Fossils & Extinction

• What are fossils?

  Remains of long-dead organisms
• Why is studying fossils important?

  They provide information about extinct organisms
• How do fossils provide evidence for evolution?

  They show incremental changes over time
• What are the three main ways fossils can form?

  1. Gradual replacement by minerals
  2. Casts and impressions
  3. Preservation without decay
• How do gradual replacement fossils form?

  Body parts decay and are replaced by minerals
• What are casts in fossil formation?

  Impressions left by decayed organisms in clay
• What are impressions in fossils?

  Marks left by organisms like footprints
• How can fossils form through preservation?

  Organisms get trapped in amber or tar
• What conditions prevent decay in preservation fossils?

  No oxygen or moisture present
• When is a species considered extinct?

  When no individuals of that species remain
• What is a common reason for species extinction?

  Rapid environmental changes
• How can new predators contribute to extinction?

  They can kill off existing species
• How has human hunting affected species extinction?

  It has driven entire species to extinction
• How can diseases lead to extinction?

  They can spread and kill populations