Fossils

• Fossils

  Remains of organisms from millions of years ago which are found in rocks
• How fossils form

  1. Parts of organisms have not decayed

  2. Parts of organism are slowly replaced by minerals during decay

  3. Preserved traces of organisms (e.g. footprints, root spaces)
• Many of the earliest forms of life were soft-bodied organisms which rarely form fossils
• Many fossils that did form have been destroyed by changes to rocks in the Earth's crust
• Because there are very few fossils of the early forms of life, scientists cannot be certain how life on earth began
• Fossils show that a huge number of species have become extinct
• Extinct species

  No remaining individuals of that species still alive
• Reasons species can become extinct

  • Catastrophic event (e.g. asteroid collision)
  • Environmental changes (e.g. weather, new disease, new predator)
  • New more successful species evolves and competes for resources
• Plenty of questions on fossils and extinction in the revision workbook