EcosystemsEcosystems

Chapter 48Chapter 48

EcosystemsEcosystems

Open systems through which energy flows and Open systems through which energy flows and materials are recycledmaterials are recycled

Require energy and nutrient input and generate Require energy and nutrient input and generate energy and nutrient outputenergy and nutrient output

Modes of NutritionModes of Nutrition

AutotrophsAutotrophs Capture sunlight or chemical energyCapture sunlight or chemical energy ProducersProducers

HeterotrophsHeterotrophs Extract energy from other organisms or organic Extract energy from other organisms or organic

wasteswastes Consumers, decomposers, detritivoresConsumers, decomposers, detritivores

Simple Simple Ecosystem Ecosystem

ModelModelenergy input from sun

nutrientcycling

PHOTOAUTOTROPHS(plants, other producers)

HETEROTROPHS(consumers, decomposers)

energy output (mainly heat)

Consumers Consumers Herbivores Herbivores

Carnivores Carnivores

ParasitesParasites

Omnivores Omnivores

DecomposersDecomposers Fungi, bacteriaFungi, bacteria

Detritivores Detritivores Small invertebratesSmall invertebrates

SPRING

rodents, rabbits

fruits

insects

birds

SUMMER

rodents, rabbits

fruits

insects

birds

Seasonal variation in the diet of an omnivore (red fox)

Trophic LevelsTrophic LevelsWho Eats Whom?Who Eats Whom?

All the organisms at a trophic level are the All the organisms at a trophic level are the

same number of steps away from the energy same number of steps away from the energy

input into the systeminput into the system

Producers are closest to the energy input and Producers are closest to the energy input and

are the first trophic levelare the first trophic level

Trophic Levels in PrairieTrophic Levels in Prairie

5th

4th

3rd

2nd

1st

Fourth-level consumers (heterotrophs):

Top carnivores, parasites, detritivores, decomposers

Third-level consumers (heterotrophs):

Carnivores, parasites, detritivores, decomposers

Second-level consumers (heterotrophs):

Carnivores, parasites, detritivores, decomposers

First-level consumers (heterotrophs):

Herbivores, parasites, detritivores, decomposers

Primary producers (autotrophs):

Photoautotrophs, chemoautotrophs

Food ChainFood Chain

A straight-line sequence A straight-line sequence

of who eats whom of who eats whom

Simple food chains are Simple food chains are

rare in naturerare in nature

marsh hawk

upland sandpiper

garter snake

cutworm

plants

Tall-Grass Prairie Food WebTall-Grass Prairie Food Web

earthworms, insects

sparrow

vole pocketgopher

groundsquirrel

coyotebadgerweasel

spider

frog

snake

sandpiper crow

marsh hawk

grasses, composites

Energy Losses Energy Losses

Energy transfers are never 100 percent efficientEnergy transfers are never 100 percent efficient

Some energy is lost at each stepSome energy is lost at each step

How?How?

HeatHeat

Limits the number of trophic levels in an ecosystem Limits the number of trophic levels in an ecosystem

Two Types of Food WebsTwo Types of Food Webs

Producers (photosynthesizers)

Energy Input: Energy Input:

herbivores

carnivores

decomposers

decomposers

detritivores

energy in organic wastes, remains

Energy Output

Energy Output

energy lossesas metabolic heat & as net export from ecosystem

Producers (photosynthesizers)

decomposers

detritivores

Transfers: Transfers:

Grazing Food Web

Detrital Food Web

energy in organic wastes, remains

energy lossesas metabolic heat & as net export from ecosystem

Figure 48.7Page 871 

Biological MagnificationBiological Magnification

A nondegradable or slowly degradable A nondegradable or slowly degradable

substance becomes more and more substance becomes more and more

concentrated in the tissues of organisms at concentrated in the tissues of organisms at

higher trophic levels of a food webhigher trophic levels of a food web

DDT in Food WebsDDT in Food Webs

Effective chemical for killing mosquitoesEffective chemical for killing mosquitoes Accumulates in fatty tissuesAccumulates in fatty tissues Synthetic pesticide banned in United States since Synthetic pesticide banned in United States since

the 1970sthe 1970s Still persist in sedimentsStill persist in sediments

Birds that are carnivores accumulate DDT in their Birds that are carnivores accumulate DDT in their tissues, produce brittle egg shellstissues, produce brittle egg shells

DDT in an Estuary (1967)DDT in an Estuary (1967)DDT Residues (ppm wet weight of whole live organism)

Ring-billed gull fledgling (Larus delawarensis)Herring gull (Larus argentatus)Osprey (Pandion haliaetus)Green heron (Butorides virescens)Atlantic needlefish (Strongylira marina)Summer flounder (Paralychthys dentatus)Sheepshead minnow (Cyprinodon variegatus)Hard clam (Mercenaria mercenaria)Marsh grass shoots (Spartina patens)Flying insects (mostly flies)Mud snail (Nassarius obsoletus)Shrimps (composite of several samples)Green alga (Cladophora gracilis)Plankton (mostly zooplankton)Water

75.5 18.5 13.8 3.57 2.07 1.28 0.940.420.33 0.30 0.26 0.16 0.083 0.040 0.00005

Primary ProductivityPrimary Productivity GrossGross primary productivity is ecosystem’s total rate of primary productivity is ecosystem’s total rate of

photosynthesis for the ecosystem during an intervalphotosynthesis for the ecosystem during an interval

NetNet primary productivity is rate at which producers store energy primary productivity is rate at which producers store energy

in tissues in excess of their aerobic respirationin tissues in excess of their aerobic respiration

NPP accounts for the organic mass of plants (growth) and represents storage of NPP accounts for the organic mass of plants (growth) and represents storage of

chemical energy available to consumers. chemical energy available to consumers.

NPP = GPP - RespirationNPP = GPP - Respiration

Primary Productivity VariesPrimary Productivity Varies

Seasonal variationSeasonal variation

Variation by habitatVariation by habitat

The harsher the environment, the The harsher the environment, the

slower plant growth, the lower the slower plant growth, the lower the

primary productivity primary productivity

Ecological PyramidsEcological Pyramids Biomass PyramidBiomass Pyramid has tiers symbolizing the total dry weight of all has tiers symbolizing the total dry weight of all

organisms in an ecosystem's levels at any given organisms in an ecosystem's levels at any given time.time.

Biomass represents chemical energy stored in the Biomass represents chemical energy stored in the organic matter of a trophic level. organic matter of a trophic level.

Most narrow sharply from producers at the base to Most narrow sharply from producers at the base to top-level carnivores at the top. top-level carnivores at the top.

Silver Springs StudySilver Springs Study

Aquatic ecosystem in FloridaAquatic ecosystem in Florida Site of a long-term study of a grazing food webSite of a long-term study of a grazing food web

5

decomposers, detritivores(bacteria, crayfish)

1.5

1.1

37

third-level carnivores(gar, large-mouth bass)

second-level consumers(fishes, invertebrates)

first-level consumers(herbivorous fishes,turtles, invertebrates)

primary producers (algae,eelgrass, rooted plants)

809

g/m2

Energy PyramidEnergy Pyramid Reflects trophic structure most accurately because it Reflects trophic structure most accurately because it

is based on energy looses at each levelis based on energy looses at each level

Pyramid of Energy FlowPyramid of Energy Flow

Primary producers trapped about 1.2 percent of Primary producers trapped about 1.2 percent of the solar energy that entered the ecosystemthe solar energy that entered the ecosystem

6-16% passed on to next level6-16% passed on to next level (10%) (10%)

21

383

3,368

20,810 kilocalories/square meter/year

top carnivores

carnivores

herbivores

producers

decomposers + detritivores = 5,080

Figure 48.11Page 874

Energy Flow In Energy Flow In Silver SpringsSilver Springs

20,810 1,679,190

Incoming solar energy not harnessed: 1,679,190 (98.8%)

ENERGY INPUT:

1,700,000 kilocalories

20,810 (1.2%)

Producers

To next trophic level:

Energy in organic wastes and remains:

Energy losses as metabolic heat & as net export from ecosystem:

Herbivores

Carnivores

Top carnivores

Decomposers, detritivores

4,245

720

5

90

3,368

383

21

13,197

2,265

272

16

5,060ENERGY OUTPUT:

Total annual energy flow: 1,700,000 (100%)Figure 48.12

Page 874

All Heat in the EndAll Heat in the End

At each trophic level, the bulk of the energy At each trophic level, the bulk of the energy received from the previous level is used in received from the previous level is used in metabolismmetabolism

This energy is released as heat energy and lost This energy is released as heat energy and lost to the ecosystemto the ecosystem

Eventually all energy is released as heatEventually all energy is released as heat

Biogeochemical CycleBiogeochemical Cycle

Influence the availability of essential elements Influence the availability of essential elements

in ecosystemsin ecosystems

The amount of nutrients cycling is greater The amount of nutrients cycling is greater

than those entering or leavingthan those entering or leaving

Main reservoir for the nutrient is in the Main reservoir for the nutrient is in the

environmentenvironment

Environmental Inputs Environmental Inputs of Nutrientsof Nutrients

PrecipitationPrecipitation MetabolismMetabolism WeatheringWeathering

Environmental Outputs Environmental Outputs of Nutrientsof Nutrients

RunoffRunoff EvaporationEvaporation

Three CategoriesThree Categories

Hydrologic cycleHydrologic cycle WaterWater

Atmospheric cycles Atmospheric cycles Nitrogen and carbonNitrogen and carbon

Sedimentary cycles Sedimentary cycles Phosphorus and sulfurPhosphorus and sulfur

Hydrologic CycleHydrologic CycleAtmosphere

Ocean Land

evaporation from ocean

425,000

precipitation into ocean 385,000

evaporation from land plants (evapotranspiration)

71,000

precipitation onto land 111,000

wind-driven water vapor40,000

surface and groundwater flow 40,000

Figure 48.14Page 876

Hubbard Brook ExperimentHubbard Brook Experiment

A watershed was experimentally stripped of A watershed was experimentally stripped of

vegetationvegetation

All surface water draining from watershed was All surface water draining from watershed was

measuredmeasured

Removal of vegetation caused a six-fold Removal of vegetation caused a six-fold

increase in the calcium content of the runoff increase in the calcium content of the runoff

waterwater

Hubbard Brook ExperimentHubbard Brook Experiment

losses fromdisturbed watershed

time ofdeforestation

losses fromundisturbed watershed

Figure 48.15Page 877

Carbon CycleCarbon Cycle

Carbon moves through the atmosphere Carbon moves through the atmosphere

and food webs on its way to and from and food webs on its way to and from

the ocean, sediments, and rocksthe ocean, sediments, and rocks

Sediments and rocks are the main Sediments and rocks are the main

reservoirreservoir

Figure 48.16 Page 878

diffusion between atmosphere and ocean

bicarbonate and carbonate in ocean water

marine food webs

marine sediments

combustion of fossil fuels

incorporation into sediments

death, sedimentation uplifting

sedimentation

photosynthesis aerobic respiration

Carbon Cycle - MarineCarbon Cycle - Marine

Carbon Cycle - LandCarbon Cycle - Land

photosynthesis aerobic respirationterrestrial

rocks

soil water

land food webs

atmosphere

peat, fossil fuels

combustion of wood

sedimentation

volcanic action

death, burial, compaction over geologic time

leaching, runoff

weathering

combustion of fossil fuels

Figure 48.16 Page 878

Carbon in the OceansCarbon in the Oceans

Most carbon in the ocean is dissolved Most carbon in the ocean is dissolved carbonate and bicarbonatecarbonate and bicarbonate

Ocean currents carry dissolved carbon Ocean currents carry dissolved carbon

Carbon in AtmosphereCarbon in Atmosphere

Atmospheric carbon is mainly carbon Atmospheric carbon is mainly carbon dioxidedioxide

Carbon dioxide is added to atmosphereCarbon dioxide is added to atmosphere Aerobic respiration, volcanic action, burning Aerobic respiration, volcanic action, burning

fossil fuels fossil fuels

Removed by photosynthesisRemoved by photosynthesis

Greenhouse EffectGreenhouse Effect

Greenhouse gases impede the escape Greenhouse gases impede the escape

of heat from Earth’s surfaceof heat from Earth’s surface

Figure 48.18, Page 880

Global WarmingGlobal Warming

Long-term increase in the temperature of Long-term increase in the temperature of

Earth’s lower atmosphereEarth’s lower atmosphere

Figure 48.19, Page 881

Carbon Dioxide IncreaseCarbon Dioxide Increase

Carbon dioxide levels fluctuate seasonally Carbon dioxide levels fluctuate seasonally

The average level is steadily increasingThe average level is steadily increasing

Burning of fossil fuels and deforestation are Burning of fossil fuels and deforestation are

contributing to the increasecontributing to the increase

Other Greenhouse GasesOther Greenhouse Gases

CFCs - synthetic gases used in plastics and in CFCs - synthetic gases used in plastics and in

refrigerationrefrigeration

Methane - produced by termites and bacteriaMethane - produced by termites and bacteria

Nitrous oxide - released by bacteria, fertilizers, Nitrous oxide - released by bacteria, fertilizers,

and animal wastesand animal wastes

Nitrogen CycleNitrogen Cycle

Nitrogen is used in amino acids and nucleic Nitrogen is used in amino acids and nucleic

acidsacids

Main reservoir is nitrogen gas in the Main reservoir is nitrogen gas in the

atmosphereatmosphere

Nitrogen CycleNitrogen Cyclegaseous nitrogen (N2)

in atmosphere

NO3-

in soil

nitrogen fixationby industry

fertilizers

NH3-,NH4

+

in soil

1. Nitrification leaching

uptake by autotrophs

excretion, death, decomposition

uptake by autotrophs

nitrogen fixation

leaching

ammonification 2. Nitrification

dentrification nitrogenous

wastes, remains

NO2-

in soil

food webs on land

Figure 48.21Page 882

Nitrogen FixationNitrogen Fixation

Plants cannot use nitrogen gasPlants cannot use nitrogen gas

Nitrogen-fixing bacteria convert Nitrogen-fixing bacteria convert

nitrogen gas into ammonia (NHnitrogen gas into ammonia (NH33))

Ammonia and ammonium can be taken Ammonia and ammonium can be taken

up by plantsup by plants

Ammonification & NitrificationAmmonification & Nitrification

Bacteria and fungi carry out ammonificationBacteria and fungi carry out ammonification

conversion of nitrogenous wastes to ammoniaconversion of nitrogenous wastes to ammonia

Nitrifying bacteria convert ammonium to Nitrifying bacteria convert ammonium to

nitrites and nitratesnitrites and nitrates

Nitrogen LossNitrogen Loss

Nitrogen is often a limiting factor in Nitrogen is often a limiting factor in

ecosystemsecosystems

Nitrogen is lost from soils via leaching and Nitrogen is lost from soils via leaching and

runoff runoff

Denitrifying bacteria convert nitrates and Denitrifying bacteria convert nitrates and

nitrites to nitrogen gasnitrites to nitrogen gas

Human EffectsHuman Effects

Humans increase rate of nitrogen loss by Humans increase rate of nitrogen loss by clearing forests and grasslandsclearing forests and grasslands

Humans increase nitrogen in water and air by Humans increase nitrogen in water and air by using fertilizers and by burning fossil fuelsusing fertilizers and by burning fossil fuels

Too much or too little nitrogen can Too much or too little nitrogen can compromise plant healthcompromise plant health

Phosphorus CyclePhosphorus Cycle

Phosphorus is part of phospholipids and Phosphorus is part of phospholipids and

all nucleotidesall nucleotides

It is the most prevalent limiting factor in It is the most prevalent limiting factor in

ecosystems ecosystems

Main reservoir is Earth’s crust; no Main reservoir is Earth’s crust; no

gaseous phasegaseous phase

Phosphorus CyclePhosphorus Cycle

GUANO

FERTILIZER

TERRESTRIAL ROCKS

LAND FOOD WEBS

DISSOLVED IN OCEAN

WATER

MARINE FOOD WEBS

MARINE SEDIMENTS

excretion

weathering

mining

agricultureuptake

by autotrophs

death, decomposition

sedimentationsettling

out leaching, runoff

weathering

uplifting

over geologic time

DISSOLVED IN SOILWATER,

LAKES, RIVERS

uptake by

autotrophs

death, decomposition

Figure 48.23, Page 884

Human EffectsHuman Effects

In tropical countries, clearing lands for In tropical countries, clearing lands for

agriculture may deplete phosphorus-poor agriculture may deplete phosphorus-poor

soilssoils

In developed countries, phosphorus runoff is In developed countries, phosphorus runoff is

causing eutrophication of waterwayscausing eutrophication of waterways