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7.0147.014
Lecture 16: Introduction to Lecture 16: Introduction to Ecology and the BiosphereEcology and the Biosphere
March 11, 2005March 11, 2005
Figure by MIT OCW.
MIT Department of Biology7.014 Introductory Biology, Spring 2005
Image is taken from NASA's Web site: http://www.nasa.gov.
Figure removed due to copyright reasons.Please see:figure 50.12a in Freeman, Scott. Biological Science. UpperSaddle River, NJ: Prentice Hall, 2002. ISBN: 0130819239.
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Figure removed due to copyright reasons.Please see:figure 50.12 in Freeman, Scott. Biological Science. UpperSaddle River, NJ: Prentice Hall, 2002. ISBN: 0130819239.
+2H
+2H
+2H
NN N
H
H
H
H H
N H
H H
N H
H H
NITROGEN FIXATION
Nitrogenase Enzyme Substrate, N2
Binding of Substrate
Reduction
Reduction
Reduction
Free Nitrogenase can Bind Another Molecule of N2 Release of
Product Product: Ammonia, NH3
N NN
N
NN
NN
NN
H
Figure by MIT OCW.
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ylightening
Industrial N fixation
100
140 biological
fixation
200 denitrification
SOIL
ATMOSPHERE
OCEANS
15 biological
fixation
110 denitrification
1200 internal cycling 8000
internal cycling 10
burial
36 river flow
groundwater
The Global Nitrogen Cycle Gigatons yr-1
<3 fixation b
11 GtGt ““gigatongigaton””
= 10= 1099 tonton= 10= 101515 gg= 1 billion= 1 billion
Industrial N fixation
100
140 biological
fixation
200 denitrification
SOIL
ATMOSPHERE
OCEANS
15 biological
fixation
140 denitification
1200 internal cycling 8000
internal cycling ?
burial
? river flow
<3 fixation by lightening
groundwater
Nitrogen “Cycle” Without Microbes
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Life on Earth Today: AbridgedLife on Earth Today: Abridged(Photosynthesis = Respiration)(Photosynthesis = Respiration)
CO2 + H2O carbon water dioxide gas
“CH“CH22O” +O” + OO22organicorganic oxygenoxygen carboncarbon (mass)(mass)
Plants Phytoplankton
Animals Bacteria
Chemical energy or
heat
Respiration
PhotosynthesisSolar energySolar energy
N,P,S,Fe….
Figure removed due to copyright reasons.Please see:figure 6.9, 7.10a, and 7.13 in Freeman, Scott. BiologicalScience. Upper Saddle River, NJ: Prentice Hall, 2002. ISBN:0130819239.
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Image is taken from NASA's Web site: http://www.nasa.gov.
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CO
CO
22 C
once
ntra
tion
in A
tmos
pher
e (p
arts
per
mill
ion)
Con
cent
ratio
n in
Atm
osph
ere
(par
ts p
er m
illio
n)
YearYear
P>RP>R
R >PR >P
Emergent PropertyEmergent Property
Image is taken from NASA's Web site: http://www.nasa.gov.
EARLYEARLY Life on Earth: AbridgedLife on Earth: Abridged(Photosynthesis > Respiration)(Photosynthesis > Respiration)
CO2 + H2O carbon water dioxide gas
“CH“CH22O” +O” + OO22organicorganic oxygenoxygen carboncarbon (mass)(mass)
Plants Phytoplankton
Animals Bacteria
Chemical energy or
heat
Respiration
PhotosynthesisSolar energySolar energy
N,P,S,Fe….
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( )
( )
0
1
2
3
4
2
2 2O 2 2
Metazoans
Dinosaurs
Modern Eukaryotes
Development of Ozone Shield
Oxygenic Phototrophs cyanobacteria
Anoxygenic Phototrophs photosynthetic bacteria
Origin of Life - 3.8 Billion Years Ago C
arbo
n B
uria
l Chemical Evolution
Formation of Earth 4.5 Billion Years Ago
21%
20%
10%
1%
0.1%
% O in Atmosphere Bill
ions
of Y
ears
Bef
ore
Pres
ent
Mar
ine
Orig
in
Ban
ded
Iron
Fo
rmat
ions
Terr
estri
al O
rigin
Red
Bed
s
Today: Release of Fossil Carbon
Prokaryotes Archaebacteria
Eubacteria Eukaryotes
CO + H "CH O" + O
Photochemical Synthesis
Figure by MIT OCW.
Figure removed due to copyright reasons.Please see:figure 25.7 in Freeman, Scott. Biological Science. UpperSaddle River, NJ: Prentice Hall, 2002. ISBN: 0130819239.
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Present Day Planetary Atmospheres Mars Earth Venus
CO2 95 % 0.035 % 98 %
N2 2.5 % 78 % 2 %
O2 0.25 % 21 % Trace
H2O 0.1 % 1 % 0.05 %
Temp (°C) -53 16 474 Adapted from Slesinger, W. 1991. Biogeochemistry: An Analysis of Global Change. Academic
Press. P.34
The same processes operate at all scalesThe same processes operate at all scales
CellCellBIOSPHERE
Figures removeddue to copyrightreasons.
Figure by MIT OCW.
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Molecular EcologyMolecular Ecology
Viewing the BiosphereViewing the Biosphereas a network of genesas a network of genes
A Sea of A Sea of OrgansimsOrgansimsA Network of GenesA Network of Genes
(“dissolved information”)(“dissolved information”)Is…
aaggttttaaaatt
aaggttttccccttaaaatt
ccccttaaaatt
ttccccttaaaatt
aaccccttaaaatt
aaggttttcc
aaggttccttaaaatt
aaggttttccaa
tt
aaggttttaaaatt
aaggttttcccctttt
aaggttttccccttaaaatt
aaggttcctta
aaatt
� 1 billion microbes per liter
� 99.9 % have not been cultivated
� information content of 1 liter = that in human genome
� most of unknown function
Cover of Wired Magazine featuring photo of Craig Venter,August 2004, removed due to copyright considerations.
Screenshots of the Sorcerer II web site have beenremoved due to copyright considerations.Please see:http://www.sorcerer2expedition.org/version1/HTML/main.htm
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Take Home Messages ¾ Ecology – life at different scales
¾ Emergent Properties
¾ Organism ↔ Environment TWO WAY
¾ Life has shaped Earth’s features
¾ Biosphere - geosphere have co-evolved
¾ Genetic inventory unknown
¾ Microbes Rule!
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