What are Fossils?

• What are fossils?

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

  They provide insight into 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 materials commonly decay slowly to form fossils?

  Bones, teeth, and shells
• What is a cast fossil?

  A gap left by an organism in clay
• What are impressions in fossils?

  Marks left by organisms like footprints
• How can fossils be preserved without decay?

  By being trapped in amber or tar pits
• Where can preservation without decay occur?

  In amber, tar pits, glaciers, or peat bogs
• What is the age range of the oldest fossils found?

  1. 5 to 4 billion years old
• Why is there an incomplete fossil record?

  Many early life forms were soft-bodied
• What can destroy ancient fossils?

  Volcanoes, earthquakes, and tectonic activity
• When can we say a species has gone extinct?

  When no individuals of that species remain
• What are common reasons for species extinction?

  • Rapid environmental changes
  • Arrival of new predators
  • Human hunting
  • Spread of new diseases
  • Competition from new species
  • Catastrophic events (e.g., asteroid impact)
• How can rapid environmental changes lead to extinction?

  They can destroy habitats too quickly
• How has human hunting contributed to extinction?

  It has driven entire species to extinction
• What catastrophic event wiped out the dinosaurs?

  An asteroid impact 66 million years ago
• How can diseases contribute to extinction?

  They can spread and kill populations quickly
• How can competition from new species lead to extinction?

  New species can outcompete for resources