copyright © 2005 pearson education, inc. publishing as benjamin cummings quantifying communities...

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Quantifying Communities Community structure is measured in different ways.

Species Richness: The number of _______species in the community

Species Diversity: The number and _________of species in thecommunity


Are All Ecosystems Equal?

Different ecosystems have different amounts of biodiversity (and produce different amounts of _________)


Diversity = Stability

There is a direct relationship between biodiversity in an ecosystem and the stability of the ecosystem.

Genetic Diversity

Species Diversity

Biome Diversity


Ch 55: Ecosystems

• Ecosystems, Energy, and Matter

• An ecosystem consists of all the organisms living in a community (___________ factors) and all the abiotic factors with which they rely on


The only constant is change

Ecosystems are constantly changing.

Disturbance: Anything that disrupts the homeostatic balance of an ecosystem.


How does Energy and Chemical movement

different through ecosystems?

Figure 54.2

Microorganismsand other

detritivores

Detritus

Primary producers

Primary consumers

Secondaryconsumers

Tertiary consumers

Heat

Sun

Key

Chemical cycling

Energy flow


Trophic Efficiency

-Only __% of Sun’s energy reaches the earth -Most energy does ____ move up the food chain


We measure Productivity with Pyramids!

-Pyramid of Energy-Shows that within a food chain, only ~___% of energy at any trophic level will be passed on to the next trophic level.

Figure 54.11

Tertiaryconsumers

Secondaryconsumers

Primaryconsumers

Primaryproducers

1,000,000 J of sunlight

10 J

100 J

1,000 J

10,000 J


Biomass also measures Productivity

Energy is added in to a community by _______. Pyramids of Biomass show that ________ usually occupy the greatest biomass in the ecosystem.

Figure 54.12a

(a) Most biomass pyramids show a sharp decrease in biomass at successively higher trophic levels, as illustrated by data froma bog at Silver Springs, Florida.

Trophic level Dry weight(g/m2)

Primary producers

Tertiary consumers

Secondary consumers

Primary consumers

1.5

11

37809


Pyramids of Numbers

• A pyramid of numbers represents the number of __________ in each trophic level

Figure 54.13

Trophic level Number of individual organisms

Primary producers

Tertiary consumers

Secondary consumers

Primary consumers

3

354,904

708,624

5,842,424


• Certain aquatic ecosystems

– Have inverted biomass pyramids

Figire 54.12b

Trophic level

Primary producers (phytoplankton)

Primary consumers (zooplankton)

(b) In some aquatic ecosystems, such as the English Channel, a small standing crop of primary producers (phytoplankton)supports a larger standing crop of primary consumers (zooplankton).

Dry weight(g/m2)

21

4


Primary Productivity

is the amount of light energy converted to chemical energy by autotrophs during a given time period

Does all of the energy absorbed the sun go into the bodies (biomass) of producers?


Productivity

How is Gross primary productivity (GPP) different from net primary productivity (NPP)?

NPP = GPP – (metabolism + lost energy)


Are all ecosystems equally productive?

Does productivity fluctuates seasonally, and with climate?


Different ecosystems vary in their net primary production– And in their contribution to the total NPP on Earth

Lake and stream

Open ocean

Continental shelf

Estuary

Algal beds and reefs

Upwelling zones

Extreme desert, rock, sand, ice

Desert and semidesert scrub

Tropical rain forest

Savanna

Cultivated land

Boreal forest (taiga)

Temperate grassland

Tundra

Tropical seasonal forestTemperate deciduous forest

Temperate evergreen forest

Swamp and marsh

Woodland and shrubland

0 10 20 30 40 50 60 0 500 1,000 1,500 2,000 2,500 0 5 10 15 20 25

Percentage of Earth’s netprimary production

Key

Marine

Freshwater (on continents)

Terrestrial

5.2

0.3

0.1

0.1

4.7

3.53.3

2.9

2.7

2.41.8

1.7

1.6

1.5

1.3

1.0

0.4

0.4

125

360

1,500

2,500

500

3.0

90

2,200

900

600

800

600

700

140

1,600

1,2001,300

2,000

250

5.6

1.2

0.9

0.1

0.040.9

22

7.99.1

9.6

5.4

3.50.6

7.1

4.9

3.8

2.3

0.3

65.0 24.4

Figure 54.4a–c

Percentage of Earth’ssurface area

(a) Average net primaryproduction (g/m2/yr)(b) (c)


• Overall, terrestrial ecosystems contribute about two-thirds of global NPP and marine ecosystems about one-third

Figure 54.5

180 120W 60W 0 60E 120E 180

North Pole

60N

30N

Equator

30S

60S

South Pole


Matter Cycles

Matter cycles between abiotic and ________ reservoirs in an ecosystem


Producers & Decomposers

Producers move matter from ______ sources (sun, soil) to biotic sources.

Decomposers move matter from biotic sources to abiotic sources.


Nutrients cycle through ecosystems• Decomposers or detritivores (mainly bacteria and

fungi) recycle essential elements by decomposing organic material and returning elements to inorganic reservoirs

Figure 54.3


What are the Limiting Factors in Marine Ecosystems?

Figure 54.6

(a) Phytoplankton biomass and phosphorus concentration (b) Phytoplankton response to nutrient enrichment

GreatSouth Bay

MorichesBay

ShinnecockBay

Startingalgal

density

2 4 5 11 30 15 19 21

30

24

18

12

6

0

Unenriched control

Ammonium enrichedPhosphate enriched

Station number

Ph

yto

pla

nkt

on

(mill

ion

s o

f ce

lls p

er

mL

)

87

6

5

4

3

2

1

02 4 5 11 3015 19 21

87

6

54

32

1

0

Ino

rga

nic

ph

osp

ho

rus

(g

ato

ms/

L)

Ph

yto

pla

nkt

on

(mill

ion

s o

f ce

lls/m

L)

Station number

CONCLUSION Since adding phosphorus, which was already in rich supply, had no effect on Nannochloris growth, whereas adding nitrogen increased algal density dramatically, researchers concluded that nitrogen was the nutrient limiting phytoplankton growth in this ecosystem.

Phytoplankton

Inorganicphosphorus

RESULTS Phytoplankton abundance parallels the abundance of phosphorus in the water (a). Nitrogen, however, is immediately taken up by algae, and no free nitrogen is measured in the coastal waters. The addition of ammonium (NH4

) caused heavy phytoplankton growth in bay water, but the addition of phosphate (PO4

3) did not induce algal growth (b).


• Experiments in another ocean region

– Showed that iron limited primary production

Table 54.1


What happens when you have too many nutrients?

• Eutrophication of lakes (algae on top prevent light from reaching bottom, dead algae add to biomass and all decrease Oxygen which kills fish, etc

Figure 54.7


• Worldwide agriculture could successfully feed many more people

– If humans all fed more efficiently, eating only ________

Figure 54.14

Trophic level

Secondaryconsumers

Primaryconsumers

Primaryproducers


• A general model of nutrient cycling

– Includes the main reservoirs of elements and the processes that transfer elements between reservoirs

Figure 54.16

Organicmaterialsavailable

as nutrients

Livingorganisms,detritus

Organicmaterialsunavailableas nutrients

Coal, oil,peat

Inorganicmaterialsavailable

as nutrients

Inorganicmaterialsunavailableas nutrients

Atmosphere,soil, water

Mineralsin rocksFormation of

sedimentary rock

Weathering,erosion

Respiration,decomposition,excretion

Burningof fossil fuels

Fossilization

Reservoir a Reservoir b

Reservoir c Reservoir d

Assimilation, photosynthesis


Biogeochemical Cycles

• What drives the water cycle versus the Carbon cycle?

Figure 54.17

Transportover land

Solar energy

Net movement ofwater vapor by wind

Precipitationover ocean

Evaporationfrom ocean

Evapotranspirationfrom land

Precipitationover land

Percolationthroughsoil

Runoff andgroundwater

CO2 in atmosphere

Photosynthesis

Cellularrespiration

Burning offossil fuelsand wood

Higher-levelconsumersPrimary

consumers

DetritusCarbon compounds in water

Decomposition

THE WATER CYCLE THE CARBON CYCLE


How does Nitrogen enter and leave ecosystems?


Decomposition and Nutrient Cycling Rates

• Decomposers (detritivores) play a key role

– In the general pattern of chemical cycling

Figure 54.18

Consumers

Producers

Nutrientsavailable

to producers

Abioticreservoir

Geologicprocesses

Decomposers


Why is Phosphorus considered more of a Local nutrient?


• How does human activity affect ecosystems?

Figure 54.19c(c) The concentration of nitrate in runoff from the deforested watershed was 60 times

greater than in a control (unlogged) watershed.

Nitr

ate

co

nce

ntr

atio

n in

ru

no

ff(m

g/L

)

Deforested

Control

Completion oftree cutting

1965 1966 1967 1968

80.0

60.0

40.0

20.0

4.0

3.02.0

1.0

0


Agriculture and Nitrogen Cycling

• Agriculture constantly removes nutrients from ecosystems

– That would ordinarily be cycled back into the soil

Figure 54.20


• Nitrogen is the main nutrient lost through agriculture

– Thus, agriculture has a great impact on the nitrogen cycle

• Industrially produced fertilizer is typically used to replace lost nitrogen

– But the effects on an ecosystem can be harmful


Contamination of Aquatic Ecosystems

• The critical load for a nutrient

– Is the amount of that nutrient that can be absorbed by plants in an ecosystem without damaging it


• When excess nutrients are added to an ecosystem, the critical load is exceeded

– And the remaining nutrients can contaminate groundwater and freshwater and marine ecosystems


• Sewage runoff contaminates freshwater ecosystems

– Causing cultural eutrophication, excessive algal growth, which can cause significant harm to these ecosystems


Acid Precipitation

• Combustion of fossil fuels

– Is the main cause of acid precipitation


• North American and European ecosystems downwind from industrial regions

– Have been damaged by rain and snow containing nitric and sulfuric acid

Figure 54.21

4.6

4.64.3

4.14.3

4.6

4.64.3

Europe

North America


• By the year 2000

– The entire contiguous United States was affected by acid precipitation

Figure 54.22

Field pH5.35.2–5.35.1–5.25.0–5.14.9–5.04.8–4.94.7–4.84.6–4.74.5–4.64.4–4.54.3–4.44.3


• Environmental regulations and new industrial technologies

– Have allowed many developed countries to reduce sulfur dioxide emissions in the past 30 years


Toxins in the Environment

• Humans release an immense variety of toxic chemicals

– Including thousands of synthetics previously unknown to nature

• One of the reasons such toxins are so harmful

– Is that they become more concentrated in successive trophic levels of a food web


• In biological magnification

– Toxins concentrate at higher trophic levels because at these levels biomass tends to be lower

Figure 54.23

Con

cent

ratio

n of

PC

Bs

Herringgull eggs124 ppm

Zooplankton 0.123 ppm

Phytoplankton 0.025 ppm

Lake trout 4.83 ppm

Smelt 1.04 ppm


• In some cases, harmful substances

– Persist for long periods of time in an ecosystem and continue to cause harm


Atmospheric Carbon Dioxide

• One pressing problem caused by human activities

– Is the rising level of atmospheric carbon dioxide


Rising Atmospheric CO2

• Due to the increased burning of fossil fuels and other human activities

– The concentration of atmospheric CO2 has been steadily increasing

Figure 54.24

CO

2 c

onc

en

trat

ion

(pp

m)

390

380

370

360

350

340

330

320

310

3001960 1965 1970 1975 1980 1985 1990 1995 2000 2005

1.05

0.90

0.75

0.60

0.45

0.30

0.15

0

0.15

0.30

0.45

Te

mp

era

ture

va

ria

tion

(

C)

Temperature

CO2

Year


How Elevated CO2 Affects Forest Ecology: The FACTS-I Experiment

• The FACTS-I experiment is testing how elevated CO2

– Influences tree growth, carbon concentration in soils, and other factors over a ten-year period

Figure 54.25


The Greenhouse Effect and Global Warming

• The greenhouse effect is caused by atmospheric CO2

– But is necessary to keep the surface of the Earth at a habitable temperature


• Increased levels of atmospheric CO2 are magnifying the greenhouse effect

– Which could cause global warming and significant climatic change


Depletion of Atmospheric Ozone

• Life on Earth is protected from the damaging effects of UV radiation

– By a protective layer or ozone molecules present in the atmosphere


• Satellite studies of the atmosphere

– Suggest that the ozone layer has been gradually thinning since 1975

Figure 54.26

Ozo

ne la

yer

thic

knes

s (D

obso

n un

its)

Year (Average for the month of October)

350

300

250

200

150

100

50

01955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005


• The destruction of atmospheric ozone

– Probably results from chlorine-releasing pollutants produced by human activity

Figure 54.27

1

2

3

Chlorine from CFCs interacts with ozone (O3),forming chlorine monoxide (ClO) and oxygen (O2).

Two ClO molecules react, forming chlorine peroxide (Cl2O2).

Sunlight causes Cl2O2 to break down into O2 and free chlorine atoms. The chlorine atoms can begin the cycle again.

Sunlight

Chlorine O3

O2

ClO

ClO

Cl2O2

O2

Chlorine atoms


• Scientists first described an “ozone hole”

– Over Antarctica in 1985; it has increased in size as ozone depletion has increased

Figure 54.28a, b

(a) October 1979 (b) October 2000

copyright © 2005 pearson education, inc. publishing as benjamin cummings quantifying communities...

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