Conditions for Life on Earth
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Timeline: 4+ billion years ago
Earth formed in habitable zone of the solar system Iron + nickel core spins and creates magnetosphere Early atmosphere forms - high in greenhouse gases
Timeline: 3+ billion years ago
Water vapour condenses Microscopic life
Timeline: 2+ billion years ago
Cyanobacteria in Ocean Increase in oxygen levels causes mass extinction
Timeline: 1.2 billion - 200 million years ago
multicellular organisms plants/land animals/insects
Timeline: Today
21% oxygen complex and diverse life
4 Key conditions that allowed early life to develop
Atmosphere Magnetosphere Distance from Sun Insolation Orbital Behaviours
How has the position in the solar system allowed for development of life on Earth?
Controls temperature Correct distance from Sun for liquid water Temperature is perfect for photosynthesis
How do living organisms affect the cycling of water?
Transpiration - roots uptake water from soil and release it via water vapour Interception - trees prevent water from reaching the ground Animals drink the water Infiltration - water soaks through soil Used in photosynthesis
What other ways have living things changed conditions on Earth?
The carbon cycle (combustion of fossil fuels) The nitrogen cycle Photosynthesis (added oxygen to atmosphere) Respiration Carbon sequestrian - natural carbon capture
Outline the importance of cyanobacteria and later photosynthetic organisms
Excreted so much oxygen it created a surplus Broke down CO2 Stromatolites - rock like structures covered in cyanobacteria - contribute massively to the Earth’s supply of oxygen Some organisms adapted to the oxygen and used it to create proteins to become multicellular
How have CO2 levels changed?
decrease - 0.04%
What has caused the decrease in CO2 levels?
Photosynthesis
Where is most carbon now found?
In living things - carbohydrates In soil - decomposition
What is the magnetosphere?
The region around a planet within the planet’s magnetic field
How does the magnetosphere work?
Molten iron and nickel outer core spins - generating a magnetic field around earth
What does the magnetosphere protect the earth from?
Solar winds - blow atmosphere away Cosmic radiation - cause cancer
Why is water important for the development of life?
Universal solvent Transporter of nutrients Used in photosynthesis Provides habitats Anomalous expansion - expands when frozen High specific heat capacity - absorbs large amounts of energy with minor temp change and releases with minor temp change - moderates temperature
Why was the composition of the early atmosphere so important for the development of life?
Mostly greenhouse gases Enhanced greenhouse effect helped warm the earth
How does the Earth’s rotation around the Sun allow for the development of life on earth?
controls year length controls frequency of the seasons
How does the Earth’s tilt on its axis allow for the development of life on earth?
controls seasons hibernation migration dictates life cycles
How does the Earth’s rotation on its axis allow for the development of life on earth?
24 hour cycle controls day length controls temperature (night and day) creates only small gaps in photosynthesis