Fundamentals of Ecology

1.018/7.
30J
Fundamentals of Ecology
Fall 2003
Lecture 1 Introduction to Ecology

READINGS FOR NEXT LECTURE:
Krebs Chapter 1: Introduction to the Science of Ecology
Redox Handout (please work through the example problems). (H, W)
Vernadskii (1926). The Biosphere. (H, W)
Rowe (1992). Biological Fallacy: Life Equals Organisms. (H, W)
Remmert (1980). Ecology: The Basic Concept. (H, W)
Outline for today:

I.
II.
III.
IV.
V.
What is ecology?
Why study ecology?
How to study ecology?
Where to study ecology?
How will we learn about ecology?
RECITATIONS NEXT WEEK

(9/8 and 9/11):
I. What is ecology?
origin of word:
oikos = the family household
logy = the study of
interesting parallel to economy = management of the household
many principles in common resources allocation, cost-benefit ratios
definitions:
Haeckel (German zoologist) 1870: By ecology we mean the body of knowledge concerning
the economy of Nature - the investigation of the total relations of the animal to its inorganic
and organic environment.
Burdon-Sanderson (1890s): Elevated Ecology to one of the three natural divisions of Biology:
Physiology - Morphology Ecology
Andrewartha (1961): The scientific study of the distribution and abundance of organisms.
Odum (1963): The structure and function of Nature.
Definition we will use (Krebs 1972):
Ecology is the scientific study of the processes regulating the distribution and
abundance of organisms and the interactions among them, and the study of how these
organisms in turn mediate the transport and transformation of energy and matter in the
biosphere (i.e., the study of the design of ecosystem structure and function).
The goal of ecology is to understand the principles of operation of natural systems and to
predict their responses to change.
1
What ecology is not

Ecology is not environmentalism, nor deep ecology. Ecology is science, based on biological,
physical and chemical principles, and should be value-free. Environmentalism advocates for certain
actions and policy positions.
II.
Why study ecology?
Curiosity How does the world around us work? How are we shaped by our surroundings?
Responsibility How do our actions change our environment? How do we minimize the detrimental
effects of our actions? Overfishing, habitat destruction, loss of biodiversity, climate change.
Nature as a guide The living world has been around much longer than we have and has solved
many problems with creative solutions. Ecological systems are models for sustainability. How can we
feed our growing population? Where will we live?
Sustainability a property of human society in which ecosystems (including humans) are managed
such that the conditions supporting present day life on earth can continue.
Ecology helps us understand complex problems.
Examples:
Cane toads in Australia
Feral pigs in Hawaii
Nile Perch in Lake Victoria
Wolves in Yellowstone
III. How to study ecology?

What kinds of experiments do ecologists perform?
Observations Go into the field and see whats happening
Microcosms Isolate a portion, limit factors, manipulate conditions.
Mathematical models Describe ecosystems interactions as equations.
Connections to other
disciplines :
Genetics
(7)
Hydrology
(1)
Physiology
(5,7)
ECOLOGY
Biochemistry
(5,7)
Behavior
(7,9)
adapted from Elements of

Ecology, R.L. Smith and
T.M. Smith, 4th Ed.
Atmospheric
sciences
(1,12)
Geology
(12)
IV. Where to study ecology?

Organism
(Tissues)
Organelle
Molecule
Atom
Population: Group of interacting and interbreeding organisms.

Community: Different populations living together and interacting.
Populations can interact as competitors, predator and prey, or symbiotically.
Ecosystem: Organisms and their physical and chemical environments together in a particular area.
The smallest units that can sustain life in isolation from all but atmospheric surroundings.
Biome: Large scale areas of similar vegetation and climatic characteristics.
Biosphere: Thin film on the surface of the Earth in which all life exists, the union of all of the
ecosystems. This is a highly ordered system, held together by the energy of the sun.
When is an organism not an organism?
Populations are shaped by their abiotic surroundings, and, in turn, change their abiotic surroundings.
For example, O2 in atmosphere from photosynthesis. Others?
These levels of organization do not exist in isolation. There are feedbacks between the largest and
smallest scales.
Interactions among different levels lead to emergent properties.
Principle of hierarchical control (Odum): As components combine to produce larger functional wholes
in hierarchical series, new properties emerge. That is, one cannot explain all the properties at one
level from an understanding of the components at the one below.
V. How will we learn about ecology?

Start with energy flows
At the individual level, how do organisms make a living?
At the ecosystem level, how does energy move around?
Move on to nutrients
How does nutrient availability limit organism growth?
On an ecosystem and global scale, how do organisms fit in to global nutrient cycles?
Then focus on populations and communities
Numerical models of the growth of individual populations
Then apply these to model competition between populations for the same resources
Metrics of species diversity and responses of communities to changes
3
Study questions
Give an example of organisms modifying their surroundings (not mentioned in class).
What is the relationship between ecology and environmentalism? Where does Remmert see
ecology fitting in to broader societal problems?
Why does Remmert call green plants the first great polluters of the environment?
What is an invasive species? Why do they pose such a serious problem for ecologists?
Give an example of an ecosystem, and explain what the associated community would consist of.
What kinds of experiments do ecologists perform? What are the advantages and disadvantages
of each?
According to Vernadskii, in what ways does life change the surface of the earth. If all forms of life
became extinct, what would happen? What does he mean by the biosphere is the creation of the
sun? and Under the thermodynamic conditions of the biosphere, water is a powerful chemical
agent... but on a dead Earth, water is ...a compound of weak chemical activity?
Rowes Biological Fallacy calls in to question using an organism-level perspective on life.
Describe how energy flows would look different if you were a) inside a cell or b) in a space ship
looking down on earth. Without prior knowledge, what would you call life?
1.018/7.30J
Fall 2003
Lecture 2 Carbon and Energy Transformations

Krebs Chapter 25: Ecosystem Metabolism I: Primary Productivity
Luria. 1975. Overview of photosynthesis. (H, W)
Stowe, S. 2003. When swans inspire not a ballet, but a battle. NY Times. September 3. (H,W)
Kaiser, J. 1995. Can deep bacteria live on nothing but rocks and water? Science. 270:377. (L)
Stevens, TO and JP McKinley. 1995. Lithoautotrophic microbial ecosystems in deep basalt
aquifers. Science. 270: 450. (L)
Pace, N. 1997. A molecular view of microbial diversity and the biosphere. Science. 276:734. (L)
Newman, DK and JF Banfield. 2002. Geomicrobiology: How molecular-scale interactions
underpin biogeochemical systems. Science. 296:1071. (L)
Sarbu, S et al. 1996. A chemoautotrophically-based cave ecosystem. Science. 272:1953. (L)
Nature has put itself the problem of how to catch in flight light streaming to earth and
to store the most elusive of all powers in rigid form.
Mayer, 1842, discovered law of conservation of energy
Outline for today:
I. Evolution
II. Autotrophs
A. Photosynthesis
B. Bacterial photosynthesis
C. Chemosynthesis
III. Heterotrophs
A. Aerobic respiration
B. Fermentation
C. Anaerobic respiration
Main question: How do organisms obtain carbon and energy needed to grow and function?
I. Evolution
Old view of the world: 5 Kingdoms.
Development of new perspective on life.
Novel genetic identification techniques (C Woese in the 1970s)
Tree of Life with 3 Domains: Eubacteria, Archaea, Eukaryotes
Hydrothermal vents and hot springs
Genotypic not phenotypic classifications
Universal phylogenetic tree based on SSU rRNA sequences

Sixty-four rRNA sequences representative of all known phylogenetic domains were aligned, and a
tree was produced using FASTDNAML (43, 52). That tree was modified, resulting in the composite
one shown, by trimming lineages and adjusting branch points to incorporate results of other analyses.
The scale bar corresponds to 0.1 changes per nucleotide. (Pace, N. 1997. Science. 276:734-740)
Dinosaurs
21%
Modern eukaryotes
Development of
ozone shield
20%
Carbon burial
Billions of years before present
Metazoans
Oxygenic phototrophs
(cyanobacteria) Prokaryotes
3
Anoxygenic phototrophs
(photosynthetic bacteria)
10%
01%
00.1%
Archaebacteria
Eukaryotes
Eubacteria
Marine
origin
Terrestrial origin
Banded iron
Red beds
formations
Today: Release of
fossil carbon
% 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 2. Adapted from Brock and Madigan, Biology of Microorganisms. Major landmarks in
biological evolution.
Basic picture of life:

CH2O and O2
Heterotrophs
nourished from others
Autotrophs
self-nourishers
CO2 and H2O

II. Autotrophs
These self-nourishers get their energy from the sun (photoautotrophs) or from reduced inorganic
compounds (chemoautotrophs), and they get their carbon from CO2.
These organisms undergo two reactions. The first reaction produces ATP* and NADPH**, which
provide stored energy and reducing power. For photosynthetic organisms, this is known as the Hill
reaction. The second reaction, the Calvin Cycle, is common to all autotrophs, and uses stored energy
and reducing power to convert CO2 to CH2O (sugar).
A. Photosynthesis (aerobic)
Who? Plants, cyanobacteria, eukaryotic algae
C Source? CO2
Energy Source? Sunlight
Electron Donor? H2O
Where? In aerobic, light conditions
CO2 + H2O + h
X CH2O + O2
B. Bacterial Photosynthesis (anaerobic)

Who? Bacteria (e.g. Purple sulfur bacteria)
C Source? CO2
Energy Source? Sunlight
Electron Donor? H2S
Where? In anaerobic, light conditions
CO2 +2 H2S + h
X CH2O + 2 S + H2O
C. Chemosynthesis
Who? Chemoautotrophic bacteria, aka chemolithoautotrophs
C Source? CO2
3
Energy Source? Reduced inorganic compounds (CH4, NH4, H2S, Fe2+)

Electron Donor? Reduced inorganic compounds
Where? In microaerobic or anaerobic, dark conditions
Sulfur oxidizing bacteria:
Methanotrophs:
Nitrifying bacteria:
Iron oxidizing bacteria:
H2S S SO42-
CH4 (methane) CO2
NH4+ NO2- NO3

Fe2+ Fe3+
ATP = adenosine triphosphate. (ADP = adenosine DI phosphate)

NADPH = nicotinamide adenine dinucleotide phosphate
**
III. Heterotrophs
These organisms (nourished by others) get their energy and carbon from reduced organic
compounds.
ATP and NADH*** are produced, which can then be used elsewhere in the cells.
A. Aerobic respiration
Who? Aerobic eukaryotes and prokaryotes
C Source? CH2O
Energy Source? CH2O
Electron Acceptor? O2
Where? Aerobic conditions
These reaction is essentially the reverse of the Calvin cycle. O2 is the final electron acceptor. Plants
also carry out this reaction to get energy for their growth and metabolic processes.
CH2O + O2
X CO2 + H2O
B. Fermentation
Who? Eukaryotes and prokaryotes
C Source? CH2O
Energy Source? CH2O
Electron Acceptor? organic compounds
Where? Anaerobic conditions
This is only the first part of respiration and results in partial breakdown of glucose. The products are
organic acids or alcohols (e.g., lactic acid, ethanol, acetic acid) rather than CO2.
C. Anaerobic respiration
Who? Prokaryotes only
C Source? CH2O
Energy Source? CH2O
Electron Acceptor? Oxidized inorganic compounds (SO42-, Fe3+, NO3+, etc.)
Where? Anaerobic conditions
Very similar to aerobic respiration, except that O2 is not the final electron acceptor. Instead, another
oxidized compound such as SO42-, NO3-, or CO2 is the final electron acceptor.
Iron reducing bacteria:
Denitrifying bacteria:
Sulfate reducing bacteria:
Methanogens:
Fe3+ Fe2+
NO3- NO2
NO2- N2
H2S S SO42-
CO2 CH4 (methane)
***
NADH = nicotinamide adenine dinucleotide (a relative of NADPH. NADH is used for ATP
production, while NADPH is associated with biosynthesis)
Study Questions:
What is a Winogradsky column? What are the light, oxygen and sulfide levels in each layer, and
which organisms dominate each layer? What are the energy and carbon sources for each kind of
organism?
Describe the significance of the discovery of deep-sea hydrothermal vents.
Why has Rubisco been called the most important protein on Earth?
What is unique about the cave ecosystems described in Sarbus article? What are the differences
and similarities to hydrothermal vents?
Banfield and Newmans article mentions the benefits of advances in genetic techniques for
understanding microbial community structure and the identities of microorganisms. Given what
you know about metabolic diversity, why is it so hard to culture most microorganisms in a
laboratory?
If a lake is covered in algae, how do anoxygenic photosynthetic bacteria, which live underneath
the algae, manage to obtain sufficient light to carry out photosynthesis?
1.018/7.30J
Fall 2003
Lecture 3 Primary Productivity

Krebs. Pages 97-102: Light as a Limiting Factor.
Broad, WJ. 2003. Deep under the sea, boiling founts of life itself. NY Times. 9/9 (H,W)
Behavior
Field, CB et al. 1998. Primary production of the biosphere: Integrating terrestrial and
(7,9)
oceanic components. Science. 281:237-240. (H,W)
Noble IR and R Dirzo. 1997. Forests as human-dominated ecosystems. Science.
277:522-525.
Questions for today:

How do energy and carbon move through ecosystems?
How do terrestrial and aquatic ecosystems vary?
What limits their productivity?
Outline:
I. Scale
II. Definitions
A. Terms to describe productivity
B. Residence times and turnover rate
III. Distribution on the Earth
IV. Terrestrial Productivity
A. Limiting factors
B. Measurement
MOVIE NIGHT:
Monday 9/15 @ 7:30pm
Cane Toads
I. Scale
(A) Metabolism of a Cell
(B) Metabolism of a Drop of the Ocean
CO2
ADP
NADP
CO2
CH2O
O2
ATP
H2 O
NADPH
Chloroplast
GROWTH
O2
DNA
Nucleus
[CH2O]
Dissolved
Organic
Carbon
NADH
CH2O
CO2
ATP
NAD
1 mm
CO2
CO2
Energy
Biological Work
O2 - Motility
- Biosynthesis
- Transport
- Electrical Potential
- Light Emission
ADP
Inorganic
Nutrients
N,P,Fe,S etc
CO2
Inorganic
Nutrients
O2
Mitochondrion
1 m
(C) Metabolism of an Ocean
Solar
Phytoplankton
O2
CO2
Animals
[CH2O]
700
Plants
Remineralized
Nutrients
O2
CH2O
Recycled
Inorganic
Nutrients
O2
O2
Mixed
Layer
O2
100m
CH2O
Zooplankter
Fecal pellets
[CH2O]
600
Inorganic
Nutrients
40,000
Deep Sea Sediments

Upwelled
Inorganic
Nutrients
4000m
Carbon inventory
x 1015g C
II. Definitions
A. Terms to describe Productivity
gross primary productivity (GPP) = rate of conversion of CO2 to organic carbon per unit surface area
Units: g C m-2 year-1, or Kcal m-2 year-1
gross primary production has units of g C year-1 for a lake, forest, field, etc.
respiration by autotrophs (RA) = how much energy or carbon is used for plant metabolism
net primary production (NPP) = GPP RA = how much energy or carbon is stored as biomass
respiration by heterotrophs (RH) = how much energy or carbon is used for heterotroph metabolism
net community production (NCP) = GPP RA RH = NPP RH
photosynthetic efficiency (PE) = 100*(incident radiation converted to NPP)/(total incident radiation)
n.b. Were using energy and (reduced) carbon interchangeably. Conversion: 39 kJ per g C
B. Residence times and turnover rates

f = flux (mass/area/time). use GPP (how much is entering the system)
M = mass (biomass/area)
Mean residence time (MRT) = M/f = (g/m2) / (g/m2/year) = years
Fractional turnover (k) = 1 / MRT * 100 = % turning over each year
Study Questions:
1. What is the difference between net and gross primary productivity? What is the difference between net
community productivity and net primary productivity? How would you measure these difference?
2. What regulates primary productivity in terrestrial? How is this reflected in the global distribution of primary
production?
3. What is the turnover rate in a forest? What does it signify? How is it measured?
4. What is functionally and physiologically similar about phytoplankton and trees? What is different?
5. How will increases in atmospheric CO2 affect global productivity?
6. Discuss the principles behind remote sensing to terrestrial productivity. What limits the quality of the data?
7. Describe 2 strategies plants have developed to deal with low water availability.
8. According to Noble and Dirzo, human domination of forests extends beyond plantations and actively
managed lands. In what other ways do humans alter forest ecosystems, and how do the authors
recommend minimizing the detrimental impacts?
Adapted from: Begon,1996
Comparison of Young and Mature

Forests
Biomass (kg m-1)
NPP (g m-2 y -1)
% mass in
Wood
Leaves
Roots
Turnover time (y)
Tree age (y)
Respiration/GPP
Young
9.7
1060
Mature
58
1300
60
10
30
8.5
4045
0.80
80
1
19
43.5
150400
1.00
N ET
Ecosystems (in order

of productivity)
RIMARY
Area
6
2
(10 km )
TABLE 23.1
P LANT B IOMASS OF W ORLD E
RODUCTION AND
Mean net primary

production per unit area
2
(g/m /yr)
COSYSTEMS
World net primary

production
9
(10 mtn/yr)
Continental
Tropical rain forest
Tropical seasonal forest
Temperate evergreen forest
Temperate deciduous forest
Boreal forest
Savanna
Cultivated land
Woodland and shrubland
Temperate grassland
Tundra and alpine meadow
Desert shrub
Rock, ice, sand
Swamp and marsh
Lake and stream
Total continental
17.0
7.5
5.0
7.0
12.0
15.0
14.0
8.0
9.0
8.0
18.0
24.0
2.0
2.5
149.0
2000.0
1500.0
1300.0
1200.0
800.0
700.0
644.0
600.0
500.0
144.0
71.0
3.3
2500.0
500.0
720.0
34.00
11.30
6.40
8.40
9.50
10.40
9.10
4.90
4.40
1.10
1.30
0.09
4.90
1.30
107.09
Marine
Algal beds and reefs
Estuaries
Upwelling zones
Co ntinental shelf
Open ocean
Total marine
World total
0.6
1.4
0.4
26.6
332.0
361.0
510.0
2000.0
1800.0
500.0
360.0
127.0
153.0
320.0
1.10
2.40
0.22
9.60
42.00
55.32
162.41
Mean biomass
per unit area
2
(kg/m )
44.00
36.00
36.00
30.00
20.00
4.00
1.10
6.80
1.60
0.67
0.67
0.02
15.00
0.02
12.30
2.00
1.00
0.02
0.01
0.003
.01
3.62
Source: Smith, 2001.
Vegetation
Reflectance
40
30
Atmospheric
absorption
TM 4
Atmospheric
absorption
50
TM 5
TM 7
TM TM TM
1 2 3
Bare soil
20
10
0.4
0.6
Visible
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4 m
Near Infrared
Wavelength
A portion of the solar spectrum showing the typical reflectance from soil (-----) and leaf (- - - - )
surfaces and the portions of the spectrum that are measured by the LAND-SAT satellite.
Adapted from: Schlesinger, 1997.
9
8
Near ir / red reflectance
TM4 / TM3
7
6
y=1.92 x (0.583)
5
R2 = 0.91
4
3
2
1
0
10
12
14
16
18
Leaf area index (m2/m2)

Adapted from: Schlesinger, 1997.
Net primary production

(g m-2 yr-1)
1500
1000
500
10
15
20
LAI
NPP is directly related to leaf-area index (LAI)
for forests in the northwestern United States
Adapted from: Smith, 2001.
Net productivity above ground per year (g/m2)
3000
2000
1000
200 400 600 800 1000 1200

Actual evapotranspiration (mm)
Adapted from Krebs
NPP (nmol CO2 g-1 s-1)
700
600
Desert herbs
Old field herbs
Deciduous chaparral shrubs
Evergreen shrubs and trees
+ South African shrubs
x
500
400
x
x
300
200
100
0
+ +
++
+
1.0
2.0
3.0
Leaf nitrogen (mmol g-1)
4.0
Terrestrial NPP Co-opted by Humans

Source
Cultivated Land
NPP Co-opted (Pg)

15.0
Grazing Land
Converted Pastures
9.8
Consumed on natural grazing lands
0.8
Burned on Natural Grazing Lands
1.0
Subtotal
11.6
Forest Land
Killed during harvest
1.3
Shifting Cultivation
6.1
Land Clearing
2.4
Forest plantation productivity
1.6
Forest harvests
2.2
Subtotal
13.6
Human Occupied Areas
0.4
Total Terrestrial NPP Co-opted
40.6
Total Terrestrial NPP
132.1
Percent Co-opted
30.7%
Source: Vitousek at al. 1986 Bioscience 36:368
1.018/7.30J
Fall 2003
Lecture 4 Primary Productivity in Aquatic Ecosystems

Chisholm, SW. 1992. What limits phytoplankton growth? Oceanus. 35:36-46. (H,W)
Falkowski, PG. 2002. The oceans invisible forest. Scientific American. 287:38-45. (H,W)
Raloff, J. 2003. Zebra mussels to the rescue. Science News. 163:365. (H)
Perkins, S. 2003. Slow turnover: Warming trend affects African ecosystem. Science
News. 163:404. (H)
Outline for Today:

I. Review Global Distribution
II. Measurement techniques
III. Limiting factors for freshwater and marine systems
A. Light
B. Nutrients
1. Distribution and availability
2. Biological requirements (next class)
Study Questions
1. Explain why light tends to be more limiting in freshwater or coastal systems than in the open
ocean.
2. Explain the concept of a limiting nutrient. How would you design an experiment to determine
which nutrient is limiting in a particular system?
3. What are the challenges associated with using uptake of 14CO2 to measure primary productivity?
4. Why are phytoplankton so much more productive (on the basis of biomass) than land-based
plants? Approximately how much do phytoplankton and land-based plants contribute to global
primary productivity?
5. Why did scientists used to think that phosphorus, rather than nitrogen, should be the limiting
nutrient in oceans? Why is nitrogen often the limiting nutrient instead? And what role does Fe
play in nitrogen limitation in oceans?
6. Both Chisholm and Falkowski explain how adding iron to the worlds oceans may enhance their
primary productivity, but caution against taking drastic actions on a large scale. Why would the
addition of iron enhance productivity? Why might this not be a panacea for elevated atmospheric
CO2 levels?
Aquatic ecosystem
RA
GPP
RH
phytoplankton
200m
NPP
zooplankton
bacteria
fish
Thermocline
3000m
NCP
About 15% NPP falls below the

thermocline. Less than 1% makes it
to the sea floor
Relative Light Intensity (I/Io)

0
0.2
0.4
0.6
0.8
Z
Depth (m)
20
k = 0.1
40
k = 0.02
60
dI/dt = -kZ
I=Ioe-kZ
80
100
Io
Photosynthesis as a function of depth for 3 kinds of lakes
Rate of Photosynthesis
0
20
40
60
2.5
7.5 10
0.1
0.2
0.3
10
10
20
20
Depth (m)
Depth (m)
Depth (m)
10
2
20
Depth (m)
30
40
30
40
3
Eutrophic
(Clear Lake)
4
Photoinhibition
(Castle Lake)
30
50
Oligotrophic
(Lake Tahoe)
60
data modified from Krebs Figure 25.5
50
60
20
40
60
North Pacific Central Gyre
Temperature
(oC)
Depth (m)
10
0
15
20
Nitrate
(m/L)
Phosphate
(m/L)
25 0 0.2 0.4 0.6 0.8
9 12
Chlorophyll
(m/L)
Primary production
(mgC/m3/half-day expt.)
0 0.1 0.2 0.3 0
100
1% Light level
200
Zc
300
Adapted from: Krebs Figure 25.7
Thermal stratification in lakes
Depth
Nutrients
Temp
Wind
Epilimnion
(well-mixed,
nutrient-poor)
Thermocline
Hypolimnion
(often O2 depleted
nutrient-rich)
But, lakes dont usually look this way year-round
1.018/7.30J
Fall 2003
Lecture 5 Limiting Nutrients and Redfield Ratio

Krebs. Chapter 26. Ecosystem Metabolism II: Secondary Production
Nemani RR et al. 2003. Climate-driven increases in global terrestrial net primary
production from 1982 to 1999. Science. 300:1560-3. (H,W)
REMINDER:
From last class:

A few more thoughts on terrestrial primary productivity
How to integrate all the aspects we talked about?
Problem Set 1 Due next

Tuesday during lecture.
No late problem sets please!
While one factor may dominate, many factors involved:
NPP = f(NPPmax, PAR, LAI, T, CO2, H2O, NA)

Where:
NPPmax
PAR
LAI
T
[CO2]
H2O
NA
= maximum for given ecosystem/vegetation type

= photosynthetically active radiation
= leaf area index
= temperature
= atmospheric CO2 concentration
= soil moisture
= index of nutrient availability
How does climate change affect each of these parameters?

For instance, atmospheric CO2. If [CO2] continues to increase, will this increase global NPP? GPP?
Some things to consider:
Experiments have shown increases in plant biomass with increased atmospheric CO2.
Over the past 100 years, the annual rings of tree trunks have not gotten thicker.
Leaves from olive branches in King Tuts tomb have a higher density of stomates than leaves
of olive trees in modern-day Egypt. Other studies have shown decreased stomatal density
since the Industrial Revolution. What does this mean for water use efficiency?
Productivity?
If global temperatures increase 1C, or 3C, how will this change global NPP? GPP? Consider:
Effect of higher temperature on plants, on animals, and on bacteria that feed on detritus.
Effect of higher temperatures +/or higher CO2 on the distribution of C3 vs. C4 plants.
What is a limiting factor? On what time scale? Limiting for whom?
Limiting nutrient analogy: Baking cookies

Recipe:
3 cups flour
0.5 cup eggs
2 cups sugar
0.1 cup baking soda
1 cup butter
Questions:
If you start with equal amounts of all ingredients, which one is the limiting?
If someone brings you more of that ingredient, which ingredient will now be
limiting?
If you start with 60 cups of flour, 50 cups of sugar, 10 cups of butter, 10 cups of
eggs and 2 cups of baking soda, which ingredient will be limiting?
Canadian Research and Development Magazine 1970:

Has the international joint commissionbeen a party to what
may prove to have been the most incredible scientific/political
hoax in the history of Canadian and American Relations?
What hoax? Do you believe phosphates are the key nutrient
in the process of eutrophication? You are wrong! You have
hung phosphates without a fair trial.
Proctor and Gamble:

The problem of man-caused eutrophication is the most
complex subject in our world. It truly encompasses the
mystery of life on earth. Thus we are attempting to
understand and answer the questions: Why do plants grow?
How can we retard or stop their growth?
Northwestern Ontario Experimental Lake 226
N + C added
N + C + P added
Image courtesy of Oceans and Fisheries, Canada.
http://www.dfo-mpo.gc.ca/home-accueil_e.htm
Note: image usage policy: http://www.dfo-mpo.gc.ca/copyright/copyright_e.htm
Schindler
September 4, 1973
Pollution and Recovery in Lake Washington
Adapted from
Krebs Figure 23.24
Source: Edmondson,1991 (Figure 1.8)
Adapted from Krebs Figure 25.14
Change in growth rate

Following nutrient addition
Marine phytoplankton samples

0.25
0.20
0.15
0.10
0.05
0.00
-0.05
Nitrogen
Iron
Silica
Phosphorous
Adapted from Krebs Figure 25.9
1.018/7.30J
Fall 2003
Lecture 6 Introduction to Secondary Productivity

Krebs. Chapter 23 pages 463-469. Food Chains and Trophic Levels
Guterl, F. 2003. Troubled seas: Ninety percent of the big fish have already been caught.
Newsweek. July 14 edition, p 46. (H,W)
Pauly D and V Christensen. 1995. Primary production required to sustain global fisheries.
Nature. 374:213-4. (H,W)
REMINDER:
Pre-proposal due Thursday!
No late proposals!
MOVIE NIGHT:
Re-showing of Cane Toads
Thursday, 8pm
Food provided
The last few lectures, we have focused on primary productivity. As we saw previously, autotrophs are
able to capture 1-2% of the incoming solar radiation.
We are now going to explore what happens to the energy stored in autotrophic biomass. Secondary
productivity is defined as the rate of biomass accumulation by heterotrophs (herbivores, carnivores
and detritivores).
For trophic level n:

Rn
An
In
Pn
Pn-1
Fn
NU =
not used
biomass
biomass
Pn-1 = Productivity at trophic level n-1

NU = Productivity from trophic level n-1
not used by trophic level n
= Amount of energy ingested
Fn
= Amount of energy lost as fecal matter

(but available to detritivores)
An
Dead organic matter

compartment of
decomposer system
In
= Amount of energy assimilated

(i.e. available for metabolism)
Rn
= Amount of energy lost to respiration
Pn
= Productivity of trophic level n

(evident as growth and reproduction)
Study questions
1. What is the real truth to Dogberts insights? What is the wasted step?
2. Define a trophic level. What are the difficulties in assigning a species to a single trophic level?
3. Describe the difference between exploitation, assimilation and production efficiencies. What are the typical
ranges of each of these efficiencies? How do they combine to give an overall ecological efficiency?
4. According to the Newsweek article, what are the consequences throughout the marine food web of
overfishing of top predator fish?
5. According to Pauly and Christensens article, how much of aquatic primary productivity is required for the
amount of fish caught annually? How does this number differ between freshwater and marine systems?
Why does it seem unlikely that humans will be able to harvest much more of the worlds aquatic productivity
than is already being harvested?
N : P
20 : 1
Correlation between the concentration of nitrate and phosphate in

waters of the Atlantic, Indian, and Pacific Oceans
Source: Redfield, 1934
C : N
7: 1
Western Atlantic
Units:
[NO3]=10-3 millimols per liter
[CO3]=10-2 millimols per liter
Western Atlantic
Deep
Water
Samples
O2 : N
6: 1
Units:
REDFIELD HYPOTHESIZED:
The proportions of elements in the
atmosphere and the sea are controlled by the
biogeochemical cycle
NO3 + PO4 + O2
CO2 + PO4 + NO3
Living Organisms + O2
Dead Organisms + O2
Deep
Sea
If the elemental composition of the deep ocean water is dictated by the

composition of the plant material, the elements should vary in constant
proportion from place to place.
100% Saturation
O2
1) O2 between surface and

Mixed
minimum is `the amount
Layer
used to oxidize the
organic compounds as
they settle out of the
euphotic zone
O2 Minimum
Depth
2) Measured N:P:C ratios in

mid-ocean, surface and deep
ocean at various times
PO4
NO3
Adapted from
Krebs Fig. 23.3
Adapted from: Odum (1972)
From Smith
and Smith
2001
Assimilation Efficiencies (A/I)

for different types of organisms
Herbivore
Carnivore
Microbivore
Saprotroph
Invertebrates
40%
80%
30%
20%
Vertebrates
50%
80%
--
--
From Heal and Mac Lean, 1975
The more similar you are to your food, the more efficient you are at assimilating it
Microbivore = an organism that feeds on microorganisms

Saprotroph = a fungus that feeds on detritus
Production Efficiency of Various Animal Groups

(ranked in order of increasing efficiency)
Group
P /A %
1 Insectivores
0.86
2 Birds
1.29
3 Small Mammal Communities
1.51
4 Other Mammals
3.14
5 Fish and social insects
9.77
6 Non-insect invertebrates
25.0
7 Non-social insects
40.7
Non-insect invertebrates
8 Herbivores
20.8
9 Carnivores
27.6
10 Detritivores
36.2
Non-social insects
11 Herbivores
38.8
12 Detritivores
47.0
13 Carnivores
55.6
Source: Begon (1996)
Courtesy of Eli Meir. Used with permission.
Cod
Bottom-dweller but stays relatively close to the surface (within

a few hundred meters).
Can reach up to 200 pounds and live 20 - 30 years
Large females can lay 10 million eggs / year

Eats anything that moves and is smaller than mouth
Cod Fishing
When Columbus sailed, 1000 Basque ships were fishing

Georges Bank and Newfoundland.
If 1/2 of these were in Georges Bank and each ship pulled
in 20 tons of cod, catch was about 10,000 tons / year.
By mid 1500s, 60% of fish eaten in Europe were cod.
Recipe book of Charles V in France
Salt cod is eaten with mustard sauce or with melted

fresh butter over it.
- Guillaume Tirel, Le Viandier, 1375
Cokkes of Kellyng
Take cokkes of kellyng; cut hem smalle. Do hit yn a
brothe of fresch fysch or of fresh salmon; bowle hem
well. Put to myllke and draw a lyour of bredde to hem
with saundres, safferyn & sugure and poudyr of pepyr.
Serve hit forth, & otheyr fysch amonge: turbut, pyke,
saumon, chopped & hewn. Sesyn hem with venyger &
salt.
-anonymous manuscript from fifteenth century
How Much Cod Can Be Caught?
From Pauly and Christensen

See text 546-547
TABLE 2 Global estimates of primary production (PP), of PPR to sustain world fisheries (mean for 1988-1991,
net weight), and of the mean trophic levels (TL) of the catches, by ecosystem type
PPR (catches +discards)
Ecosystem
type
Area
(106 km2)
PP
(gC m-2 yr-1)
Catch
(g m-2 yr-1)
Discards
(g m-2 yr-1)
TL of the
catch
Mean
(%)
95%
Confidence
interval
Open ocean
332.0
103
0.01
0.002
4.0
1.8
1.3-2.7
Upwellings
0.8
973
22.2
3.36
2.8
25.1
17.8-47.9
Tropical
Shelves
8.6
310
2.2
0.671
3.3
24.2
16.1-48.8
Nontropical
shelves
18.4
310
1.6
0.706
3.5
35.3
19.2-85.5
Coastal/reef
systems
2.0
890
8.0
2.51
2.5
8.3
5.4-19.8
Rivers and
lakes
2.0
290
4.3
n.a.
3.0
23.6
11.3-62.9
Weighted
means (or
total)
(363.8)
126
0.26
0.07
2.8
8.0
6.3-14.4
Herbivore
Carnivore
Microbivore Saprotroph
Invertebrates
40%
80%
30%
20%
Vertebrates
50%
80%
--
--

Group
P /A %
1 Insectivores
0.86
2 Birds
1.29
1.51
4 Other Mammals
3.14
9.77
25.0
40.7
8 Herbivores
20.8
9 Carnivores
27.6
10 Detritivores
36.2
Non-social insects
11 Herbivores
38.8
12 Detritivores
47.0
13 Carnivores
55.6
Krebs Fig 26.4
118 Secondary Production

Table 6.1 A simple taxonomic-trpohic categorization of heterographic organisms. For each category
the characteristic assimiliation (A/C) and growth (P/A) efficiencies are given. (From Heal and Maclean,
1975.)
Trophic Function
Herbivore
Carnivore
Microbivore
Saprotoroph
A/C
P/A
A/C
P/A
A/C
P/A
A/C
P/A
Micro
organi
sms
0.40
Inverti
brates
0.40
0.40
0.80
0.30
0.30
0.40
0.20
0.40
Vetebr
ate
homot
herms
0.50
0.02
0.80
0.02
Vetebr
ate
heterot
herms
0.50
0.10
0.80
0.10
0.30
Proportion
0.25
0.20
0.15
0.10
0.05
0.00
0
4
6
Food chain length
10
Georges Bank Cod Summary
Georges Bank
240 x 120 km in size
Primary productivity 0.9 kg C / m^2 / year

Cod range from trophic level 4 - 6
Transfer efficiencies ~ 10% between trophic levels
What is a guess at sustainable harvest?
Digression - Confidence Limits and
Sensitivity Analysis
What if energy transfer was 8% instead of 10%?

What if less of Georges Bank was suitable habitat?
What about other species of bottom fish?

Ecological calculations are almost worthless without some
measure of the confidence boundaries. Often confidence is
assessed through sensitivity analysis - how much difference
would mistakes in the input values make to the final result?
Columbus and Cabot
In 1492, Columbus sailed the ocean blue.
In 1497 John Cabot discovers Cape Cod and the Basque fishing
vessels
In 1500s there is a cod rush to Massachusetts up to Newfoundland
In 1930s, factory trawlers arrive.
In 1960s, U.S. and Canada increase fishing effort
In 1990s
NOAA Pub CRD0204
How could catch be at 50,000 tons for years?
Productivity
Biomass
(Standing Stock)
What happens to system when cod
are removed?
Trophic cascades
Brooks, J. L. and S. I. Dodson, 1965. Predation, body

size, and composition of plankton. Science 150:
28-35
Keystone Species
Paine, R. T., 1966. Food web complexity and species

diversity. The American Naturalist 100: 65 - 75.
Question: What controls the diversity of and
relative abundance of different species in the
intertidal community?
First careful observations of the community

Transplant different species and find which ones are
competitively dominant (dominance hierarchy)
Construct food web for predatory species
What will happen if one of the species is removed?
The answer
is in your next EcoBeaker lab
Wrap-up
Ecology can make some general predictions about what

might happen to Georges Bank system.
Ecology can also make some predictions about whether and
how long it might take cod populations to recover.
More on the first topic at the end of the course, when
discussing communities.
More on the second topic in a couple weeks, when talking
about population growth.
1.018/7.30J
Fall 2003
Lecture 8 Introduction to Biogeochemical Cycles

Krebs. Chapter 27. Ecosystem Metabolism III: Nutrient Cycles
Ramanujan K. 2003. Ocean plant life slows down and absorbs less carbon. (H, W)
http://www.eurekalert.org/pub_releases/2003-09/nsfc-op1091603.php. accessed 9/16/03
Rietschel M. 2003. Analysis pours cold water on flood theory. Nature. 425:111. (H,W)
Outline for today:

I. Discussion of pre-proposals
II. Biogeochemistry
a. Dinosaur question
b. Reservoirs and residence times
c. Example: methane
III. Guest speaker: Anna Mehrotra
Study questions:
What are the major compartments that we consider when drawing biogeochemical cycles? What
are some of the major sub-compartments that we also consider?
Explain what two factors contribute to a compound having a long residence time in an ocean or in
the atmosphere.
What are some major differences between the global biogeochemical cycles for P vs C, or CO2 vs.
CH4?
Wetland, rice patties, termites and cows are major sources of CH4. Why?
More of a brain teaser than study question (Hint: think about residence times and fluxes, see
water cycle Krebs Figure 28.7)
1.018/7.30J
Fall 2003
Lecture 6 Introduction to Secondary Productivity

Krebs. Chapter 23 pages 463-469. Food Chains and Trophic Levels
Guterl, F. 2003. Troubled seas: Ninety percent of the big fish have already been caught.
Newsweek. July 14 edition, p 46. (H,W)
Pauly D and V Christensen. 1995. Primary production required to sustain global fisheries.
Nature. 374:213-4. (H,W)
REMINDER:
Pre-proposal due Thursday!
No late proposals!
MOVIE NIGHT:
Re-showing of Cane Toads
Thursday, 8pm
Food provided
The last few lectures, we have focused on primary productivity. As we saw previously, autotrophs are
able to capture 1-2% of the incoming solar radiation.
We are now going to explore what happens to the energy stored in autotrophic biomass. Secondary
productivity is defined as the rate of biomass accumulation by heterotrophs (herbivores, carnivores
and detritivores).
For trophic level n:

Rn
An
In
Pn
Pn-1
Fn
NU =
not used
biomass
biomass
Pn-1 = Productivity at trophic level n-1

NU = Productivity from trophic level n-1
not used by trophic level n
= Amount of energy ingested
Fn
= Amount of energy lost as fecal matter

(but available to detritivores)
An
Dead organic matter

compartment of
decomposer system
In
= Amount of energy assimilated

(i.e. available for metabolism)
Rn
= Amount of energy lost to respiration
Pn
= Productivity of trophic level n

(evident as growth and reproduction)
Study questions
1. What is the real truth to Dogberts insights? What is the wasted step?
2. Define a trophic level. What are the difficulties in assigning a species to a single trophic level?
3. Describe the difference between exploitation, assimilation and production efficiencies. What are the typical
ranges of each of these efficiencies? How do they combine to give an overall ecological efficiency?
4. According to the Newsweek article, what are the consequences throughout the marine food web of
overfishing of top predator fish?
5. According to Pauly and Christensens article, how much of aquatic primary productivity is required for the
amount of fish caught annually? How does this number differ between freshwater and marine systems?
Why does it seem unlikely that humans will be able to harvest much more of the worlds aquatic productivity
than is already being harvested?
N : P
20 : 1
Correlation between the concentration of nitrate and phosphate in

waters of the Atlantic, Indian, and Pacific Oceans
C : N
7: 1
Western Atlantic
Units:
[CO3]=10-2 millimols per liter
Western Atlantic
Deep
Water
Samples
O2 : N
6: 1
Units:
REDFIELD HYPOTHESIZED:
The proportions of elements in the
atmosphere and the sea are controlled by the
biogeochemical cycle
NO3 + PO4 + O2
CO2 + PO4 + NO3
Living Organisms + O2
Dead Organisms + O2
Deep
Sea
If the elemental composition of the deep ocean water is dictated by the

composition of the plant material, the elements should vary in constant
proportion from place to place.
100% Saturation
O2
1) O2 between surface and

Mixed
minimum is `the amount
Layer
used to oxidize the
organic compounds as
they settle out of the
euphotic zone
O2 Minimum
Depth
2) Measured N:P:C ratios in

mid-ocean, surface and deep
ocean at various times
PO4
NO3
Adapted from
Krebs Fig. 23.3
Adapted from: Odum (1972)
From Smith
and Smith
2001

Herbivore
Carnivore
Microbivore
Saprotroph
Invertebrates
40%
80%
30%
20%
Vertebrates
50%
80%
--
--
Microbivore = an organism that feeds on microorganisms

Saprotroph = a fungus that feeds on detritus

Group
P /A %
1 Insectivores
0.86
2 Birds
1.29
1.51
4 Other Mammals
3.14
9.77
25.0
40.7
8 Herbivores
20.8
9 Carnivores
27.6
10 Detritivores
36.2
Non-social insects
11 Herbivores
38.8
12 Detritivores
47.0
13 Carnivores
55.6
Cod
Bottom-dweller but stays relatively close to the surface (within

a few hundred meters).
Can reach up to 200 pounds and live 20 - 30 years
Large females can lay 10 million eggs / year

Eats anything that moves and is smaller than mouth
Cod Fishing
When Columbus sailed, 1000 Basque ships were fishing

Georges Bank and Newfoundland.
If 1/2 of these were in Georges Bank and each ship pulled
in 20 tons of cod, catch was about 10,000 tons / year.
By mid 1500s, 60% of fish eaten in Europe were cod.
Recipe book of Charles V in France
Salt cod is eaten with mustard sauce or with melted

fresh butter over it.
- Guillaume Tirel, Le Viandier, 1375
Cokkes of Kellyng
Take cokkes of kellyng; cut hem smalle. Do hit yn a
brothe of fresch fysch or of fresh salmon; bowle hem
well. Put to myllke and draw a lyour of bredde to hem
with saundres, safferyn & sugure and poudyr of pepyr.
Serve hit forth, & otheyr fysch amonge: turbut, pyke,
saumon, chopped & hewn. Sesyn hem with venyger &
salt.
-anonymous manuscript from fifteenth century
How Much Cod Can Be Caught?
From Pauly and Christensen

See text 546-547
TABLE 2 Global estimates of primary production (PP), of PPR to sustain world fisheries (mean for 1988-1991,
net weight), and of the mean trophic levels (TL) of the catches, by ecosystem type
PPR (catches +discards)
Ecosystem
type
Area
(106 km2)
PP
(gC m-2 yr-1)
Catch
(g m-2 yr-1)
Discards
(g m-2 yr-1)
TL of the
catch
Mean
(%)
95%
Confidence
interval
Open ocean
332.0
103
0.01
0.002
4.0
1.8
1.3-2.7
Upwellings
0.8
973
22.2
3.36
2.8
25.1
17.8-47.9
Tropical
Shelves
8.6
310
2.2
0.671
3.3
24.2
16.1-48.8
Nontropical
shelves
18.4
310
1.6
0.706
3.5
35.3
19.2-85.5
Coastal/reef
systems
2.0
890
8.0
2.51
2.5
8.3
5.4-19.8
Rivers and
lakes
2.0
290
4.3
n.a.
3.0
23.6
11.3-62.9
Weighted
means (or
total)
(363.8)
126
0.26
0.07
2.8
8.0
6.3-14.4
Herbivore
Carnivore
Microbivore Saprotroph
Invertebrates
40%
80%
30%
20%
Vertebrates
50%
80%
--
--

Group
P /A %
1 Insectivores
0.86
2 Birds
1.29
1.51
4 Other Mammals
3.14
9.77
25.0
40.7
8 Herbivores
20.8
9 Carnivores
27.6
10 Detritivores
36.2
Non-social insects
11 Herbivores
38.8
12 Detritivores
47.0
13 Carnivores
55.6
Krebs Fig 26.4
118 Secondary Production

Table 6.1 A simple taxonomic-trpohic categorization of heterographic organisms. For each category
the characteristic assimiliation (A/C) and growth (P/A) efficiencies are given. (From Heal and Maclean,
1975.)
Trophic Function
Herbivore
Carnivore
Microbivore
Saprotoroph
A/C
P/A
A/C
P/A
A/C
P/A
A/C
P/A
Micro
organi
sms
0.40
Inverti
brates
0.40
0.40
0.80
0.30
0.30
0.40
0.20
0.40
Vetebr
ate
homot
herms
0.50
0.02
0.80
0.02
Vetebr
ate
heterot
herms
0.50
0.10
0.80
0.10
0.30
Proportion
0.25
0.20
0.15
0.10
0.05
0.00
0
4
6
Food chain length
10
Georges Bank Cod Summary
Georges Bank
240 x 120 km in size
Primary productivity 0.9 kg C / m^2 / year

Cod range from trophic level 4 - 6
Transfer efficiencies ~ 10% between trophic levels
What is a guess at sustainable harvest?
Digression - Confidence Limits and
What if energy transfer was 8% instead of 10%?

What if less of Georges Bank was suitable habitat?
What about other species of bottom fish?

Ecological calculations are almost worthless without some
measure of the confidence boundaries. Often confidence is
assessed through sensitivity analysis - how much difference
would mistakes in the input values make to the final result?
Columbus and Cabot
In 1492, Columbus sailed the ocean blue.
In 1497 John Cabot discovers Cape Cod and the Basque fishing
vessels
In 1500s there is a cod rush to Massachusetts up to Newfoundland
In 1930s, factory trawlers arrive.
In 1960s, U.S. and Canada increase fishing effort
In 1990s
NOAA Pub CRD0204
How could catch be at 50,000 tons for years?
Productivity
Biomass
(Standing Stock)
What happens to system when cod
are removed?
Trophic cascades
Brooks, J. L. and S. I. Dodson, 1965. Predation, body

size, and composition of plankton. Science 150:
28-35
Keystone Species
Paine, R. T., 1966. Food web complexity and species

diversity. The American Naturalist 100: 65 - 75.
Question: What controls the diversity of and
relative abundance of different species in the
intertidal community?
First careful observations of the community

Transplant different species and find which ones are
competitively dominant (dominance hierarchy)
Construct food web for predatory species
What will happen if one of the species is removed?
The answer
is in your next EcoBeaker lab
Wrap-up
Ecology can make some general predictions about what

might happen to Georges Bank system.
Ecology can also make some predictions about whether and
how long it might take cod populations to recover.
More on the first topic at the end of the course, when
discussing communities.
More on the second topic in a couple weeks, when talking
about population growth.
1.018/7.30J
Fall 2003
Lecture 8 Introduction to Biogeochemical Cycles

Krebs. Chapter 27. Ecosystem Metabolism III: Nutrient Cycles
Ramanujan K. 2003. Ocean plant life slows down and absorbs less carbon. (H, W)
http://www.eurekalert.org/pub_releases/2003-09/nsfc-op1091603.php. accessed 9/16/03
Rietschel M. 2003. Analysis pours cold water on flood theory. Nature. 425:111. (H,W)
Outline for today:

I. Discussion of pre-proposals
II. Biogeochemistry
a. Dinosaur question
b. Reservoirs and residence times
c. Example: methane
III. Guest speaker: Anna Mehrotra
Study questions:
What are the major compartments that we consider when drawing biogeochemical cycles? What
are some of the major sub-compartments that we also consider?
Explain what two factors contribute to a compound having a long residence time in an ocean or in
the atmosphere.
What are some major differences between the global biogeochemical cycles for P vs C, or CO2 vs.
CH4?
Wetland, rice patties, termites and cows are major sources of CH4. Why?
More of a brain teaser than study question (Hint: think about residence times and fluxes, see
water cycle Krebs Figure 28.7)
How would a C atom

from a dinosaur
end up in your sandwich?
Global Nutrient Cycling
Precipitation
Uptake
Bioelements
in solution
H20
(+ volatile
Bioelements)
Volatile
bioelements only
Terrestrial
food web
Decomposition
Volatile
bioelements only
Evaporation
Death
Dead organic
matter
OCEAN
Marine
food web
Weathering
Losses by water runoff

Terrestrial biosphere
Dead organic
matter
Sinking
Adapted from Krebs,

2001. Figure 27.1
Reservoir: How much of a substance is

present in one of these compartments
Atmosphere
Land
Fresh
water
Oceans
Sediments
Rocks
100
0.001
Mesopause
80
MESOSPHERE
Height (km)
60
Stratopause
40
STRATOSPHERE
20
100
Tropopause
TROPOSPHERE
0
-100
-80
-60
1000
-40
-20
20
40
Temperature (oC)
Adapted from http://www.met-office.gov.uk/research/stratosphere/
Pressure (hPa)
0.01
Global Methane Cycle

(units of
1012
g CH4/yr)
Sources
535
Sinks
515
(Natural 160 + Anthropogenic 375)
stratosphere
40
445
Reaction with OH
CH4
100
fossil fuel
(mining,
burning)
troposphere
85
30
cows
landfills +
other waste
treatment
Data from Schlesinger, 1997
115
30
10
90
termites
oceans
wetlands
Estimated Sources and Sinks of Methane in the Atmosphere

12
in Units of 10 g CH4 /yra
Sources
Range
Likely
Natural
Wetlands
Tropics
Northern latitude
Others
Termites
Ocean
Fres hwater
Geological
Total
30 20 510 515-
80
60
15
50
50
25
15
65
40
10
20
10
5
10
160
45
50
30
30
30
40
15
15
20 - 70
20 - 30
15 - 80
65 -100
20 - 80
20 -100
40
25
25
85
40
60
375
Anthropogenic
Fossil fuel related
Coal mines
Natural gas
Petroleum industry
Coal combustion
Waste management system
Landfills
Animal waste
Domestic sewage treatment
Enteric fermentation
Biomass burning
Rice paddies
Total
15 25 55-
Total sources
Sinks
Reaction with OH
Removal in stratosphere
Removal by soils
535
330 -560
25 - 55
15 - 45
Total sinks
Atmospheric increase
445
40
30
515
30 - 35
30
What is the probability

that a water molecule
from Napoleons urine
is in your water bottle?
Pools (km3)
The Global Water Cycle
Fluxes (km3/yr)
Atmosphere
13,000
Net transport to
land
11,000
71,000
40,000
Ice
33,000,000
River flow
40,000
Soil Waters
122,000
Groundwater
15,300,000
Reference: Schlesinger, 1997
385,000
425,000
Oceans
1,350,000,000
1.018/7.30J
Fall 2003
Lecture 9 Nitrogen and Phosphorus Cycling

Outline for today:
I. Review of Biogeochemical cycling mechanics and Mass balance
a. Reservoirs and Fluxes
b. Sources and sinks
II. Nitrogen
a. Role in biology
b. Reservoirs
c. Nitrogen Sources
d. Nitrogen Sinks
III. Phosphorus
a. Role in biology
b. Reservoirs
c. Phosphorus Sources
d. Phosphorus Sinks
Study questions:
Why is nitrogen fixation only carried out by prokaryotes? Why didnt humans and plants evolve a
way to fix nitrogen from the atmosphere directly?
Would nutrients have a longer residence time in deciduous or coniferous forests? Why?
In todays Nitrogen cycle is nitrogen fixation balanced by denitrification?
I. Review of Biogeochemical cycling mechanics and Mass balance

a. Reservoirs and Fluxes, Sources and sinks
Inputs > outputs (sink) Inputs < outputs (source)
Mass balace: Inputs - Outputs + Sources - Sinks = Mass
Steady state: Mass =0
II. Nitrogen Atomic # 7 14.0067 g mol 1
a. Role in biology
B.P. 195.8C
N is an essential component of proteins, nucleic acids and other cellular constituents.
b. Reservoirs 79% of the atmosphere is N2 gas. The N=N triple bond is relatively
difficult to break ,requires special conditions. As a result most ecosystems are N-limited. N2
dissolves in water, cycles through air, water and living tissue.
c. Nitrogen Fixation
Abiotic: lightning (very high T and P) 107 metric tons yr-1 ~ 5-8% of total annual N
fixation. (weathering of rocks is an insignificant source)
Biotic: Nitrogen fixation by microbes, (prokaryotic bacteria) typically either freeliving azobacter or rhizobium living symbiotically with plants (such as legumes). Total N
fixed by biological processes is approx. 1.75 x108 metric tons yr-1
Biological mechanism of nitrogen fixation: uses an enzyme complex called nitrogenase consisting of two
proteins an iron protein and a molybdenum-iron protein.
N2+ 8H+ + 8e -+ 16 ATP = 2NH3+ H2+ 16ADP + 16 Pi

oxidised ferredoxin
reduced ferredoxin
oxidised Fe protein
reduced Fe protein
4 ATP
2e-
4 AFP
reduced Mo Fe protein
oxidised Mo Fe protein
2e-
HN=NH
2 H+
N2
H2N=NH2
HN=NH
2NH3
H2N=NH2
Adapted from http://helios.bto.ed.ac.uk/bto/microbes/nitrogen.htm#Top
The Fe protein gets reduced by electrons donated by ferredoxin. Then the reduced Fe protein binds ATP and
reduces the molybdenum-iron protein, which donates electrons to N2, producing HN=NH. In two further cycles of
this process (each requiring electrons donated by ferredoxin) HN=NH is reduced to H2N-NH2, and this in turn is
reduced to 2NH3.
ferredoxin is generated by either photosynthesis, respiration or fermentation, depending on the

type of organism
nitrogenase is inhibited in the presence of oxygen. N-fixing prokaryotes operate either
anaerobically (Clostridium, Desulfovibrio, Purple sulfphur Bacteria) or develop special mechanisms such as
extremely high respiratory rates (Azobacter) and/or cellular features to limit oxygen diffusion, or else
develop symbiotic relationships (Rhizobium) where the host plant scavenges oxygen. Cyanobacteria,
protect nitrogenase in special heterocysts which possess only PS I.
Industrial: The Haber-Bosch process (1909) high P and relatively high T, uses
Iron as a catalyst to convert N2 to ammonia (usually further processed to urea and
ammonium nitrate (NH4NO3) still the cheapest means of industrial N fixation. 5x107
metric tons yr-1
Combustion Side Effect: High T and P oxidizes N2 to Nox 2x107 metric tons yr-1
Since 1940s amount of N available for uptake has more than doubled.
Anthropogenic N
inputs are now equal to biological fixation.

d. Nitrogen Cycling
plants directly take up NH4+ or NO3Nitrification by chemoautotrophs

Bacteria of the genus Nitrosomonas oxidize NH3 to NO2Baceria of the genus Nitrobacter oxidize the nitrites to NO3Denitrication
Anaerobic respiration of NO3- to dinitrogen gas by several specis of Psuedomonas,
Alkaligenes, and Bacillus
Sources of anthropogenic N loads: Fertilizers, Legume Crops, Atm Deposition, Sewage,
Deforestation, Draining of wetlands
Trends in Fertilizer Use
(million metric tons

160
140
120
100
80
60
40
20
0
1960 1965
1970
1975
AFRIC
ASIA
EUROPE
NORTH AMERICA
1980
1985
1990
1995
OCEANIA
SOUTH AND CENTRAL AMERICA
WORLD
Adapted from the Food and Agriculture Organization of the United Nations (FAO), FAOSTAT Statistical Database (FAO,
Rome, 1997).
Fate of N? In most terrestrial and freshwater ecosystems N is a limiting nutrient, gets cycled
efficiently. What happens when plants have enough N (i.e. greater 16:1 N:P ratio)?
Flushing/erosion dissolved and particulate matter in streamwater, (DIN, DON, TN, Org N)
leaching to groundwater NO3- is an anion, does not sorb well to clays, highly water soluble. When N
saturation of ecosystem occurs, excess N tends to leave the system in the form of nitrate.
, VOCs, denitrification, burning, emigration, harvesting
Effects of Increased N loading:
Eutrophication in aquatic systems, coastal algal blooms and Dead Zone, fish kills, increased
turbidity, selective pressures in terrestrial systems favoring species-poor grasslands and
forests
Nitrate MCL 10mg L-1
Nitric oxide precursor of acid rain and smog
Nitrous oxide long lived greenhouse gas that can trap 200 times as much heat as CO2
III. Phosphorus Atomic # 15 30.97 g mol 1
B.P. 280C
P is very reactive, does not exist in pure elemental form. In contact with air, it forms phosphate PO43-.
In water, phosphates are protonated to form HPO42-, H2PO4- and H3PO4.
PO43- orthophosphate, the most simple molecular form of phosphate, aqueous form under very basic
or alkaline conditions
HPO42- : aqueous form under basic or alkaline conditions
H2PO4- : aqueous form under neutral conditions
H3PO4 : aqueous form under very acidic conditions
a. Role in biology
Phosphorus is an essential nutrient for plants and animals in the form of ions PO43- and HPO42- . It is found in
DNA-molecules (it binds deoxyribose sugars together forming the backbone of the DNA molecule), ATP and
ADP, and lipid cell membranes (phospholipids). P is also a fundemental to tissues such as bones and teeth.
b. Reservoirs Unlike C, N and other important bioelements P does not exist in a

gaseous state at typical environmental Temps and Pressures. Cycles through
water (DOP and DIP), soils and sediments (adsorption to mineral surfaces) and
organic tissue/humic material.
c. Phosphorus Sources Found in sedimentary rocks such as apatite

(Cax(OH)y(PO4)z), fossilized bone or guano. Weathering from phosphate rocks
found in terrestrial rock formations and some ocean sediments (PO4 is soluble
in H2O). Guano (excrement of fish-eating birds) mining for fertilizers and
sewage. Detergents have historically contained Na3PO4, though newer types
are avoiding it.
d. Phosphorus Sinks uptake of orthophosphate by plants through the roots,
incorporation into plant tissue and heterotroph tissues, decomposition returns P
to water and soils via microbial mineralization; eventually it is washed out to the
oceans, sinks to the floor (becomes limestone) and is not recycled for millions
of years.
Adapted from: http://www.starsandseas.com/SAS%20Ecology/SAS%20chemcycles/cycle_phosphorus.htm
1.018/7.30J
Fall 2003
Lecture 10 Sulfur Cycles

Krebs Chapter 28 pages 590-607
READINGS FOR NEXT THURSDAYS LECTURE:

Global climate change articles (handed out separately)
Outline for today:

I. Quizzes
II. Global climate change discussion next Thursday
III. Sulfur
A. Reservoirs and residence times
B. Biology of sulfur
C. Global S cycle
D. Human Impacts
E. Isotope analyses
III. Sulfur
A. Reservoirs and residence times
Size (1012 g)
Flux (1012 g/yr)
MRT (yr)
270
__________
Seawater
1.3 x 109
310
_________
__________
Sedimentary
Rocks
7.4 x 109
220
__________
Land Plants
8500
24
__________
Soil Organic
Matter
16000
72
__________
Reservoir
Atmosphere
Will S be well-mixed in the atmosphere?
B. Biology of sulfur
reduced
oxidized
assimilation
org S
mineralization (decomposition)
SO42-
S0
requires energy
releases energy
H2S
C. Global cycle
Adapted from Smith,200. Elements of Ecology.
The Global Sulfur Cycle

Wet and dry
deposition
90
Fluxes (1012 g S/yr)
Transport to sea
5
8
20
90
Transport to land
4
4
Dust
Biogenic
gases
130
Human mining
and extraction
150
180
Deposit
ion
Rivers
144
Sea
salt
16
Biogenic
gases
Natural weathering
and erosion
72
Pyrite
39
D. Human impacts
Global SO2 Emissions
Hydrothermal
sulfides 96
Adapted from Charlson et al. 1992 Science 255:423

E. Isotope analyses
34S = 1000 * [(34S/32S)sample (34S/32S)standard] / (34S/32S)standard
in
Smelters, Refineries, Automobiles?

S34 = +1.5
S34 = +3.1
S34 =+16
S34
=+1
S34 =+5.3
H2S
Great Salt
Lake
Copper
Smelters
Refineries
Autos
Anaerobic bacteria
S34 = +1.5
Mean Values
S34 = +3.1
Smelters Strike
S34 = +5.3
(expected +9)
Mean Values
S34 = +6.4
(expected +16)
Study questions:
Name the major ways in which the sulfur cycle resembles and does not resemble the nitrogen and
phosphorus cycles.
What are major anthropogenic and non-anthropogenic sources of S emissions into the
atmosphere?
How does acid rain form? How does acid mine drainage form?
Explain how sulfate reducing bacteria indirectly create SO2 emissions.
Explain how isotope ratios can be used to determine the relative contributions of different sources.
1.018/7.30J
Fall 2003
Lecture 11 Carbon Cycle

Global climate change articles (handed out last class)
Whitehouse D. 2003. Photosynthesis puzzle solved. BBC.
http://news.bbc.co.uk/2/hi/science/nature/3174582.stm. accessed 10/10/03
Bentley M. 2003. Synthetic trees could purify air. BBC.
http://news.bbc.co.uk/2/hi/science/nature/2784227.stm. accessed 10/10/03
Outline for today:

I. Finish S cycle / Stable Isotope Analyses
II. Global Carbon Cycle
A. C in the news
B. Global cycle
C. Carbon and temperature
D. Ecological effects of increasing CO2
The Global Carbon Cycle

fossil fuel
burning
GPP
Land
plants
560
Rp
Atmospheric Pool
750
120
+3.2/yr
60
60
0.9
92
Soils
1500
Net destruction
of vegetation
Pools (10 15 g C)
Fluxes (10 15 g C/yr)
Fossil Fuels
4000
Ocean
38,000
Rocks
81,000,000
90
Rivers
0.8
Burial
0.1
Measured changes in CO2 dissolved on the surface of the Atlantic ocean.
Adapted from: Schlesinger, 1997 (Figure 9.10)
Adapted from Krebs, Fig. 28.13
Adapted from Krebs, Fig. 28.11

Trees from Arizon, North Carolina and Italy
Concentration of CO2 at Mauna Loa Observatory

In Hawaii. Adapted from Krebs Fig 28.9.
Long-term variation in global temperature

and atmospheric CO2 concentration
determined from the Vostok Ice Core,
Antarctica. Adapted from Krebs. Fig. 28.15
Temperatures Relative to Millenial Average*. Adapted from Mann et.al., 1999
Its not just CO2

Atmospheric
Concentration
(ppm)
Annual
Concentration
Increase
(%)
Relative
greenhouse
efficiency
(CO2 = 1)
Current
Greenhouse
Contribution
(%)
Carbon
dioxide
351
0.4
57
CFCs
0.00225
15 000
25
Foams,
aerosols,
solvents,
refrigeration
Methane
1.675
25
12
Wetlands,
rice,
livestock,
fossil fuels
Nitrous
oxide
0.31
0.2
230
Fuels,
fertilizer,
deforestation
Gas
Principal
sources of
gas
Fossil fuels,
deforestation
Source: Schlesinger, 1997
Effects of increased CO2 on Phytoplankton:

Riebesell U., et. al. Reduced calcification of
Marine phytoplankton in response to increased
Atmospheric CO2. Nature 407:364 (2000).
Time variation of Larval weight

(adapted from Krebs Fig. 28.17)
Read:
AGNIESZKA BISKUP, GET THE OCEANS SOME TUMS
Published on October 7, 2003, Boston Globe, Page C2 Col 2
Study questions
What are the largest C reservoirs and fluxes in the environment?

What do we mean by the missing carbon? Where is this missing carbon likely to be?
How do temperate forests respond to elevated CO2 after 1-5 years? 30 years?
How can stable isotopes be used to determine temperature 1000s of years ago?
By what mechanism do oceans primarily absorb CO2?
1.018/7.30J
Fall 2003
Global Climate Change Discussion 10/16/03

The dramatic increase in atmospheric CO2 concentrations is alarming to many people. While
reduction in emissions is the obvious solution, some people are proposing more immediate actions to
reduce the amount of CO2 in the atmosphere. Some proposed ideas are iron-fertilization, deep-sea
injection of CO2 and carbon sequestration in terrestrial plants. There is also a lot of debate about
whether increasing CO2 concentrations will lead to greater terrestrial and aquatic productivity, which
could serve as a feedback mechanism to absorb some of the extra atmospheric CO2.
Were going to spend a lecture evaluating these topics. To make the discussion more informative, Ive
assigned some readings pertinent to each topic. Each person is responsible for reading one set of
articles. You should be prepared to talk about the answers to the questions below, drawing on the
major points of the below articles and any other information you find (these articles were some that I
found briefly searching through Nature & Science).
When you get to class, you will break into groups, share your answers to the questions, and prepare
to explain your topic to the class.
As you read these articles, keep the following questions in mind:
What is the rationale behind each approach? How will this approach work to reduce
atmospheric CO2?
In which compartment of the environment will the C be stored? What is the MRT?
Can it work in the short-run? In the long-run?
What are other effects besides decreasing atmospheric CO2?
What are the major uncertainties?
Overall, do you think its a good idea? Would your answer be different if you lived in Holland
or on a tiny island barely above sea level?
Everyone (focus on pages 422-426A)
Betts KS. 2000. Engineering maintainable development. Environmental Science and Technology.
34:422A.
1. Ecological responses to high CO2 concentrations (Adrienne, April, Ayse, Ben, Candace, Cynthia)
Norby R. 1997. Inside the black box. Nature. 388:522.
Sarmiento J. 2000. That sinking feeling. Nature. 408:155.
Schlesinger WH and JH Lichter. 2001. Limited carbon storage in soil and litter of experimental forest
plots under increased atmospheric CO2. Nature. 411:466.
DeLucia EH. 1999. Net primary productivity of a forest ecosystem with experimental CO2
enrichment. Science. 284:1177.
Gill RA et al. 2002. Nonlinear grassland responses to past and future atmospheric CO2. Nature.
417:279.
2. Deep-Sea or Mineral Injection of CO2 (Genevieve, Helen, Jason, Jennifer, Jessie, Jonathon, Katie)
Dalton R. 1999. US warms to carbon sequestration research. Nature. 401:315.
Kaiser J. 1998. A way to make CO2 go away: Deep-six it. Science. 281:505.
Seibel BA and PJ Walsh. 2001. Potential impacts of CO2 injection on deep-sea biota. Science.
294:319.
Celia MA. 2001. How hydrogeology can save the world. Ground Water.
Caldeira K and ME Wickett. 2003. Anthropogenic carbon and ocean pH. Nature. 425:365.
Lackner KS. 2003. A guide to CO2 sequestration. Science. 300:1677.
3. C sequestration in terrestrial systems (Kelly, Ling, Liz, Lynn, Marion, Maywa, Melissa)
Smaglik P. 2000. United States backs soil strategy in fight against global warming. Nature. 406:549.
Krner C. 2003. Slow in, rapid out carbon flux studies and Kyoto targets. Science. 300:1242.
Goodale CL and EA Davidson. 2002. Uncertain sinks in the shrubs. Nature. 418:593.
Betts RA. 2000. Offset of the potential carbon sink from boreal forestation by decreases in surface
albedo. Nature. 408:187.
Fang J et al. 2001. Changes in forest biomass carbon storage in China between 1949 and 1998.
Science. 292:2320.
4. Iron Fertilization of Open Oceans (Michael, Nicole, Nina, Priya, Schuyler, Tom)
Buesseler KO and PW Boyd. 2003. Will ocean fertilization work? Science. 300:67.
Chisholm SW, PG Falkowski, and JJ Cullen. 2001. Dis-crediting ocean fertilization. Science.
294:309.
Watson AJ et al. 2000. Effect of iron supply on Southern Ocean CO2 uptake and implications for
glacial atmospheric CO2. Nature. 407:730.
Lawrence MG. 2002. Side effect of oceanic iron fertilization. Science. 297:1993.
Lam PJ and SW Chisholm. 2002. Iron fertilization of the oceans: Reconciling commercial claims
with published models. http://web.mit.edu/chisholm/www/Fefert.pdf. accessed 10/8/03.
Ecology
Populations
Communities
Ecosystems
Population Ecology
How do populations grow?
Most widely used branch of ecology
Endangered species
Invasive species
Agricultural Pests
Disease dynamics
Major Problem: People vs. Elephants

Park is too small for the elephants.
People are settling outside the park
Elephants like farm food
Elephants and cows both need water
Task: Make a model of elephant population dynamics

to ask what-if questions about purchasing more land.
w/ Sandy Andelman
Data from (2001) Moss, CJ. J Zool. 255: 145-156
How will the elephant population grow?

dN/dt = B - D + I - E
B = Births
D = Deaths
I = Immigration
E = Emigration
Continuous Exponential Growth

Births = bNt
Deaths = dNt
Ignore I and E
for now
dN/dt = bNt - dNt

= (b - d) Nt
= r Nt
Integrate to get Nt =
r = Intrinsic rate of growth
Discrete Exponential Growth

Nt = Nt-1 + bNt-1 - dNt-1 + I - E
Ignoring I and E, we get
Nt = (b - d) Nt-1
= r Nt - 1
Try this equation in a spreadsheet.
Density Dependence
Nt = rNt-1 (1 - N / K)
Logistic Growth Equation
K = Carrying capacity
Try r of different values and graph
Digression: Chaos
Digression: Growth rate vs. Population Size
This graph is the basis of population management and

harvesting. For instance, the cod fishery might be
managed using a graph like this.
Measuring this turns out to be very hard
Age at First Reproduction

Nt = bNt-a - dNt-1
Cumulative proportion
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
8 10 12 14 16 18 20 22
Age at first known birth

Probability of first birth occurring at each
age for known-age females.
Try changing these and see how it affects doubling time
Digression: Why wait to reproduce?

Obviously, you will have more offspring faster if you
reproduce sooner. Why doesnt everything reproduce
as soon as its born?
R-selected species: reproduce very at young

age and small size / resources.
K-selected species: reproduce at older age and
larger size / resources
Environmental Stochasticity
Demographic Stochasticity
What happens when population is small?
Small numbers means that probability comes
into play.
Allee effect
When population is small, some things may
get harder (like finding mates)
If so, fecundity could actually decrease at
low population size.
Some Terms
Intrinsic rate of growth: maximum offspring / individual / time
Doubling time: Amount of time for population to double
Carrying capacity: The maximum population that the
environment can sustain
Discrete vs. continuous: Do events happen continuously or
once per some unit of time (such as once per year).
Density-dependent/ independent: Are the parameters like b and
d dependent on the density of the population
Demographic stochasticity: When populations are low enough,
chance events matter to the population size.
Alee effect: Fecundity decreasing at low population size
Recap
Basic Population Dynamics Eqn
dN/dt = B - D + I - E
Continuous Exponential growth
dN/dt = rN
Discrete Exponential growth
N(t) = N(t-1) + rN(t-1)
Discrete Logistic growth
N(t) = N(t-1) + rN(t-1)[(K-N(t-1))/K]
Digression: Why wait to reproduce?

Obviously, you will have more offspring faster if you
reproduce sooner. Why doesnt everything reproduce
as soon as its born?
R-selected species: reproduce at young age and

small size or resources.
K-selected species: reproduce at older age and
larger size or resources
Demographic Stochasticity
What happens when population is small?
Small numbers means that probability comes
into play.
Allee effect
When population is small, some things may
get harder (like finding mates)
If so, fecundity could actually decrease at
low population size.
Estimating Population Size

With luck, you can count (like elephants)
Normally, you must sample. Sampling, and analyzing
samples, is 90% of most ecologists job.
Some sampling techniques
Estimating Model Parameters

1.
2.
3.
4.
5.
Plot data
Select a growth equation
Select parameters for that growth equation
Plot the equation over the data
Measure the distance of the equation plot from the data
points
6. Change the parameters and repeat
7. Select the parameters that give the best-fit to the data
8. You can repeat this with a different equation and see
which one fits better - if equations have different
numbers of parameters, must take into account that its
easier to fit data with more parameters.
Split Data Into Ages or Stages

birth rate
death rate
Juvenile
0.02
Adult
0.2
0.01
Ancient
0.05
0.05
N(juvenile, t) = 0.98 * N(juvenile, t-1)

+ 0.2 * N(adult, t-1) + 0.05 * N(ancient, t-1)
N(adult, t) = 0.99 * N(adult, t-1) + prop_age_14 * N(juvenile, t-1)
N(ancient, t) = 0.95 * N(ancient,t-1) + prop_age_55 * N(adult,t-1)
Life Tables
Just using matrices to organize data on birth and death
rates at different ages / stages.
N(juvenile, t) = 0.98 * N(juvenile, t-1)
+ 0.2 * N(adult, t-1) + 0.05 * N(ancient, t-1)
N(adult, t) = 0.99 * N(adult, t-1) + prop_age_14 * N(juvenile, t-1)
N(ancient, t) = 0.95 * N(ancient,t-1) + prop_age_55 * N(adult,t-1)
juv
adult =
Ancient
|0.91
|0.02
|0
0.2
0.99
0.06
0.05
0
0.95
|
| *
|
juv
adult
ancient
Life Tables are just Matrices

Eigenvector = Stable age distribution
Eigenvalue = Growth rate
In general, population dynamics is not useful for
making accurate quantitative predictions.
Its useful for making qualitative predictions comparing
different scenarios.
Individual-based Models
EcoBeaker-style
Follow individual creatures. Each creature can have its own
Variables
Pluses
Can have infinite stages, ages, etc.
Can account for space, interactions between individuals
Minuses
Often lots of parameters
Limits on number of creatures
Hard to make general conclusions
Some Terms
Intrinsic rate of growth: maximum offspring / individual / time
Doubling time: Amount of time for population to double
Carrying capacity: The maximum population that the
environment can sustain
Discrete vs. continuous: Do events happen continuously or
once per some unit of time (such as once per year).
Density-dependent/ independent: Are the parameters like b and
d dependent on the density of the population
Demographic stochasticity: When populations are low enough,
chance events matter to the population size.
Alee effect: Fecundity decreasing at low population size
Stable age/stage distribution - the eigenvector for the life table
matrix
1.018/7.30J
Fall 2003
Lecture 15 Human Population Growth

READINGS FOR NEXT LECTURE: (some of these are from last weeks lectures)
Krebs Chapter 28: Pages 583-590.
Krebs Chapter 9: Population Parameters
Krebs Chapter 10: Demographic Techniques: Vital Statistics
Krebs Chapter 11: Population Growth
Outline for today:

1. Historical population growth
2. Carrying capacity and ecological footprints
3. Life tables
4. Guest speaker: David Greene
Study Questions:
Describe the concept of carrying capacity. Why is it hard to define the carrying
capacity of a country?
Doubling times for human population have decreased significantly over the past 2000
years. What does this imply about the rate of growth? (Use an equation)
Define the concept of ecological footprint, and what is involved with calculating one.
Compare the ecological footprint of N. America and Asia.
Compare stable and expansive populations, and explain the idea of population
momentum.
How do life tables help you predict future population growth?
Life table
nx = number of individuals in age group
qx = mortality rate for individuals in age group
bx = number of babies born per person (or female) over time interval
1. Fill in boldly-outlined boxes.
2. Is this an expansive or stable population?

3. Which of the above numbers would change if:
(a) teenage pregnancy rates went down?
(b) all women delayed having births by 10 years?
(c) infant mortality rates increased?
(d) a new drug is introduced which lowers heart attacks in 40-49 year olds?
Age
group
1980 popn
(millions)
(nx)
Mortality
rate
(qx)
Birth rate
(bx)
0-9
215
0.005
167
0.009
132
0.015
119
0.027
0.05
40-49
86
0.042
50-59
55
0.054
...
..
..
..
..
0.3
30-39
..
0.1
20-29
2000
popn
(millions)
10-19
1990
popn
(millions)
in this case, bx is based on number born per person (not per female)
Human Population Growth
Krebs, 2001 (Figure 28.1)
Doubling times
Year (AD)
0
1650
1850
1930
1975
Population (billions)
0.25
1650 years
0.5
200 years
1.0
80 years
2.0
45 years
4.0
Population (millions)
Carrying capacity = 197 million
logistic curve
In 1924, Pearl and Reed fit U.S. population data for

1790-1910 using the logistic equation.
Joel E. Cohen, How Many People Can the Earth Support? Norton 1995
In 1990, the population of the U.S. was 250 million

Joel E. Cohen, How Many People Can the Earth Support? Norton 1995
Ecological Footprint
Ecological footprint by region, 1996

North America
Western Europe
Central and Eastern Europe
Middle East and Central Asia
Area units per person
12
Latin America & Caribbean

Asia / Pacific
Africa
10
OECD average
8
6
4
non-OECD average
2
0
299
484
343
384
307
3222
710
Adapted from: WWF, UNEP World Conservation Monitoring Centre, et al. 2000.
Living Planet Report 2000. Gland, Switzerland: WWF.
9 hectares / person
= 90,000 m2 / person
300 m
Manhattan has 1.5 million people

on 21.8 square miles
at 9 ha/person (1 ha=104 m2),

what is Manhattans ecological footprint?
Manhattans ecological footprint =

54,000 square miles
Estimates of Earths Carrying Capacity
Expansive population distribution
Source: www.wri.org
Stable population distribution
Source: www.wri.org
Adapted from: www.wri.org
Fertility Decline 1950 - 1998
Hypothetical Survivorship Curves
Source: Krebs, 2001(Figure 10.2)
Life Tables
Age
group
1980 popn
(millions)
(nx)
Mortality
rate
(qx)
Birth rate
(bx)
0-9
215
0.005
10-19
167
0.009
0.1
20-29
132
0.015
0.3
30-39
119
0.027
0.05
40-49
86
0.042
50-59
55
0.054
..
..
..
..
1990
popn
(millions)
2000
popn
(millions)
..
..
1.018/7.30J
Fall 2003
Lecture 16 Competition
READINGS:
Krebs Chapter 12: Species Interactions: Competition
Krebs Chapter 22 pages 447-448.
Outline for today:

I. Life tables (from last class)
II. Competition
a. Resource vs interference competition
b. Lotka-Volterra equations
c. Tilmans approach
d. Niches
Study questions
Explain the difference between resource and interference competition. Give an example
of each.
What do and in the Lotka-Volterra equations represent?
For the 4 general cases of the Lotka-Volterra equations, will in > or < in the following
inequalities, and describe whether inter- or intraspecific competition is more important for
species 1 and 2
K1 ___ K2/
K2 ___ K1/
What were Tilmans criticisms of the Lotka-Volterra approach? Describe Tilmans

approach to determining the outcome of competition between two species.
Suppose the densities of two species A and B are 60 and 30 organisms per acre. Their
carrying capacities are 65 and 80 organisms per acre, respectively. Can you say whether
or not these species could be in stable coexistence as described by the Lotka-Volterra
Equations? Why or why not? What if the densities of the two species are 20 and 20
organisms per acre, respectively. What can you say now?
1.018/7.30J
Lecture 17 Competition and Niches

READINGS:
Krebs Chapter 13: Species Interactions: Predation
Outline for today:

I. Finish competition
a. Tilmans approach
b. Competitive exclusion principle
c. Character displacement and resource partitioning
d. Fundamental and Realized Niches
Study questions
Explain the difference between a fundamental and a realized niche.

Explain character displacement and provide and example
Explain the significance of Gauses experiments with paramecium.
Gauses paramecium experiments
Fall 2003
Fundemental vs. realized niche
Independent vs. inter-dependent niches

(a)
(b)
(c)
A
B
A
B
Two species, A and B

(a) Niches are independent
(b) and (c) Niches are partially dependent
Macarthurs Warblers: See Krebs 12.15
Supplement to class (11/6):

Clarifying Tilmans approach:
Consider the graph for one species, Species A:
Suppose that Species A uses Resources 1

and 2 in the ratio of 2:1 (shown by the
dotted line)
Zone 1
R2
Zone 2
R1
If the supply point falls in Zone 1 (above the

line), then R1 will be limiting. In other
words, if Species A uses up the resources
at a constant 2:1 ratio, and the supply point
ratio of R1:R2 is less than 2:1, then Species
A will run out of R1 first.
Below the line, in Zone 2, R2 will be limiting.
For Species A, because the usage ratio of R1:R2 is greater than 1, Species A is more
efficient at using R2, and it is generally considered to be limited by R1. Whether or not it will
actually be limited by R1 depends on conditions in the environment (whether your starting
point is in Zone 1 or 2).
Consider the graph for Species B:

Now lets consider the case for Species B.
Zone 1
R2
Again in Zone 1 (above the dotted line),

Species B will be limited by R1, and below
the line will be limited by R2.
Zone 2
Generally speaking, Species B will be more

limited by R2, and is considered more
efficient at using R1.
R1
Species A and B together:

1 Species A and B both lose
CB
2 Species B wins over Species A
R2
2
CA
CA
5
3 Falls within Zone 1 for both Species A

and B. Hence, R1 will be limiting for
both. Since Species B is more efficient
at using R1, it will predominate.
4 Here, A will be limited by R1 and B will

be limited by R2. Since B is generally
A
1
more limited by R2 and A is generally
R1
limited by R1, neither species will have a
competitive advantage over the other
and both will be limited. This is the zone of coexistence. The stable equilibrium point will
occur at the intersection of the two lines (since dN/dt=0 for both species here).
6
5 Falls within Zone 2 for both Species, meaning that R2 will be limiting for both species.
Since Species A is more efficient at using R2, Species A will be able to outcompete
Species B in this region.
6 Species A wins over Species B

(a)
The axes in graphs on right represent

availability of two resources. The arrows
show the range of availabilities that will
permit the growth of Species A and B.
(b)
(c)
A
B
A
B
Lets consider the shape of the niche for just

Species A, in two dimensions. There are
three general shapes for the two-dimensional
niche.
Two species, A and B

(a) Niches are independent
(b) and (c) Niches are partially dependent
(1) No interdependence of niches. At high availability of R1, any level of R2 will permit growth.
(2) Interdependent niche. At high availability of R1 (e.g. bright sunlight for a plant), Species A
requires high availability of R2 (e.g. high water availability) in order to grow.
(3) Interdependent niche. This time, high availability of R1 permits Species A to grow only if
availability of R2 is low.
(1)
(2)
R2
(3)
R2
R2
A
R1
R1
R1
1.018/7.30J
Fall 2003
Lecture 18 Predation
READINGS:
Gilg O, I Hanski and B Sittler. 2003. Cyclic dynamics in a simple vertebrate predator-prey
community. Science. 302:866.
Turchin P, L Oksanen, et al. 2000. Are lemmings prey or predators? Nature. 405:562.
Tilman D. 2000. Causes, consequences and ethics of biodiversity. Nature. 405:208.
Ranta E. 2003. Making sense of complex population cycles. Science. 301:171.
Outline for today:

I. Predation
a. Lotka-Volterra
b. Rosenweig-MacArthur
c. Functional Response Curves -- Holling
II. Guest Speaker, Aladdine Joroff (00)
Lemmings: Predator or Prey?
Study Questions
What is unrealistic about Lotka-Volterras approach to modeling predator-prey

interactions? What other shapes can the isoclines assume?
What situations are stable and unstable in Rosenweig-MacArthurs approach? What
changes might make stable interactions unstable?
Sketch the Type I, II and III Functional Response Curves and describe what the shapes of
the curves mean.
According to Tilman, how does competition among members of a single trophic level
serve to stabilize communities? What are the requirements for coexistence?
Compare the findings of Gilg et al. and Turchin et al. Are their findings compatible with
each other?
In the Gilg et al. paper, what type of function response curves do the predators exhibit
with respect to lemming density?
Creating Stable Oscillations in Lab Settings

Adapted from Krebs Fig. 13.2
Huffaker
Oscillations in Natural Settings
Functional Responses:
Type II
Conservation Examples
Population Viability Analysis
- Butterflies and Restoration
Indicator Species
- Good idea?
Hotspots
Endangered Species
Part of declaring a species endangered involves
doing a Population Viability Analysis (PVA)
A population is not considered endangered if it has
95% chance of persisting for 100 years.
Once a species is declared endangered, it gets a
recovery plan
What will be done to help it
When is it considered recovered
Fenders Blue Butterfly

Pretty butterfly that lives in western Oregon
Lays eggs on Kincaids Lupine
Kincaids Lupine only grows in old growth prairies
Prairies are prime land for farms, suburbs, shopping malls,
universities
Both Kincaids Lupine and Fenders Blue Butterfly were recently
listed as endangered species.
Sources: Schultz and Hammond (2003) Conservation Biology 17:1372-1385.
Schultz (1998) Conservation Biology 12: 284-298
E. Crone, pers. comm.
Population Viability for Fenders Blue

Data:
Yearly population census in different patches
Assume:
Density independent growth
No observer error
No exceptional years
Use exponential growth equation

N(t+1) = N(t) + (r + ) N(t)
= error term
Growth rate and variance for Fenders Blue

Site
Ownership
Protected
status
Number
of
censuses
Average
population
sizec
Population
growth rate
( )
Butterfly
Meadowsd
Fern Ridge
Eaton Lane
Fern Ridge
Spires Lane
Fir Butte
Willow CreekBailey Hill
Willow CreekMain Area
Willow CreekNorth Area
Basket Butte
Gopher Valley
McTimmonds
Valley
Mill Creek
Oak Ridge
Private
Unprotected
412
1.06
Variance in
population
growth rate
2
( )
0.122
Public
Protected
2.66
1.461
Public
Protected
22
1.92
1.338
Public
Private
Protected
Protected
8
9
54
77
1.61
1.34
0.861
0.692
Private
Protected
738
1.15
0.387
Private
Protected
43
1.56
0.918
Public
Private
Public
Protected
Unprotected
Unprotectede
8
8
9
589
10
11
1.12
0.99
2.02
0.436
0.468
1.715
Public
Private
Unprotectede
Unprotected
10
9
17
149
1.31
1.21
0.607
0.448
Avg. growth rate = 1.49

Avg. variance = 0.79
(for sites with > 25 butterflies = 0.54)
Chance of Persistence
Multiple Patches = Metapopulation

Chance of survival with no colonization is:
survival anywhere = 1 - (1 - survivali)
i
Chance of survival WITH colonization will be higher
Metapopulation can survive even when all patches will

Individually go extinct
Prairie Restoration
Measure
Flight paths
Chance to leave lupine area
Daily time budget
Lifespan
Model different habitat configurations and ask which
increases survival the most.
Fenders Blue Butterflies:

Live ~ 10 days
Fly ~ 2.3 hours / day
Disperse within lupine ~ 3 m2/s
Disperse outside lupine ~ 15 m2/s
Weakly bias flight towards lupine patches
Butterfly might go 0.75 km within lupine
2 km outside of lupine
Historically, patches ~ 0.5 km apart
Now patches 3 - 30 km apart
Other Examples of Recommendations

Spotted Owls
Save old growth trees
Sea Turtles
Protect the adults, forget the eggs
Sea Otters
Based PVA on risks of oil spills,
recommend number and area for
recovery
Problem
Fenders Blue study:
8 years dedicated study by grad student, TNC personnel
Undergraduate field assistants
Lots of volunteers
Impossible to do for very many species
Indicator Species
A well-studied species whose protection will also protect
many other less weel-studied species.
What makes a good indicator?
Hot Spots
Places with high biodiversity, especially many endemic species
Brooks et al., (2002) Habitat loss and extinction in the hotspots of

biodiversity. Conservation Biology 16: 909-924.
Save Hotspots to Save Diversity?

Myers et. al. claim that 1.4% of land area contains
44% of vascular plants and 35% of vertebrates
Save 1.4% and you save a good bit of worlds
biodiversity
Myers et al., (2000) Biodiversity hotspots for conservation

priorities. Nature 403: 853-858.
10
Conclusions
Looks good, but
Tools of ecology help guide small, local decisions
At large scale, tools of ecology also offer guidance, but no

easy answers.
11
Outline for today

Components of an effective talk
A presentation about
giving a presentation
Laurel Schaider
1.018/7.30J Final Lecture
November 20, 2003
Components of presentation
Visual guidelines
Review
Conclusions
Setting the stage
Set the stage
You can have bullet points
Background
to tell the audience what
State the question/hypothesis
youre going to talk about
Describe your approach
but what might be better
Sample data
is a picture to really
Conclusions
set the stage
Picture of a fire along the side of a road.
Removed for copyright restriction.
See: http://www.nifc.gov/gallery/manter.html
Manter Fire Sequoia National Forest California (http://www.nifc.gov/gallery/manter.html
How can this be prevented?
www.nifc.gov -Sequoia National Forest California
http://www.nifc.gov/gallery/manter.html
What are we doing to rangeland genetic diversity?
http://www.nau.edu/~envsci/sisk/courses/env440/SCBS/andy.htm
Are we being
affected by
environmental
estrogens?
news.bbc.co.uk/hi/english/business/newsid_610000/610046.stm
www.njeit.org/examples.htm
http://www.ecology.com/dr-jacks-natural-world/most-important-organism/
Introduction
Why is your topic significant?
What have other people studied about it?
What is not known?
Manter Fire Sequoia National Forest California (http://www.nifc.gov/gallery/manter.html
State the Question/Hypothesis

What is the major question or hypothesis
you are testing?
You can have 1 or 2 or 3, but not too many
What role do chelated metals

play in total metal uptake?
Approach & methods
yrtem otyC w olF

Cells
Discuss approach
Briefly include important methods
Forward light
scatter detector
Laser
Site selection
Novel experimental techniques
DNA
per cell
Unfamiliar concepts
Pictures are very helpful here!

Prof. Chisholm
Pigment fluorescence
detector
Hypothesized results
Methods
Graphs are really helpful

Grow plants 4-6 weeks
2-3 days exposure metal-EDTA
solutions
Tables can be hard to read

Just one or two examples...You dont have
time to share all your hypothesized data
total metal GFAAS

FeEDTA- & total EDTA
HPLC, Nowack et al., 1996
Me-EDTA2- HPLC
Bedsworth & Sedlak, 2001
Winogradsky data
Winogradsky data
Meat
100
100
50
No Meat
80
60
100
% with
colors in
mud
80
% samples
% black
% with
bubbles
60
Meat
No meat
40
20
0
black
85k
50-60m,r
(4.7)s
Si te specificm
> 0.001t (not yet

maximized)
180s
(8.2)r
Up to
1,000,000s
Site specific
50 - 100u
(About 290 Mha
suitable globally
for this practice)
10v- 80i
(Depends on
land & water
cost, & value
of products)
40-60s
> 100
(Depends on
management
strategy)
1.2s
(2.2tC/ha-yr)w
>16.6s
(a) 1.4 - 4.1

(b)18 - 22
(c) 40y
(a) - 55 (!)
(b) 50
(c) 350-450s
Optimal rate to
be determined
(3.97.7tC/ha
-yr)s
0.4s
Up to
1,000,000s
Up to
1,000,000s
Site specific
Ecological
Risks
Hypoxia,
HABs, change
in species
composition
Ecos yst em
disruption due
to CO2 acidity p
Groundwater
impact, leakage
to bent hic zone
Groundwater
impact, land
absidence,
subsidence
Introduction of
alien species,
monoculturing,
land/water use
conflictss
Groundwater
impact, land
absidence,
subsidence
Low risk
Other Benefits
Stimulates fish
production?
None
None
Biofuels and
ot her product s,
wildlife habitat,
watershed
management.
Increased oil
recovery
Recovery of
methane
Effects of excess EDTA

95
0.1
0.08
0.06
% water
90
**
shoots
**
0.04
85
roots
0.02
0
**
*
*
control
(45 M
excess
EDTA)
500 M
excess
EDTA
Effects of excess EDTA

Deployment
Status
IRONEX I & II,
SO IREE, and
CARUSO field
experiments
DOE Testing off
Kona Island in
2001-2002?
Commercial pilot
at Sleipner in
North Sea.
Extends value
of reservoir site
**
80
500 M
excess
EDTA +
Cu, Fe, Mn, Zn
JI project in
Scolel Te,
Mexicox. Farm
management in
USA for CO2.
Commercial use
in North Sea &
West Texass.
Commercial
pilots in New
Mexico and
Australia.
95
0.1
0.08
0.06
% water
90
**
shoots
0.04
85
roots
0.02
0
**
*
control
(45 M
excess
EDTA)
500 M
excess
EDTA
80
500 M
excess
EDTA +
Cu, Fe, Mn, Zn
Conclusions & Implications

Tell them what you told them
Shoot water content (%)
Coal-bed CH4
100m-220q
Root or shoot dry weight (g)
Enhanced Oil
Recovery
>300m
(4.1)n
Agro-forestry
> 1,000
Depleted Oil &

Gas Reservoirs
Sequestration
Rate (GtC/yr)
1.52 (100 year
average)l
Re-iterate why it matters
Deep Ocean
Injection or
Diffusion
Ocean Aquifers
Residence
Time (years)
Varies with
durati on of
ocean
fertilisation
100-1000o
Shoot water content (%)
,h
($/tC)
1-15j
Gl obal annual CO2

avoidance & capture
target (GtC/yr)
3.5 + [rise in emissions]
Root or shoot dry weight (g)
Total Costg
Target reduction in
atmospheric CO2 over
next 100 years (GtC)
Approx. 850e
Approx. Global
Capacity (GtC)
152i
Atmospheric CO2
accumulation rate
(GtC/yr)
3.3 0.2d
CO2 Storage
Option f
Southern Ocean
Fe-Fertilisation
Residence time of
CO2 in the
atmosphere (yr)
50 - 200c
colors in mud
Potential further global

emissions from fossil
fuels (GtC)
659a -4000b
bubb les
Planning content
General hints on effective visuals
Consider knowledge of audience
Concise
Consider what makes an interesting story
Font
Ask rhetorical questions
Color
You cant say everything thats in your

proposal!
General hints on effective visuals

Dont use more words than are necessary
Choose a font style and size that will allow
your audience to see the words clearly
While colors can be very useful, choose
carefully and dont over-do it.
Bullet points
Bullet points
W atch out for alignment of bullets
There should be a space between bullet and
first word
And second line should be aligned
And there should be space between points
This will make the words easier to read
But you shouldnt have this many words in the
first place, this is more as an example
Beware the flying bullet
W atch out for alignment of bullets
Some people like the bullet points
There should be a space between bullet and

first word
To come flying in one-by-one
And second line should be aligned

And there should be space between points
This will make the words easier to read
This can interesting and amusing

But sometimes is distracting
Plus people sometimes like to have time to
read over all the points at their leisure
But you shouldnt have this many words in the

first place, this is more as an example
This is in size 30 font

.02 ezis tnoF amohaT

ni si sihT .tnof namoR weN semiT ni evah uoy ekil senil elttil esoht era
sfireS .sfires htiw stnof naht daer ot reisae era sfires tuohtiw stnoF
. 02 ezis tn oF S M snaS cimoC ni si sihT

.tnof namoR weN semiT ni evah uoy ekil senil elttil esoht era sfireS
.sfires htiw stnof naht daer ot reisae era sfires tuohtiw stnoF
Fonts without serifs are easier to read than fonts with serifs. Serifs are
those little lines like you have in Times New Roman font. This is in
Arial Font size 20.
Fonts without serifs are easier to read than fonts with serifs. Serifs are those
little lines like you have in Times New Roman font. This is in Times New
Roman Font size 20.

Colors can be used very effectively.
Fonts without serifs are easier to read than fonts with serifs. Serifs are
those little lines like you have in Times New Roman font. This is in
Palatino Font size 20.
Of course, color choice depends on your background.
Contrasting colors make a more dramatic effect than
Contrasting colors make a more dramatic effect than
really similar colors, which might not show up as

different.
really similar colors, which might not show up as

different.
Some colors show up better than others.
Some colors show up better than others.
Too many colors, well, are just too many colors.
Too many colors, well, are just too many colors.
Speaking of backgrounds
Beware of really busy or textured

backgrounds
Dark backgrounds with light writing can be really nice
These can be distracting

And also make the text harder to read
Problems:
Sometimes harder to make handouts
W astes a lot of ink if you want to photocopy
Can darken a room
There are many pre-set options
Engaging the audience

Eye contact
Some are interesting

Some are distracting
Choose carefully
Pace
Content Whos your audience?
biosphere
ecosystem
PRACTICE!
community
population
organism
Organism
Population
Metabolisms: sources of C, energy, e-
Population growth
heterotrophs
Intraspecific competition
photoautotrophs and chemolithoautotrophs
wolf
deer
wolf
moose
nutrients
deer
light
grass
moose
nutrients
light
grass

Community
Ecosystem
Interspecific competition
Productivity
Predation
Limiting nutrients
Food webs
Life
Surroundings
wo lf
wolf
deer
deer
moose
nutrients
light
moose
nutrients
grass
light
grass
Biosphere
What else is ecology?
Grassland
wolf
Biogeochemical cycles
deer
Climate change
Different biomes
moose
nutrients
Tropical ecology, marine ecology, etc.
light
grass
Different organisms
CO2
O2
Plants, microbes, animals
Tundra
Ocean
Evolutionary ecology
fish
fox
ferr et
Population & community ecology
mouse
nutrients
copepod
light
shrimp
nutrients
moss
light
algae
Want to learn more?

Department of Organismic & Evolutionary
Biology
Evolution of Plant Life in Geologic Time
Biological Oceanography
Tropical Insect Systematics
Global Change Biology
Topics in Marine Biology
Nature and Regulation of Marine Ecosystems
Ecology is a science
Forest Ecology
Ecology is a science
...but ecological principles can be applied
to other aspects of our lives
Thanks Sagol Gracias Shukriya

Merci Tashakkur Danke Takk
Salamat Arigato Komapsumnida
Xie xie Spasibo Tack Khawpkhun
Vinaka Ksznm Asante Nandri
Ngiyabonga Cm n Dakujem
Tapadh leat Dhannvaad Kongoi
Gratia Makasih Dankie Shukran

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Fundamentals of Ecology

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What are the main definitions of ecology discussed?

What are the main definitions of ecology discussed?

What are some of the levels of organization in ecology?

What are some of the levels of organization in ecology?

1.018/7.

Lecture 1 Introduction to Ecology

Outline for today:

RECITATIONS NEXT WEEK

What ecology is not

Why study ecology?

III. How to study ecology?

adapted from Elements of

IV. Where to study ecology?

Population: Group of interacting and interbreeding organisms.

V. How will we learn about ecology?

Lecture 2 Carbon and Energy Transformations

underpin biogeochemical systems. Science. 296:1071. (L)

Sarbu, S et al. 1996. A chemoautotrophically-based cave ecosystem. Science. 272:1953. (L)

Novel genetic identification techniques (C Woese in the 1970s)

Tree of Life with 3 Domains: Eubacteria, Archaea, Eukaryotes

Hydrothermal vents and hot springs

Genotypic not phenotypic classifications

Universal phylogenetic tree based on SSU rRNA sequences

Billions of years before present

Origin of life 3.8 billion years ago

Formation of Earth 4.5 billion years ago

Basic picture of life:

CO2 and H2O

B. Bacterial Photosynthesis (anaerobic)

Energy Source? Reduced inorganic compounds (CH4, NH4, H2S, Fe2+)

CH4 (methane) CO2

NH4+ NO2- NO3

ATP = adenosine triphosphate. (ADP = adenosine DI phosphate)

CO2 CH4 (methane)

Lecture 3 Primary Productivity

Questions for today:

(A) Metabolism of a Cell

(B) Metabolism of a Drop of the Ocean

(C) Metabolism of an Ocean

Deep Sea Sediments

B. Residence times and turnover rates

Adapted from: Begon,1996

Comparison of Young and Mature

Ecosystems (in order

Mean net primary

World net primary

Source: Smith, 2001.

Near ir / red reflectance

Leaf area index (m2/m2)

Net primary production

Adapted from: Smith, 2001.

Net productivity above ground per year (g/m2)

200 400 600 800 1000 1200

Adapted from Krebs

NPP (nmol CO2 g-1 s-1)

Leaf nitrogen (mmol g-1)

Terrestrial NPP Co-opted by Humans

NPP Co-opted (Pg)

Consumed on natural grazing lands

Burned on Natural Grazing Lands