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Chapter 1-2, 8

LIFESCI 2H03 Chapter Notes - Chapter 1-2, 8: Gaia Hypothesis, Global Warming, Positive Feedback

Life Sciences
Course Code
Rebecca Moumblow
1-2, 8

of 4
Textbook Reading
Chapter 1
Anthropogenic – human induced
Deforestation- clearing trees
Greenhouse gases: gases that warm earth’s surface by absorbing outgoing infrared
radiation and reradiating some of it back toward the surface. This is called greenhouse
Ozone layer protect Earth’s surface from UV
Global warming is warming of Earth’s atmosphere due to anthropogenic enhancement
of greenhouse effect
Earth system is a group of components that interact:
Atomsphere-thin envelope of gases the surrounds earth
Hydrosphere- reservoirs of water and ice
Biosphere- all living things
Solid earth – all rocks, mixture of crystalline materials called
Forests take in Co2 from atmosphere in summer, and give out CO2 in winter
Trace gases are less abdundant gases
Coal burning releases so2 which cools atmosphere but also causes acid rain, but
burning of coal releases co2 causing earth temp to increase more than cool
Arctic ice metling not affect sea level but the melting of land ice cap does
Stratosphere- where earth’s most ozone is located, from 10km to 50km in altitude and
the ozone in this layer absorbs suns harmful uv rays
Warmer sea temp causing stronger hurricanes
Chlorine breaks ozone layer and CFC reasons why we have ozone hole
Sun brightness (luminosity) gradually increase as it depletes hydrogen fuel
Gaia Hypothesis: states that Earth is self regulating system in which the biota play an
integral role
Chapter 2: Daisy World
Positive Coupling: a change ( increase or decrease) in one component is stimulus
leads to a change of in same direction to linked component
Negative Coupling: a change in one component leads to opposite direction change
Negative Feedback Loop- tends to diminish effects of disturbances
Positive feedback Loop- amplify the effects of disturbances
Equilibrium is stable
Valley is stable for ball and the peak is unstable because it wants to fall to valley to go
to equilibrium
Perturbation- temporary disturbance of system
Forcing- more persistent disturbance of a system
Albedo- reflectivity of a surface, darks surface absorb or reflect less -> low albedo
Daisy coverage increases more reflection causing temp to decrease
Decrease in daisy, decrese in albedo (+ coupling), leads to temp(- coupling)
Daisy have optimum temp so draw parabola
when put parabola and line on same graph but inverted axis the intersection point P1
and P2 represent shows the effect that daisy coverage on surface temperature and the
effect of that surface temp on daisy coverage
P1 and P2 are equilibrium points and represent couplings feedback loops
Teq ( change in temp of new equilibrium)= T0 + Tf shown on pg 39
Feedback Factor- ratio of equilibrium response to forcings to the response without
F= temp change with feedback Teq/ temp change without feedback T0
F only for stable systems 0 to 1 for negative systems and above 1 for positive systems
Chp 8: Recycling of the Elements: Carbon and Nutrient Cycles
Short term carbon cycle
Inflow to the atmospheric CO2 reservoir is the combination of the processes of
respiration and decomposition
Outflow from this reservoir is photosynthesis
Steady state- is condition in which the state of a system component is constant with
time. Infllow=outflow
When inflow exceeds outflow then atmospheric CO2 rises , outflow exceed inflow
then they drop
If more CO2 present, plants rapidly do photosynthesis thus decreasing CO2 levels
Residence time is average length of time a substance spends in a given reservoir that
is at steady state
Residence time= reservoir size at steady state/ inflow or outflow rate
Characteristic response time when system not at steady state
Oxidized carbon- carbon combined with oxygen
Reduced carbon- carbon that is combined with carbon, hydrogen or nitrogen
Photosynthesis: Co2+water-> carbs+ O2 gas
Biomass is total mass of organic matter in living organisms in particular reservoir. In
carbon, the total living biomass-combines biomasses of all primary producers and
consumers is about equal to the atmospheric carbon reservoir
Respiration is opposite of photosynthesis equation
Methanogensis is an anaerobic form of metabolism that involves multiple steps
carried out by different bacteria
Methanogensis: carbs-> Co2+ CH4
In O2, CH4 breaks into C and combines with 02 to make Co2
Sediment moved by dirt can move carbon to marine reservoir
Deep water has more O2 dissolved
Phytoplankton- dominant primary producers in ocean are free floating, photosynthetic
marine microorganism
Photic zone- uppermost part of the oceanic water column where there is sufficient
light for photosynthesis : open waters 100m and in shallow waters where clarity is
Most marine organic matter is decomposed by animals and microbes as it settles
through the water column. This decomposition releases Co2 ( product of both oxgen
breathing animals and microbial respiration) and nutrients to the oceanic deep waters.
Marine organisms nutrients lead to high rate of productivity if they are in appropriate
Overall effect of photosynthesis in shallow waters, of settling of organic matter, and
of decomposition in deep waters is transfer of CO2 and nutrients from the surface
water to deep ocean ( Pg 166)
Nutrients concentrations high in those parts where more dead organic matter present
Nutrient composition of world’s oceans dominated by production and decomposition
of organic matter
Long term Organic Carbon cycle
Continous supply of sediment to these basins leads to the burial of previously
deposited material, process continues sediments become buried to a depth of few
kilometers below seafloor lithified, waits until weathering liberates material to
Oxygen replenished by the leak of organic matter into sedimentary rock resveroir , for
every carbon one oxygen left behind because the O2 liberated during photosynthesis
of that carbon was not used during respiration or decomposition and gas remains in
Coal made from land basin at high temp and pressure, while petroleum made in
marine basins
Weathering is when O2 reacts with organic matter thus releaseing CO2 into
Inorganic Carbon Cycle
Limestone ( CaCO3) and dolomite sedimentary rocks carbon reservoirs
Ocean had low Co2 then atmosphere Co2 would diffuse or vice versa to keep balance
until humans activity changed
In water when Co2 dissolved you get H2Co3 carbonic acid
Use le chatleir and equilibrium laws
When pH increases then rxn shifts left
When pH decreases the rxn shifts left,
wollastonite is get hit by rain ( ph 5) then chemical weathering happens: calcium
carbonate+carbonic acid-> calcium ion + 2 bicarbonate ion
this neutralizes pH
silicate weathering: CaSi03(wollasotnite) + 2H2C03 -> Ca2+ + 2HC03 - + Si02 +
Silicate weathering consumes twice as much dissolved CO2 ( in form of carbonic
acid) as does carbonate weathering
Carbonate producing marine organisms remove Ca and HCO3- from seawater and
precipitate CaCO3, causes 2hc03- decrease reducing pH and by increasing
concentrations of dissolved CO2 in surface waters, carbonate producing organism
produce a CO2 gradient between the ocean and atmoshphere