Genetics and evolution

• fossils


  remains of organisms from millions of years ago found in rocks
• how fossils are formed

  • parts of organisms haven’t decayed - temp is too cold, not enough oxygen or water
  • parts of organism are replaced by minerals as they decay
  • preserved traces of organisms e.g. footprints
• not sure how life on Earth began

  • earliest forms of life were soft-bodied organisms
  • many fossil traces destroyed by geological activity
• extinction


  the permanent loss of all members of a species
• how extinction is caused

  • catastrophic event
  • changes in environment e.g. temperature, weather patterns
  • new predators
  • new disease
• evidence of evolution

  • fossils
  • resistant bacteria
• antibiotic-resistant bacteria

  • mutation makes strains of bacteria resistant to antibiotics
  • survives and reproduces, population rises
• why does resistant strain spread?

  • people aren’t immune to it
  • no effective treatment
• what bacteria is resistant to antibiotics?

  MRSA
• reduce development of antibiotic resistant bacteria

  • doctors don’t prescribe antibiotics inappropriately/overuse them
  • patients complete full course of antibiotics - all bacteria killed, none survive to form strains
  • restrict use of antibiotics in farming
• classification


  organisation of living things into groups according to their similarities
• Carl Linnaeus

  • grouped organisms together based on structure and characteristics
• types of kingdoms

  • animal kingdom
  • plant kingdom
• Linnaean/natural classification system


  • kingdom
  • phylum
  • class
  • order
  • family
  • genus
  • species
• binomial system


  organism is named from genus and species
• kingdom


  • contains lots of organisms with many differences
• species


  • group of organisms that breed together and produce fertile offspring
• • development of microscopes - look at internal structures
  • analyse and understanding biochemistry e.g. DNA
• who developed the three domain system?

  Carl Woese compared biochemistry of ribosomes and how cells reproduce
• domain


  • higher level of classification above kingdom
• three domain system

  • archea
  • bacteria
  • eukaryota
• archea


  • primitive bacteria e.g. extremophiles (live in extreme conditions)
  • kingdom - archaebacteria
• bacteria


  • true bacteria and cyanobacteria (bacteria-like organisms that photosynthesise)
  • kingdom - eubacteria
• eukaryota


  • cells have genetic info enclosed in DNA
  • kingdoms - animals, plants, fungi, protists
• evolutionary trees


  • show how closely related organisms are
  • use classification data and fossil data