on Earth because most early life forms were soft-bodied and have left few fossils, and any traces may have been destroyed by geological activity
• Extinction


  When a species has died out, which can be caused by changes in the environment, new predators, loss of food source, competition, disease, or catastrophic events
• Antibiotic resistant bacteria


  Bacteria that are not killed by antibiotics which previously cured them, due to mutations that provide resistance
• How antibiotic resistance develops

  Bacteria reproduce rapidly

  2. Mutations during reproduction can result in antibiotic resistant genes

  3. Exposure to antibiotics creates a selection pressure, so bacteria with resistance genes survive and pass on the advantageous genes
• Antibiotic resistant bacteria can spread rapidly as people are no longer immune to the treatment
• How to slow down development of antibiotic resistance

  • Antibiotics should not be given for viral infections

  2. Specific antibiotics should be given for specific bacteria

  3. Patients should complete their full course of antibiotics

  4. Antibiotics should be used less in agriculture
• How to slow transmission of antibiotic resistant bacteria

  • Maintain high standards of hygiene in hospitals

  2. Medical staff and visitors should wash hands regularly

  3. Medical staff should wear disposable or regularly sterilised clothing
• It is difficult to keep up with the development of new antibiotic resistant strains as the development of new antibiotics is expensive and slow