Download Lesson 10: Earth`s Atmosphere

Lesson 10:
Earth’s Atmosphere
Modified From:
http://www.jhs.gjcs.k12.in.us/staff/gmauck/power_points/Chapter%2012%20History%20of%20Life%20on%20E
arth.ppt#264,2,Age%20of%20the%20Earth
http://www.physics1.howard.edu/~pmisra/ESSE%2021%20DC%20Modules%20files/06aESSE21Biosphere.ppt
#293,13,Experimental Research on the Origin of Life
http://outreach.mcb.harvard.edu/teachers/Summer06/BethMick/HistoryofLife.ppt#257,6,WHAT%20DO%20YO
U%20THINK%20EARLY%20EARTH%20WAS%20LIKE?
http://des.memphis.edu/lurbano/geog1010/Fall04/Origin_atmosphere.ppt#256,1,Origin of the atmosphere
WHAT WAS THE EARLY EARTH WAS LIKE?
• HOW OLD IS THE EARTH?
4.5 BILLION YEARS OLD
• METEORS FOR MILLIONS OF YEARS - HOW HOT
WOULD THE EARTH BE?
• Earth has to Cool Down – Steam escapes and rain allows
collection of water - Earth now has…
– atmosphere of Ammonia, Methane, Water Vapor, CO2,
and Nitrogen
– WHAT IS MISSING? Oxygen
Origin of the atmosphere
• Earth’s original atmosphere
– Probably made up of hydrogen and helium.
– These are fairly common in the universe.
• Original atmosphere stripped away by the solar
wind
– H and He are very light
• Hydrogen and helium have the smallest atoms by mass.
– The early earth was not protected by a magnetic field.
– Thus the current atmosphere is secondary
The secondary atmosphere
• Formed from degassing of
volcanoes
• Gasses emitted probably
similar to the gasses emitted by
volcanoes today.
– H2O (water), 50-60%
– CO2 (carbon dioxide), 24%
– SO2 (sulfur dioxide), 13%
–
–
–
–
–
–
–
CO (carbon monoxide),
S2 (sulfur),
Cl2 (chlorine),
N2 (nitrogen),
H2 (hydrogen),
NH3 (ammonia) and
CH4 (methane)
Earth’s Modern atmosphere
Nitrogen (N2)78%,
Oxygen (O2)21%,
Carbon Dioxide (CO2)
0.03 %,
Where did all the
oxygen come from?
In the Sea (1): Bombardment
During its early history, the Earth
was bombarded by meteorites.
Such inhospitable conditions
probably prevented life from
evolving.
NASA
Early Earth
NASA
© Julian Baum with permission
http://en.wikipedia.org/wiki/Geologic_time_scale
4500-3800 million years ago
In the Sea (2): First living things
• Life evolved
shortly after the
bombardment
ended, early in
Earth History.
• The first living
things were
simple bacteria
Modern bacterial mounds
en.wikipedia.org/wiki/Image:Stromatolites_in_Sharkbay.jpg
Fossil bacteria?
www.fas.org/irp/imint/docs/rst/Sect20/A12.html
http://en.wikipedia.org/wiki/Geologic_time_scale
3800-3500 million years ago
First Living Things: Bacteria
• The first living things were simple forms of life, anaerobic
bacteria, may have formed more than 3.6 billion years
ago (only 1 billion years after Earth was created).
• These life forms, also called cyanobacteria or “bluegreen algae”, did not require oxygen to breathe (as do
nearly all organisms inhabiting Earth at the present
time).
In the Sea (3): Oxygen
• Early photosynthetic
bacteria produced
oxygen and released
it as a waste product.
• This added oxygen
to the atmosphere
for the first time.
Iron oxide rocks
Photosynthetic
bacteria
http://www.globalchange.umich.edu/globalchange1/current/lectures/first_billion_years/bif.gif
en.wikipedia.org/wiki/Image:Anabaena_sperica.jpg
http://en.wikipedia.org/wiki/Geologic_time_scale
3800-3500 million years ago
Oxygen in the Atmosphere!
• Anaerobic, photosynthetic bacteria converted atmospheric
carbon dioxide (CO2) into oxygen (O2) and carbohydrates.
This made the evolution of more complex life forms
possible, including all animal life, that breathe oxygen and
feed upon plant carbohydrates.
In the Sea (4): Complex cells
• Two billion years later complex
eukaryote cells appeared.
• These had compartments with
special functions such as energy
factories called mitochondria.
• Eukaryote cells need oxygen this explains their late evolution
www.cushmanfoundation.org/resources/images/slide16.gif
1900 million years ago
http://en.wikipedia.org/wiki/Geologic_time_scale
In the Sea (5): Multicellular life
Grypania
• After another half billion years
many-celled life appeared
• Grypania was a coiled
tube, 2 mm wide and up to
5 cm long
© Bruce Runnegar with permission
http://en.wikipedia.org/wiki/Geologic_time_scale
1400 million years ago
Evolution of Oxygen Content of Earth’s Atmosphere