BIOSPHERE
The earth without life is an dynamic place,
active geologically and climatically, and
we assume all this complexity must be
consistent with scientific ideas.
But the world as it is now also differs
dramatically from what we would expect
from basic ideas of physics and chemistry.
Especially in the composition of the atmosphere.
Key question, are gases in ________________ or not?
CO2 - Carbon Dioxide
O2 - Oxygen
N2 - Nitrogen
Percent Composition of the Atmosphere
CO2
Venus
Mars
Earth
(w/o life)
Earth
(w/ life)
O2
N2
Oxygen gas (O2) is dangerously reactive
It can only be maintained by constant input
This altered atmosphere is visible from space
– altered _________________
Is something strange happening on earth?
If we look a little closer we see…
NASA
NASA
Viewed from space, much of the
planet has an unexpected greenish
appearance.
Of course, this is due to the
presence of
LIFE
in particular, ______________.
Global climate modelers refer to
this green layer in the biosphere
as the “__________”, a source of
annoying complication
Lithosphere + Hydrosphere + Atmosphere
+ LIFE
= _________________
2-9/2-8
Does the presence of life have
anything to do with the problem of
our bizarre atmosphere?
http://www.trekearth.com/gallery/Europe/Spain/Murcia/photo84564.htm
How is it possible that
something as humble as LIFE
could fundamentally alter
something as vast as the
atmosphere??
http://www.funnyjunk.com/p/david_goliath-jpg.html
How “big” is the atmosphere?
Hardly any air above
_____________
12-1
How deep is the hydrosphere?
Oceans cover about ___% of earth’s surface
Average depth – _____m (_______ ft)
Deepest depth – Mariana Trench, Western
Pacific - _________m (________ ft)
http://www.ocean.udel.edu/deepsea/level-2/geology/deepsea.html
How tall is the lithosphere surface?
Everest (Himalayas) is ______m
(________ ft)
http://www.caingram.info/Mount_everest.htm
So this zone where life
exists is about __ miles
thick
2-9/2-8
Earth is LARGE but Biosphere ______
Earth 8,000 miles in diameter
Ocean + atmosphere about 20 miles thick
20/8000 = 1/400
if earth 40cm, biosphere _____
Effectively two-dimensional
Like the “skin on an apple”
Or a soap bubble…
8,000
http://www.polarimage.fi/
Because the biosphere is “_____”, life
(including humans) can play important
roles in its dynamics
Global patterns of _____________ (CO)
http://www.gsfc.nasa.gov/gsfc/earth/terra/co.htm
_____________, which generates __________ as a by-product,
is the source of the __________-rich atmosphere on earth.
Major consequences of this
change include
- potential for ______________
- development of an _______
layer in the atmosphere
National Geographic
Sunlight in the upper
atmosphere interacts
with ___________ to
produce __________.
__________strongly
absorbs ___________
waves in the sunlight,
which are high energy
and potentially
damaging to living
organisms.
What is Life?
Biology is a branch of chemistry, and chemistry is the study
of the interactions among elements and molecules.
These interactions are generally formulated in terms of
______________________
For example, ozone involves the splitting of an
________molecule (___) into two _________ atoms
which then combine with other ________ molecules to
form ___________.
This interaction is expressed as
3__ => 2___
This is fairly simple because it only involves one element (__)
Generally reactions involve multiple elements and molecules
Reactants => Products
AB + CD => AC + BD
Some molecules have a strong tendency to react
together – they spontaneously react and release
energy – called _____________ reactions
Other reactions won’t run unless energy is
added, called ___________reactions
A key feature of a living organism is the capacity to transform
___________ in the environment (________, “________”) into
______ (_________________, “_________”)
The two essential classes of resource are
1. _________ 2. ______ (________)
These are essential resources for cells, energy is required to
drive_____________ (construction of life from elements).
The ultimate sources for these for most life today are
1. _______ – the sun, by photosynthesis
2. ____________ – earth, sea and air
The immediate source of this energy for all known living
systems are energy-rich organic molecules. “Organic”
refers to molecules based on _____________
C6H12O6
or
CH2O
The controlled “breakdown” of these molecules is
___________ (energy releasing) and coupled to
biosynthesis, which requires energy input (__________)
The key event in photosynthesis is when
___________, absorbed by pigments (e.g.
___________ – a green pigment), raise the
energy state of an _____________.
Through an intricate linked series
of reactions, the energy of this
______ is used to assemble sugar.
_______________ – light energy stored in sugar (see ch2)
CO2 + H2O + light = sugar + O2
Sugar is made from carbon dioxide
and water using light! This is often
called “__________ fixation”
____________ uses up ____ and releases ____
How does this reaction compare with the
anomalous atmosphere we see on earth?
C6H12O6
(reminder)
Photosynthesis uses up CO2 and releases O2
Percent Composition of the Atmosphere
CO2
O2
N2
Venus
Mars
Earth
(w/o life)
Earth
(w/ life)
What about nitrogen?
Most photosynthesis today produces oxygen (O2) as a
byproduct (water, H2O, is split to obtain the electron).
This is called “____________” photosynthesis.
Interestingly, there is an alternative pathway that doesn’t
split water, that “re-uses” electrons instead, called “______”
photosynthesis. Most photosynthesizers today do a small
portion of their photosynthesis via the _________ pathway.
It is likely that the ________
pathway evolved first. If that
mode had persisted, there
would be _________ in the
atmosphere today, _______.
Once oxygen increased in the atmosphere, life could
make use of its strong reactivity
Respiration (aerobic)
– energy in sugar used for metabolism
Sugar + O2 = Energy + CO2 + H2O
Both fire and respiration
have exactly the same
reaction equation – the
oxidation of carbohydrate
Respiration is sometimes called a “controlled burn”
where the energy is extracted in small steps to
maximize the useful ___________________.
Major biochemical pathways and processes in life today
Photosynthesis
– light energy stored in sugar
CO2 + H2O + light = sugar + O2
Respiration
– energy in sugar used for metabolism
Sugar + O2 = Energy + CO2 + H2O
Each is a complex chemical pathway
Carbon (& Oxygen) Cycle
Life has created new _________cycles in the biosphere
photosynthesis
O2
CH2O(sugar)
CO2, H2O
respiration
Photosynthesis and Respiration create a linked cycling
of _____________ between life and the atmosphere -and
also a link to the ____________________ cycle.
That these gases are relatively stable in the atmosphere suggests
that these two processes are in_______ – a _________________
Wait a minute!! If this is a balanced cycle, why
would CO2 ever go down and O2 up???
Current view - this is a result of_________of
photosynthetically fixed carbon in carboniferous
rocks and fossil fuels.
- shells of marine animals (______________)
create _________ rock like limestone under oceans
- accumulation of buried _______material on
land creates _____ fuels like coal, shale, petroleum
The “excess” ______ then accumulates in the atmosphere
This creates a longer term carbon cycle – the buried
carbon is not released until ____________ (______,
____) exposes these deposits to oxygen and weathering.
Carbon Fixation
C Deposition
C Uplift & Weathering
C Burial & Compression
It is estimated that this rock weathering combined with
volcanic activity are essential to replace the carbon lost by
burial – thus continued life depends on the
_____________ releasing this carbon
In brief, there is a fast carbon cycle and a slow carbon
cycle or maybe we should say slow and slower.
These two levels of cycling are well illustrated in this
figure, not so well in the current edition
2-20/2-26
The really striking fact here is how life has altered the
dynamics not only of the atmosphere, but of the
lithosphere as well – entirely new kinds of rock.
Biological & Geological regulation of CO2
Atmospheric CO2
Volcanoes
Geology
Uplift &
Weathering
Combustion
Biology
Photosynthesis
Respiration
Deposition & Compaction
Carbonaceous rocks
Fossil Fuels
Photosynthesis and respiration transform non-life into life using
material and energy. The relation between the two processes
expands our generalization about living systems
Light
Energy _____ through the system
(degraded to heat, light to space )
photosynthesis
O2
CH2O (sugar) CO , H O
2
2
respiration
Materials can ____ indefinitely
(are re-used)
Energy ______ the cycle
biosynthesis
heat
Light
End