Origins of Life on Earth

• What is the RNA World Hypothesis?

  RNA was the earliest form of genetic material
• Why did DNA replace RNA as genetic material?

  DNA is more stable and less mutation-prone
• What did the Miller/Urey experiment demonstrate?

  Organic molecules can form from inorganic substances
• What inorganic substances were used in the Miller/Urey experiment?

  H2O vapor, H2, NH3, CH4
• What do some scientists believe about the origin of organic molecules?

  They were brought by meteorites or celestial events
• How many mass extinctions have occurred in Earth's history?

  At least 5
• What happened during the Ordovician-Silurian extinction?

  Many small marine organisms died out
• When did the Devonian extinction occur?

  Approximately 365 million years ago
• What percentage of marine species went extinct during the Permian-Triassic extinction?

  95%
• What is the most famous mass extinction event?

  The Cretaceous-Tertiary extinction
• What can cause rapid extinction rates?

  Sudden ecological stresses
• What is one cause of ecological stress leading to extinction?

  Sudden volcanic activity
• How does changing climate contribute to extinction?

  It alters habitats and species survival
• What is an anoxic event?

  Oxygen deficiency in ocean layers
• What determines biodiversity in an ecosystem?

  Rates of speciation and extinction
• What happens after mass extinction events?

  Periods of rapid evolution/speciation occur
• What is punctuated equilibrium?

  Rapid evolution following mass extinctions
• How does genetic diversity affect a population's resilience?

  Higher diversity increases adaptability to changes
• What happened to the Irish potato variety "lumper" in the 1800s?

  It was decimated by a rot
• What is the consequence of low genetic diversity in populations?

  Increased risk of decline/extinction
• How do mutations contribute to bacterial evolution?

  They provide raw material for evolution
• How does antibiotic resistance evolve in bacteria?

  Through natural selection of resistant mutations
• What happened to the cheetah population about 12,000 years ago?

  It experienced a near-total extinction
• What is a consequence of the cheetah population bottleneck?

  Reduced genetic diversity and health issues