Conditions for life on earth
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How is an atmosphere retained on earth?
By the mass of the earth and gravity
How is liquid water maintained on earth and why is this important?
Atmospheric pressure stops water from boiling. Water is important as it is the physiological solvent in which most biological reactions take place.
What does the atmosphere provide?
Gaseous resources, CO2, CH4, NH2
What does the distance from the sun allow on earth
A suitable amount of insolation which produced suitable temps for earth.
What is incoming insolation controlled by?
Surface albedo, infrared absorption and the atmosphere
What is the axis of rotation of earth and what does it produce?
The axis of rotation is at an angle to its orbit around the sun, it produces seasonal variations.
What does the speed of rotation of earth allow?
The 24hr period of rotation stops temperature extremes
How is the magnetic field/magnetosphere produced and what does it do?
Produced by the earths molten core. The magnetic field deflects solar wind and prevents damaging radiation from reaching the earth.
When did life first develop on earth?
3.5 billion years ago
How did liquid water allow life to develop?
As a solvent for chemical reactions. Transport of dissolved gases, nutrients etc in blood and sap. Temperature control, High SHC Aquatic habitats Absorbed UV radiation before the ozone developed which protected aquatic organisms
How was oxygen first produced?
Photosynthetic bacteria in the oceans developed the ability to photosynthesise and release oxygen.
How did oxygen get into the atmosphere?
All the oxygen being produced by photosynthetic bacteria reacted with iron in the oceans. Once all the iron had reacted, surplus oxygen built up and diffused into the atmosphere
What did oxygen in the atmosphere do?
Oxygen absorbed UV light in the stratosphere producing O, O2 and O3. O3 is ozone and so the build up of this allowed life to develop on earth as less UV radiation was reaching earth.
What happened after the ozone developed?
Anaerobic organisms died out or they developed a way to aerobically respire and lived on land. Includes photoautotrophs and animals
What did the photoautotrophs do once developed on land?
They absorbed CO2, this reduced the levels of CO2 in the atmosphere and therefore a temperature rise
What is CO2?
Carbon dioxide, it is a GH gas so it helps retain heat in the atmosphere
What did the colonisation of plants allow?
Transpiration where water vapour was returned to the atmosphere and increased rainfall allowing more plants to grow.
What did a greater variety of organisms evolving allow?
Allowed inter-connected systems and biogeochemical processes to develop.
What do biogeochemical cycles do?
They prevent the build up of wastes and stop shortages of resources.
What are the limitations of early methods of measuring climate?
Lack of historical data Proxy data not being reliable as it can be subjective Lack of scientific equipment Lack of data collection in certain areas Proxy data- pollen grains, dendrochronology,
What are some improved methods to measure climate change?
Using scientific equipment/electronic monitoring equipment Gas analysis of ice cores Satellites Remote monitoring equipment for areas not accessible
How can ice cores be analysed for past climate conditions?
Analysing the air bubbles in ice cores to detect the isotopes of oxygen and composition of atmosphere. More O18 compared to O16 indicates the temperature was lower. Analyse for methane, CO2. If the ice layers are thick it indicates a colder temperature as more snow fall.
What satellites take data on the environment?
CLOUDSAT- measures clouds to measure precipitation, uses a radar and takes photos. CALIPSO- Uses laser light from a lidar, it takes global measurements of atmospheric particles to monitor the climate
How do we know if there is significant change in climate?
Rapid or unusual change