Evolution

• Fossil

  • A fossil is the preserved remains of a dead organism from millions of years ago.
  • They are found in rocks.
• How are fossils formed?

  • Hard body parts such as bones, which do not decay easily.
  • Conditions needed for decay are absent.
  • Preserved traces of organisms become covered by layers of sediment which eventually become rock.
• Why can't scientists be certain about how life began?

  • Many early forms of life were soft-bodied, which means that they have left few traces behind.
  • Traces that were left behind may have been destroyed by geological activity.
• What can we learn from fossils?

  • How much or how little different organisms have changed as life developed on earth
• Causes of extinction

  • Changes in the environment, geological activity.
  • New predators
  • New diseases
  • A single catastrophic event e.g volcano eruptions
• Extinction

  • Animals that have not adapted well to their environment are less likely to survive and reproduce than those that are well adapted.
  • The animals that may have not adapted to their environment may become extinct.
• Resistant bacteria

  • Mutations of bacteria produce new strains.
  • Some bacteria might become resistant to certain antibiotics, such as penicillin and cannot be destroyed by the antibiotic.
  • Evolution of bacteria is an example of natural selection.
• Development of resistance

  1. Random mutations occur in the genes of a bacteria cell.
  2. Some mutations protect the bacterial cell from the effects of the antibiotic.
  3. Bacteria without the mutation die or cannot reproduce when the antibiotic is present.
  4. Resistant bacteria can reproduce with less competition from normal bacteria strains.
• MRSA

  • Is methicillin-resistant staphylococcus aureus and it is very dangerous as it is resistant to most antibiotics.
• How to reduce the rate of development of antibiotic resistance?

  • Doctors should not prescribe antibiotics inappropriately.
  • Patients should always complete the full course of antibiotics to ensure all bacteria are killed and none do not survive and mutate.
  • The agricultural use of antibiotics should be restricted.
• Development of antibiotics

  • Costly and very slow to develop.
  • It is unlikely to keep up with the emergence of new resistant strains.
• Principles of classification

  • Developed by Carl Linnaeus
  • Linneaus classified things into:
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Three-domain system

  • Developed by Carl Woese
  • Organisms are divided into:
  • Archaea (bacteria living in extreme environments)
  • Bacteria
  • Eukaryota (includes protists, fungi, plants and animals)