fossils and evolution

• fossils are useful as they show how things have changed over time
• extinction means no organisms of that species survive
• 3 ways fossils are formed;

  • gradual replacement by minerals
  • casts and impressions
  • preservation (no oxygen so can't decay)
• there are no fossils of early life forms as they were soft bodied (so decayed quickly) or were destroyed by geothermal activity
• reasons for extinction

  • environment changes too quickly
  • new predator or disease
  • habitat destroyed
  • new species outcompetes