The Origin of Life

Question 1

Origin of Life Theories

Answer 1

• Chemical origin (prebiotic soup)
• Panspermia: life arrived on Earth from Space
• RNA World
• Hydrothermal Vents

Question 2

What are stromatolites?

Answer 2

Bacterial communities - the earliest form of life still existing on Earth

Question 3

What do stromatolites consist of?

Answer 3

• Layers of microorganisms
• The outermost organisms are photosynthetic
• The inner layers are anaerobic supporting sulphate-reducing bacteria
• Fossil stromatolites are dated at 3.4 billion years old

Question 4

What are the Requirements of Life?

Answer 4

• Essential elements: C, H, N, O, Mg, Ca, Na, K and Fe; available on early Earth, no free O2 in atmosphere
• Temperature: between boiling and freezing points of water
• Source of energy: reduced minerals and sunlight

Question 5

Evidence of Life

Answer 5

• Stromatolites
• Isotope ratios; limestone depleted of 13CO2
• Microfossils