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• Earth has existed for 4.543 billion years
• During its early formation, life is not possible because the environment does not permit it
• As time goes by, microorganisms formed into more complex organisms
• Life on earth is possible due to the following factors:
• Temperature

  • Influences how quickly atoms, molecules, or organisms move
  • Low temperature: slows down chemical reactions, produces ice
  • High temperature: break down of important biological molecules
  • Radiogenic heat: heat emitted by the planet
• Goldilocks' zone


  Earth's location where the temperature is just right
• Earth is the only planet with liquid water because some planets may have water but due to the low temperature it's only in solid form
• Water

  • Most important ingredient in biological processes
  • Absence of water will interfere with reactions necessary for life
  • Solid form (ice) hinders living organisms to use it
  • Solid (ice) in the 2 poles and liquid along the equator. (can be consumed.)
• The Ozone (03) layer shields the Earth's surface from harmful UV radiation
• Atmosphere


  • Size and distance from the sun affects the ability of the Earth to hold a significant amount of atmosphere
  • Earth's size and distance from the sun is just right which permits it to have the right amount of atmosphere
  • Presence of gravity also sustains the atmosphere
• Energy

  • Earth has rich sunlight to support life
  • Living organisms like plants and photosynthetic bacteria use light as a source of energy
  • Chemosynthetic organisms rely on chemical energy to support biological processes
  • Earth's position from the sun is just right to enable it to harness enough amount of sunlight
• Nutrients

  • Essential factor used to build and maintain organism's body structure
  • Insufficient amount can impede synthesis of biological molecules
  • Volcanism helps in cycling nutrients
  • Water, carbon, and oxygen are some examples of nutrients
• 4 Sub Systems of the Earth

  • Atmosphere
  • Geosphere
  • Hydrosphere
  • Biosphere
• Atmosphere

  Provides chemicals needed for life: carbon dioxide, nitrogen

  Provides insulation/shielding from the sun and impact of small to medium size meteorites

  Greenhouse gases like carbon dioxide (CO2) and methane (CH4) traps heat and avoid our planet from freezing
• The atmosphere extends outward about 10,000 km from the surface of the Earth
• Composition of the atmosphere

  • 78.1% nitrogen
  • 20.9% oxygen
  • 0.9% argon
  • 350 ppm carbon dioxide
  • Other components
• Layers of the atmosphere

  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Exosphere
• Geosphere

  Includes all the soil, rocks, and minerals present in the crust to the core of the Earth
• Layers of the geosphere

  • Crust
  • Mantle
  • Outer Core
  • Inner Core
• Hydrosphere

  - Composed of all the water on Earth in any form: water vapor, liquid water, and ice

  - Comprised of 97.5% saltwater and 2.5% freshwater

  - Includes all bodies of water such as oceans, lakes, rivers, and marshes

  - Clouds and rain are also part of the hydrosphere
• Water on Earth is constantly moving through the oceans in currents, with warm waters in the tropics moving toward the poles and cold water from the polar regions moving toward the tropics
• Biosphere


  - Comprised of all living things

  - Organisms interact with the other spheres to survive
• Troposphere


  Extends to about 14.5 km above the Earth's surface. It is the lowest layer where the weather forms
• Stratosphere


  Found 14.5 to 50 km above the Earth's surface. The ozone layer that protects the Earth from the Sun's harmful UV radiation is found in this layer
• Mesosphere


  Extends from 50 to 85 km above the Earth's surface. It protects the Earth from the impact of space debris
• Thermosphere


  Is found 85 to 600 km above the Earth's surface. It has charged particles that are affected by the Earth's magnetic field. The particles create the Auroras or Northern and Southern lights
• Exosphere


  Is the farthest layer. It extends to about 10 000 km above the Earth's surface
• Geosphere


  Geo-Greek for ground. Includes all the soil, rocks, and minerals present in the crust to the core of the Earth
• Layers of the Geosphere

  • Mantle
  • Inner Core
  • Outer Core
  • Crust
• Crust


  Is the outermost layer of the geosphere. It is made mostly of silicate materials
• Types of crust

  • Oceanic crust
  • Continental crust
• Oceanic crust

  Lies beneath the oceanic floors, is about 5 to 10 km thick
• Continental crust

  Makes up the continents, is about 15 to 70 km thick
• Mantle


  Made mostly of silicate rocks rich in magnesium and iron. It is about 2900 km thick. It has increasing temperatures at increasing depths
• Core


  Has a radius of 3400 km, the innermost layer of the Earth. Made out of iron and nickel. Source of internal heat because it contains radioactive materials that release energy as they decay into more stable substances
• Hydrosphere


  Hydro - Greek root for water. Composed of all the water on Earth in any form: water vapor, liquid water, and ice. Comprised of 97.5% saltwater and 2.5% freshwater. Includes all bodies of water such as oceans, lakes, rivers, and marshes. Clouds and rain are also part of the hydrosphere
• Biosphere

  Bio-Greek root that means life. The biosphere is comprised of all living things. Organisms interact with the other spheres to survive
• Factor that are necessary for life on Earth:

  • Temperature
  • Atmosphere
  • Water
  • Nutrients
  • Energy