History of life

• What was the first kind of plant on Earth?

  Wet algae
• How long ago did land-based plants with veins evolve?

  Around 450 million years ago
• When did invertebrate animals arise?

  Around 600 million years ago
• What significant event occurred about 525 million years ago?

  A sudden increase in animal life
• What is the Cambrian explosion?

  Development of vertebrates during a rapid increase in animal life
• What do palaeontologists use to create the geological timescale?

  Dating fossils and surrounding rock strata
• What does the geological timescale show?

  How species have emerged over time
• How long ago did the Earth form?

  Nearly four billion years ago
• What are the main subdivisions of the geological timescale?

  • Eras
  • Periods
• What are the three main eras in order from oldest to most recent?

  Precambrian, Paleozoic, Mesozoic
• In which period did the first fish appear?

  Silurian period
• In which period did the first reptiles appear?

  Carboniferous period
• In which period did many organisms first go extinct?

  Permian period
• In which era did mammals and birds appear?

  Mesozoic era
• When did dinosaurs become extinct?

  About 65 million years ago
• In which era and period did humans evolve?

  Cenozoic era, Quaternary period
• Why do different life forms appear and disappear at different times?

  Due to the process of evolution and changing conditions
• What is inductive reasoning?

  Using specific examples to form general ideas
• What are the two main kinds of changes affecting evolution?

  • Changes in climate
  • Geological events
• What did scientists generalize about the atmosphere of primitive Earth?

  It was mainly hydrogen, methane, ammonia, and nitrogen
• What did ultraviolet light and lightning do to primitive gases?

  Changed them into organic molecules
• What hypothesis did S.L. Miller test in 1952?

  The Oparin-Haldane hypothesis
• What is deductive reasoning?

  Using general principles to make specific predictions
• How long did the Cambrian period last?

  About 543 million years
• What happened during the Cambrian explosion?

  A large number of new animal groups appeared
• What are the main animal groups classified from the Cambrian period?

  • Platyhelminthes (flatworms)
  • Annelida (segmented worms)
  • Mollusca (snails, squids, clams)
  • Arthropoda (insects, crustaceans)
  • Echinodermata (starfish, sea urchins)
  • Chordata (vertebrates)
• What is a mass extinction?

  A period of significant species loss
• How many major mass extinctions have occurred?

  Five major mass extinctions
• When did the first mass extinction occur?

  At the end of the Ordovician period
• When did the second mass extinction occur?

  At the end of the Devonian period
• When did the third mass extinction occur?

  At the end of the Permian period
• When did the fourth mass extinction occur?

  At the end of the Triassic period
• When did the fifth mass extinction occur?

  At the end of the Cretaceous period
• What are the two types of theories on the causes of mass extinctions?

  • Environmental disasters
  • Gradual habitat changes
• What is one cause of mass extinctions related to environmental disasters?

  Meteor or asteroid impacts
• What is one cause of mass extinctions related to gradual changes?

  Changing temperatures of ice and warm ages
• What happens during an Ice Age?

  Large glaciers cover parts of the Earth
• What is continental drift?

  Movement of continental plates over time
• What was Pangaea?

  A supercontinent that existed 225-200 million years ago
• What evidence supports continental drift?

  Identical geological structures and fossils on different continents