MIT Department of Biology
7.014 Introductory Biology, Spring 2005
7.014
Lecture 16: Introduction to
Ecology and the Biosphere
March 11, 2005
Figure by MIT OCW.
1
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. Upper
Saddle River, NJ: Prentice Hall, 2002. ISBN: 0130819239.
2
Figure removed due to copyright reasons.
Please see:
figure 50.12 in Freeman, Scott. Biological Science. Upper
Saddle River, NJ: Prentice Hall, 2002. ISBN: 0130819239.
NITROGEN FIXATION
Nitrogenase Enzyme
Substrate, N2
N
N N
N
N N
H
Binding of Substrate
H
Reduction
+2H
N
N N
H H
Reduction
+2H
N N
H
H
Reduction
+2H
N N
Free Nitrogenase can Bind
Another Molecule of N2
Release of
Product
H
H
H
N
H
H
Product: Ammonia, NH3
N
H
Figure by MIT OCW.
3
The Global Nitrogen Cycle
1 Gt “gigaton”
gigaton”
Industrial
N fixation
100
=
=
=
109 ton
1015 g
1 billion
Gigatons yr-1
<3
fixation by
lightening
ATMOSPHERE
200
denitrification
140
biological
fixation
110
denitrification
36
river flow
15
biological
fixation
groundwater
1200
internal cycling
8000
internal cycling
10
burial
SOIL
OCEANS
Nitrogen “Cycle” Without Microbes
Industrial N
fixation
100
<3
fixation by
lightening
ATMOSPHERE
200
denitrification
140
biological
fixation
140
denitification
?
15
biological
fixation
river flow
groundwater
1200
internal cycling
8000
internal cycling
?
burial
SOIL
OCEANS
4
Life on Earth Today: Abridged
(Photosynthesis = Respiration)
Solar energy
Photosynthesis
Plants
Phytoplankton
CO2
+
H2O
carbon
dioxide gas
water
Chemical
energy or
heat
N,P,S,Fe….
“CH2O”
+
O2
organic
oxygen
carbon (mass)
Respiration
Animals
Bacteria
Figure removed due to copyright reasons.
Please see:
figure 6.9, 7.10a, and 7.13 in Freeman, Scott. Biological
Science. Upper Saddle River, NJ: Prentice Hall, 2002. ISBN:
0130819239.
5
Image is taken from NASA's Web site: http://www.nasa.gov.
6
CO2 Concentration in Atmosphere (parts per million)
Emergent Property
R >P
P>R
Year
Image is taken from NASA's Web site: http://www.nasa.gov.
EARLY Life on Earth: Abridged
(Photosynthesis > Respiration)
Solar energy
Photosynthesis
Plants
Phytoplankton
CO2
+
H2O
carbon
dioxide gas
water
Chemical
energy or
heat
N,P,S,Fe….
“CH2O”
+
O2
organic
oxygen
carbon (mass)
Respiration
Animals
Bacteria
7
CO2 + H2O
Today: Release of
Fossil Carbon
Dinosaurs
2
Development of Ozone Shield
Oxygenic Phototrophs
(cyanobacteria)
3
Anoxygenic Phototrophs
(photosynthetic bacteria)
10%
Prokaryotes
1%
Archaebacteria
Eukaryotes
Eubacteria
0.1%
Banded Iron
Formations
Modern Eukaryotes
Carbon Burial
Billions of Years Before Present
20%
1
Red Beds
21%
Metazoans
Marine
Origin Terrestrial Origin
0
"CH2O" + O2
% O2 in Atmosphere
Origin of Life - 3.8 Billion Years Ago
4
Chemical Evolution
Photochemical Synthesis
Formation of Earth 4.5 Billion Years Ago
Figure by MIT OCW.
Figure removed due to copyright reasons.
Please see:
figure 25.7 in Freeman, Scott. Biological Science. Upper
Saddle River, NJ: Prentice Hall, 2002. ISBN: 0130819239.
8
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 scales
Figures removed
due to copyright
reasons.
Cell
BIOSPHERE
Figure by MIT OCW.
9
Molecular Ecology
Viewing the Biosphere
as a network of genes
ag
tt
ca
t
Is…
A Network of Genes
(“dissolved information”)
agt
tc c
taa
t
ƒ 1 billion microbes per liter
ƒ 99.9 % have not been cultivated
c
tt
ag
ag
tta
at
ag t
ctaa
t
at
ta
ƒ information content of 1 liter = that in human genome
gt
t
taa
cc
a
tt
cc
t
t
ag
at
ta
c
t
ag
a c ct
aa t
ƒ most of unknown function
tc
ct
aa
t
at
ct a
ttc
ag
A Sea of Organsims
10
Cover of Wired Magazine featuring photo of Craig Venter,
August 2004, removed due to copyright considerations.
Screenshots of the Sorcerer II web site have been
removed due to copyright considerations.
Please see:
http://www.sorcerer2expedition.org/version1/HTML/main.htm
11
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!
13