Conditions for Life on Earth

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					Conditions for Life
The Goldilocks Zone
 Earth’s life-sustaining
  conditions are possible
  because of its position in
  the solar system
 It is not too hot and not
  too cold – if the Earth
  was any closer or further
  away from the Sun, the
  planet could not support
  life
Other Life Sustaining Conditions
 Earth’s rotation on its axis and orbit
  around the Sun helps distribute heat
  evenly around the planet
 Earth’s magnetic field protects the planet
  from deadly radiation and particles
 Earth’s gravitational field holds the
  atmosphere in place preventing oxygen,
  nitrogen, and carbon dioxide from
  escaping into space
Four Conditions for Life
1. Stable Temperature Range
2. The Importance of Water
3. The Importance of Gases
4. The Role of the Atmosphere
Stable Temperature Range
 A stable temperature range (-50 to about +50 degrees
 Celsius) allows life to thrive – the average temperature
 has been between 10-20 degrees Celsius for 3.5 billion
 years
 The greenhouse effect allows for heat in the
 atmosphere (carbon and water vapor) to be re-radiated
 back to Earth
 Without proper water and carbon, the earth would be
 -73 degrees C.
The Greenhouse Effect
 Plants play a significant
  role in creating a stable
  temperature through
  releasing water vapor and
  oxygen by the processes of
  photosynthesis and
  transpiration

 Dark areas of vegetation
  absorb heat from the sun’s
  rays and limit the albedo
  effect – heat being
  reflected back into space
Photosynthesis
The Importance of Water
 First water likely came from volcanic activity – water collected on the
  cooling surface and as vapour in the atmosphere creating the water cycle

 Biologists believe earth first began in the oceans – blue-green algae

 Oceans cover 2/3 of the Earth – absorbs heat and distributes it around
  the world and controls our weather patterns and climates
 Helps distributes nutrients to plants
  and other organisms

 No living this consists of less than 50%
  water

 Water is the metabolizing agent that
  allows plants and animals to dissolve
  minerals and nutrients to create energy
The Importance of Gases
 78% nitrogen, 21% oxygen, carbon dioxide 0.03% -
 quite different than other planets in the solar system
 The plants have removed most of the carbon dioxide
 that originally existed and produced lots of oxygen
 Without life on earth, carbon dioxide would increase

 The production of carbohydrates, fats, and proteins
 require oxygen, carbon, and nitrogen atoms from the
 atmosphere, and hydrogen from water
The Role of the Atmosphere
 Layer of gases about 80-100 kms thick –
  very thin compared to size of Earth
 Helps maintain a consistent temperature
 Shields earth from collisions with cosmic
  particles (meteors)
 Oxygen levels at 21 allow for life, if they
  drop, animal life would not be possible, if it
  exceeds 25% most plants would be
  consumed by fire
 Oxygen is produced by plants and
  consumed by animals and the burning of
  plants and fossil fuels
The Four Spheres
1. Lithosphere – earth’s crust (soil,
  rocks, and minerals)
2. Hydrosphere – earth’s water
3. Atmosphere – the gases in the air
4. Biosphere – all living things
  (plants, bacteria, animals)
Biosphere
 Encompasses all living organisms including humans


 Divided into separate but interdependent units called
 ecosystems – well defined habitats hosting systems of
 interacting organisms

 Nutrient Cycle - Continuation of life depends on the
 constant recycling of chemical ingredients called
 nutrients (Example: plants and animals die and
 decompose)
Biosphere – The Carbon Cycle
 The movement of carbon from the
  atmosphere into plants, animals,
  and the soil and then back again

 Plants take carbon dioxide from the
  atmosphere to produce food through
  photosynthesis and release oxygen –
  animals breath oxygen and eat plants

 Dead animals and plants decay and
  return carbon to cycle

 Over production of carbon dioxide
  from factories and burning
  rainforests causes climate change
Biosphere – Nitrogen Cycle
 Most powerful element in the
 Earth’s atmosphere

 Microscopic bacteria live on
 the roots of certain plants
 known as legumes and
 converts nitrogen to ammonia
 and nitrates which the plant
 absorbs and converts to
 protein – food production
Biosphere – Oxygen Cycle
 Oxygen produced by the
 respiration of plants – 90% of
 oxygen used is replaced by
 algae in oceans

 Oxygen created by
 photosynthesis
Biosphere – Water Cycle
 Water must be recycled
  through the atmosphere and
  back to the Earth’s surface
 Most from evaporation –
  some from transpiration;
  water drawn by plants and
  released through their leaves
 Groundwater dissolves
  nutrients in the soil

				
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