Earth's Life Support Systems

Climate - temperature on earth does not go from one extreme to another (Mercury can go from -200 to 375)

Light - all planets receive light from sun but earth uses it most; plants need sun to grow in photosynthesis, this releases oxygen; earth takes 24 hours to spin on its axis

Atmosphere - earth has a breathable atmosphere; plenty of oxygen (21% of air); a small amount of CO2 (0.04) poisonous gas, makes up most of Venus and Mars; atmosphere is kept on earth by gravity

Water - most important chemical necessary for life; water doesn't burn skin like acids do; it's drinkable

Sun - earth receives perfect amount of heat and light to support life; sun's gravity keeps earth in its orbit, earth would float away if sun vanished

• it's 'just the right' distance from the sun to allow the presence of LIQUID water on the surface of the planet
• 500 million - 150 billion planets exist in goldilocks zone
  • Planet HD 40307g - 7x larger than earth
  • Tau Ceti E - older sun 1/2 amount of life
  • Gileses 581d - more pull of gravity than earth

People

• cooling us - sweating, evaporation of water off surface of skin
• required for chemical reactions - including circulation of oxygen and nutrients
• economic activity - generates electricity, irrigate crops, recreational facilities, drinking, sewage (public demands), food manufacturing, brewing, paper and steel making

Flora

• photosynthesis - occurs in leaves, combines CO2, sunlight and water to produce glucose and starch
• respiration - converts glucose into energy through its reaction with water, also releases water and CO2
• transpiration - transpiration of water from leaf surfaces cools plants by evaporation
• plants need water to maintain rigidity and transport minerals

Fauna

• respiration - converts glucose into energy through its reaction with water, also releases water and CO2
• required for chemical reactions - including circulation of oxygen and nutrients
• cooling by evaporation - panting is done by fur-covered animals, birds and reptiles

Climate

• create benign thermal conditions on earth
• oceans (71% earth) moderate temperature - absorb heat, store heat, release heat slowly
• clouds reflect 1/5 of incoming solar radiation - lower surface temperatures
• water vapour (greenhouse gas) absorbs long wave radiation from earth - makes earth 15 degrees C hotter otherwise

Atmosphere - the envelope of gases surrounding the planet

Biosphere - the space at the earth's surface and within the atmosphere occupied by living organisms

Lithosphere - the rigid outer part of Earth, consists of the crust and upper mantle. It's divided into tectonic plates

Cryosphere - the frozen part of Earth's surface, including polar ice caps, continental ice sheets, glaciers, sea ice and permafrost

Hydrosphere - all the waters on the Earth's surface, such as lakes and seas

System - a set of components that work together. There are inputs, transfers (flows), stores and outputs

Closed system - input, output, and transfer of energy but not matter or mass (EG: the hydrological cycle)

Open system - inputs and outputs of both energy and matter EG: the drainage basin system)

The Global Hydrological Cycle

• energy from sun enters and leaves the system
• the total amount of water in cycle is always the same
• no water enters or exits
• closed system

The Drainage Basin Hydrological System

• a drainage basin is an area of land drained by a river
• energy comes into and leaves the drainage basin
• mass (water, sediment) can also enter and leave
• open system