1

7.0147.014

Lecture 1: Introduction to Lecture 1: Introduction to Ecology and the BiosphereEcology and the Biosphere

Feb. 7 2007Feb. 7 2007

BIOSPHERE

ATOM

ORGANISMPOPULATION

COMMUNITY

ECOSYSTEMHierarchical Hierarchical

Organization and Organization and EcologyEcology

CELLMOLECULE

©© GBRMPA

©© GBRMPA

2

GlacierBay

Alaska

One successionalpathway:

Soils exposed less than 20 years:willow and Dryas

Soils exposed 45-80 years:sitka alder, scatteredcottonwood

Soils exposed 100years: sitka, alder,scattered spruce

Soils exposed150-200 years:dense sitkaspruce andwestern hemlock

Glacier Bay

Direction ofglacial retreat

20 km

N

Figure 50.12a

Youngest CommunityYoungest Community

Oldest CommunityOldest Community

NN22 fixationfixation

3

Early-mid successional Late-mid successional Climax

Alder – roots fix nitrogen

SpruceHemlock

Freeman Figure 50.12

Primary Succession at Glacier Bay

300

200

100

Year

Youngest Moraine Oldest Moraine

1 50 100 150 200

In mineral soil

In forest floor

Nitrogen Concentration(g per m2 of surface)

Nitrogenaseenzyme

NN ≡

NN ≡

Substrate, N2

Binding of Substrate

+ 2H

NN = NN −

+ 2H+ 2H

N N

Free Nitrogenase can bind another molecule of N2

Release of ProductReduction

Reduction Reduction

H

H HH

H

H

Product: Ammonia, NH3

NHH

HNH

H

H

Nitrogen Fixation

Adapted from: LIFE: The Science of Biology. Purves, Orians, and Heller, 2001

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Industrial N fixation

100

140biologicalfixation

200denitrification

SOIL

ATMOSPHERE

OCEANS

15biologicalfixation

110denitrification

1200internal cycling 8000

internal cycling10

burial

36river flow

groundwater

The Global Nitrogen Cycle Gigatons yr-1

<3fixation bylightening

1 1 GtGt ““gigatongigaton””

= 10= 1099 tonton= 10= 101515 gg= 1 billion = 1 billion

Industrial N fixation

100

140biologicalfixation

200denitrification

SOIL

ATMOSPHERE

OCEANS

15biologicalfixation

140denitification

1200internal cycling 8000

internal cycling?

burial

?river flow

<3fixation bylightening

groundwater

Nitrogen “Cycle” Without Microbes

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Life on Earth Today: AbridgedLife on Earth Today: Abridged(Photosynthesis = Respiration)(Photosynthesis = Respiration)

CO2 + H2Ocarbon waterdioxide (gas)

“CH“CH22O” +O” + OO22organicorganic oxygen oxygen carboncarbon (solid)(solid)

Plants Phytoplankton

Animals Bacteria

Chemical energy or

heat

Respiration

PhotosynthesisSolar energySolar energy

N,P,S,Fe….

Photosynthesis

Respiration

Glucose

2 NADH

2 ATP

2 Pyruvate

Cytoplasm Mitochondrion

2 NADH

2 CO2

2 Acetyl CoA Krebscycle

2 ATP

4 CO2

6 NADH2 FADH2

Glucose

3 CO2

PhotonCALVIN CYCLE

2H2O 4H+ + O24e–

ATPPhotosystem I

4e–

4e–

2 NADPH

2 NADP+ + 2H+

Photosystem II

3 ATP

3 ADP 6 ADP

6 ATP

6 NADP+ + 6H+

6 NADPH

Freeman, Figures 6.9, 7.10a, and 7.13Freeman, Figures 6.9, 7.10a, and 7.13

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BiologicalPump

CirculationGeological Reservoir

Photosynthesis

Gas exchange between air and

ocean

Net accumulationin ocean

Respiration

Land usechangesCombustion After Post et al., 1998

5.3

100-120

0.6-2.6

90-120

1.6-2.4

100-115 100-115

GtC yr-1

The Global Carbon cycleThe Global Carbon cycle

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CO

CO

2 2 C

once

ntra

tion

in A

tmos

pher

e (p

arts

per

mill

ion)

Con

cent

ratio

n in

Atm

osph

ere

(par

ts p

er m

illio

n)

YearYear

P>RP>R

R >PR >P

Emergent PropertyEmergent Property

from SeaWiFs Project website

Atmospheric Carbon Dioxide (Mauna Loa)Atmospheric Carbon Dioxide (Mauna Loa)

WinterWinterR > PR > P

SummerSummerP > RP > R

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EARLYEARLY Life on Earth: AbridgedLife on Earth: Abridged(Photosynthesis > Respiration)(Photosynthesis > Respiration)

CO2 + H2Ocarbon waterdioxide (gas)

“CH“CH22O” +O” + OO22organicorganic oxygen oxygen carboncarbon (solid)(solid)

Plants Phytoplankton

Animals Bacteria

Chemical energy or

heat

Respiration

PhotosynthesisSolar energySolar energy

N,P,S,Fe….

4

3

2

1

0

Formation of Earth 4.5 billion years ago

Chemical evolutionPhotochemical synthesis

EukaryotesEubacteria

ArchaebacteriaProkaryotes

Oxygenic phototrophs(cyanobacteria)

Development ofozone shield

Modern eukaryotes

Metazoans

Dinosaurs

Car

bon

buria

l

Today: Release offossil carbon

00.1%

01%

10%

20%

21%

% O2 inatmosphere

Billi

ons

of y

ears

bef

ore

pres

ent

Mar

ine

orig

inB

ande

d iro

nfo

rmat

ions

Terr

estr

ial o

rigin

Red

bed

s

Origin of life – 3.8 billion years ago

Anoxygenic phototrophs(photosynthetic bacteria)

Adapted from Brock and Madigan, Biology of Microorganisms

CO2 + H2O “CH2O” + O2 ↑

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Banded iron Banded iron formationsformations Red bedsRed beds

Freeman Textbook Figure 25.7

Absorption of Oxygen Released to Primitive Atmosphere

FeFe2+2+ + O+ O2 2 →→ FeOFeO33

Oceanic originOceanic origin Terrestrial originTerrestrial origin

Present Day Planetary Atmospheres Mars Earth Venus

CO2 95 % 0.035 % 98 %

N2 2.5 % 78 % 2 %

O2 0.25 % 21 % Trace

H2O 0.1 % 1 % 0.05 %

Temp (°C) -53 16 474 Adapted from Slesinger, W. 1991. Biogeochemistry: An Analysis of Global Change. Academic

Press. P.34

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Similar processes at all scalesSimilar processes at all scales

““Ecosphere”Ecosphere”

O2CO2

CO2

N,P,S,Fe….

GLUCOSE OXIDATION

Glucose

2 NADH

2 ATP

2 Pyruvate

Cytoplasm Mitochondrion

2 NADH

2 CO2

2 Acetyl CoA Krebscycle

2 ATP

4 CO2

6 NADH2 FADH2

Glucose

3 CO2

PhotonCALVIN CYCLE

In the Z scheme, electrons flow from water to NADPH.

2H2O 4H+ + O24e–

ATPPhotosystem I

4e–

4e–

2 NADPH

2 NADP+ + 2H+

Photosystem II

3 ATP

3 ADP 6 ADP

6 ATP

6 NADP+ + 6H+

6 NADPH

GLUCOSE OXIDATION

Glucose

2 NADH

2 ATP

2 Pyruvate

Cytoplasm Mitochondrion

2 NADH

2 CO2

2 Acetyl CoA Krebscycle

2 ATP

4 CO2

6 NADH2 FADH2

Glucose

3 CO2

PhotonCALVIN CYCLE

In the Z scheme, electrons flow from water to NADPH.

2H2O 4H+ + O24e–

ATPPhotosystem I

4e–

4e–

2 NADPH

2 NADP+ + 2H+

Photosystem II

3 ATP

3 ADP 6 ADP

6 ATP

6 NADP+ + 6H+

6 NADPH

BiosphereBiosphere CellCell

Molecular EcologyMolecular Ecology

Viewing the BiosphereViewing the Biosphereas a network of genesas a network of genes

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A Sea of A Sea of OrgansimsOrgansimsA Network of GenesA Network of Genes

(“dissolved information”)(“dissolved information”)Is…

aaggttttaaaatt

aaggttttccccttaaaatt

ccccttaaaatt

ttccccttaaaatt

aaccccttaaaatt

aaggttttcc

aaggttccttaaaatt

aaggttttccaa

tt

aaggttttaaaatt

aaggttttcccctttt

aaggttttccccttaaaatt

aaggttcctta

aaatt

1 billion microbes per liter

99.9 % have not been cultivated

information content of 1 liter = that in human genome

most of unknown function

Craig VenterWired MagazineAugust 2004

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Scorcerer II Expedition

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Challenger Expedition

2 April 2004 Science2 April 2004 Science

1.2 million new genes1.2 million new genes

1800 new ‘species’1800 new ‘species’

Craig Venter Takes on the Challenge

Estimated genetic inventory of Estimated genetic inventory of the planet: 20the planet: 20--30 billion genes.30 billion genes.

Most of them microbialMost of them microbial

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Take Home MessagesEcology – life at different scales

Emergent Properties

Organism ↔ Environment TWO WAY

Life has shaped Earth’s features

Biosphere - geosphere have co-evolved

Genetic inventory unknown

Microbes Rule!