PowerLecture: Chapter 25 Ecology and Human Concerns

PowerLecture:PowerLecture:Chapter 25Chapter 25

Ecology and Ecology and Human ConcernsHuman Concerns

Learning ObjectivesLearning Objectives

Understand how materials and energy Understand how materials and energy enter, pass through, and exit an ecosystem. enter, pass through, and exit an ecosystem.

Describe how communities are organized, Describe how communities are organized, how they develop, and how they diversify.how they develop, and how they diversify.

Understand the various trophic roles and Understand the various trophic roles and levels.levels.

Diagram the principal biogeochemical Diagram the principal biogeochemical cycles.cycles.

Learn the language associated with the Learn the language associated with the study of population ecology. study of population ecology.

Learning Objectives (cont’d)Learning Objectives (cont’d)

Understand the factors that affect Understand the factors that affect population density, distribution, and change. population density, distribution, and change.

Understand the meaning of logistic growth.Understand the meaning of logistic growth. Know the problems associated with the Know the problems associated with the

growth of human populations. Tell which growth of human populations. Tell which factors have encouraged growth in some factors have encouraged growth in some cultures and limited growth in others.cultures and limited growth in others.

Understand the magnitude of pollution Understand the magnitude of pollution problems in the United States. problems in the United States.

Learning Objectives (cont’d)Learning Objectives (cont’d)

Examine the effects modern agricultural Examine the effects modern agricultural techniques have on different ecosystems. techniques have on different ecosystems.

Describe how our use of fossil fuels and Describe how our use of fossil fuels and nuclear energy affects ecosystems.nuclear energy affects ecosystems.

Impacts/IssuesImpacts/Issues

The Human TouchThe Human Touch

The Human TouchThe Human Touch

At one time as many as 15,000 At one time as many as 15,000 people lived on Easter Island. people lived on Easter Island.

The tiny island could not support The tiny island could not support this many people.this many people.

Crop yields declined; soil nutrients Crop yields declined; soil nutrients were depleted.were depleted.

Large statues were erected to Large statues were erected to appease the gods.appease the gods.

The population dwindled and The population dwindled and then disappeared as people then disappeared as people turned against each other.turned against each other.

Video: Easter IslandVideo: Easter Island

From ABC News, Environmental Science in the Headlines, 2005 DVD.From ABC News, Environmental Science in the Headlines, 2005 DVD.

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How Would You Vote?How Would You Vote?To conduct an instant in-class survey using a classroom response To conduct an instant in-class survey using a classroom response system, access the “Polls Clicker Questions” from the PowerLecture system, access the “Polls Clicker Questions” from the PowerLecture main menu. main menu.

Are you willing to pay extra for “green” Are you willing to pay extra for “green” products?products? a. Yes, I would be willing to pay more for a. Yes, I would be willing to pay more for

sustainable products.sustainable products. b. No, I would not be willing to pay more for b. No, I would not be willing to pay more for

“green” products.“green” products.

Section 1Section 1

Some Basic Principles Some Basic Principles

of Ecologyof Ecology

Some Basic Principles of Ecology Some Basic Principles of Ecology

The The biospherebiosphere encompasses the earth’s encompasses the earth’s crust, atmosphere, and waters that support crust, atmosphere, and waters that support life; a life; a biomebiome is one of the major realms of is one of the major realms of life, such as deserts or rain forests.life, such as deserts or rain forests.

Figure 25.1Figure 25.1

Animation: Major BiomesAnimation: Major Biomes

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Animation: Terrestrial BiomesAnimation: Terrestrial Biomes

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EcologyEcology is the study of the interactions of is the study of the interactions of organisms with one another and with the organisms with one another and with the physical environment.physical environment.

A A habitathabitat is the place where a species normally is the place where a species normally lives; it is characterized by distinctive physical lives; it is characterized by distinctive physical features and vegetation.features and vegetation.

Humans live in Humans live in disturbed habitatsdisturbed habitats, places we , places we have modified to suit our own purposes.have modified to suit our own purposes.

A A communitycommunity is the collection of all the is the collection of all the populations in a given habitat.populations in a given habitat.


The The nicheniche refers to a range of physical and refers to a range of physical and biological conditions under which a species can biological conditions under which a species can live and reproduce.live and reproduce.

• Specialist speciesSpecialist species have narrow niches. have narrow niches.• GeneralistsGeneralists have broad ranges of habitats and have broad ranges of habitats and

niches.niches.


An An ecosystemecosystem consists of one or more consists of one or more communities interacting with one another communities interacting with one another and with the physical environment.and with the physical environment.

Communities Communities

of organisms of organisms

make up the make up the

bioticbiotic, or , or

living, portions living, portions

of an of an

ecosystem.ecosystem.Figure 25.2Figure 25.2


SuccessionSuccession is the is the orderly progression of orderly progression of species changes that species changes that leads to a leads to a climax climax communitycommunity..

• In In primary successionprimary succession, , changes begin when changes begin when pioneer species colonize pioneer species colonize a barren habitat.a barren habitat.

• In In secondary secondary successionsuccession, a , a community reestablishes community reestablishes itself toward a climax itself toward a climax state after a disturbance.state after a disturbance.


Animation: Two Types of Animation: Two Types of Ecological SuccessionEcological Succession

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Animation: Levels of OrganizationAnimation: Levels of Organization

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Video: Frogs GaloreVideo: Frogs Galore

From ABC News, Biology in the Headlines, 2005 DVD.From ABC News, Biology in the Headlines, 2005 DVD.

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Section 2Section 2

Feeding Levels and Feeding Levels and Food WebsFood Webs

Feeding Levels and Food Webs Feeding Levels and Food Webs

Many ecosystems exist, but they are all Many ecosystems exist, but they are all similar in structure and function.similar in structure and function.

ProducersProducers ((autotrophsautotrophs)) capture sunlight capture sunlight energy and incorporate it into organic energy and incorporate it into organic compounds.compounds.

All other organisms in an ecosystem are All other organisms in an ecosystem are consumersconsumers ((heterotrophsheterotrophs)) that depend on that depend on energy stored in the tissues of producers.energy stored in the tissues of producers.

energyinputfrom sun

NutrientCycling

Producers

Consumers

energy lost (mainly heat)

Fig 25.4, p. 456


• HerbivoresHerbivores eat plants ( eat plants (primary consumersprimary consumers).).• CarnivoresCarnivores eat animals ( eat animals (secondarysecondary oror tertiary tertiary

consumersconsumers).).• OmnivoresOmnivores eat a variety of organisms. eat a variety of organisms.• DecomposersDecomposers include fungi, bacteria, and small include fungi, bacteria, and small

invertebrates that extract energy from the remains or invertebrates that extract energy from the remains or products of organisms.products of organisms.

Ecosystems require energy and nutrient input Ecosystems require energy and nutrient input to continue to function.to continue to function.

Energy is generally lost from the system as Energy is generally lost from the system as heat; some nutrients can also be lost.heat; some nutrients can also be lost.

Animation: Energy FlowAnimation: Energy Flow

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Animation: The Role of Organisms Animation: The Role of Organisms in an Ecosystemin an Ecosystem

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Energy moves through a series of Energy moves through a series of ecosystem feeding levels.ecosystem feeding levels.

TrophicTrophic levelslevels (feeding levels) represent a (feeding levels) represent a hierarchy of energy transfers.hierarchy of energy transfers.

Level 1 (closest to the energy source) consists Level 1 (closest to the energy source) consists of primary producers, level 2 is composed of of primary producers, level 2 is composed of herbivores, and levels 3 and above are herbivores, and levels 3 and above are carnivores.carnivores.

Decomposers and omnivores such as humans Decomposers and omnivores such as humans feed on organisms from all levels.feed on organisms from all levels.

Animation: Trophic Levels in a Simple Animation: Trophic Levels in a Simple Food ChainFood Chain

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Animation: Prairie Trophic LevelsAnimation: Prairie Trophic Levels

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Food chains and webs show who eats Food chains and webs show who eats whom.whom.

A linear sequence of who eats whom in an A linear sequence of who eats whom in an ecosystem is called a ecosystem is called a food chainfood chain; simple ; simple chains are rarely found in nature.chains are rarely found in nature.

Cross-connecting food chains make up Cross-connecting food chains make up food food webswebs in which the same food resource is often in which the same food resource is often part of more than one food chain.part of more than one food chain.

In-text Fig, p. 466

Marsh Hawk

Upland Sandpiper

Garter Snake

Cutworm

Plants

In-text Fig, p. 466

Marsh Hawk

Upland Sandpiper

Garter Snake

Cutworm

PlantsStepped Art

Animation: Categories of Food WebsAnimation: Categories of Food Webs

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Animation: Prairie Food WebAnimation: Prairie Food Web

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© 2007 Thomson Higher Education

FirstFeedingLevelPrimaryproducers

Higher Feeding LevelsA variety of carnivores, omnivores, and other consumers.Many feedat morethan one level allthe time, seasonally, or when an opportunity presents itself

Crow

UplandSandpiper

Garter Snake

Frog

Spider Weasel Badger Coyote

GroundSquirrel

Pocket GopherPrairie Vole

Clay-coloredSparrow

Earthworms, Insects(e.g.) Grasshoppers, Cutworms

Second FeedingLevelPrimary consumers (herbivores)

Grass

Marsh Hawk

Fig 25.5, p. 467

Animation: Rainforest Food WebAnimation: Rainforest Food Web

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Section 3Section 3

Energy Flow Energy Flow

through Ecosystemsthrough Ecosystems

Energy Flow through Ecosystems Energy Flow through Ecosystems

Producers capture and store energy.Producers capture and store energy. Primary productivityPrimary productivity is the total rate of is the total rate of

photosynthesis (trapping of energy) for the photosynthesis (trapping of energy) for the ecosystem during a specified interval.ecosystem during a specified interval.

How much energy is trapped depends on many How much energy is trapped depends on many factors. factors.

• The number of individual plants and the relative The number of individual plants and the relative balance between trapping energy and expending balance between trapping energy and expending energy to produce new plants.energy to produce new plants.

• Environmental factors such as availability of mineral Environmental factors such as availability of mineral nutrients, rain fall, and temperature.nutrients, rain fall, and temperature.

Earth’s Primary ProductivityEarth’s Primary Productivity



Consumers subtract energy from Consumers subtract energy from ecosystems.ecosystems.

An An ecological pyramidecological pyramid describes the energy describes the energy relationships in an ecosystem.relationships in an ecosystem.

• Primary producers form the base.Primary producers form the base.• Successive tiers of consumers are found above Successive tiers of consumers are found above

them.them.


Ecological pyramids can be of two basic types:Ecological pyramids can be of two basic types:• BiomassBiomass is the combined weight of all of an is the combined weight of all of an

ecosystem’s organisms at each level of the pyramid; ecosystem’s organisms at each level of the pyramid; a a biomass pyramidbiomass pyramid can be “right-side up,” with can be “right-side up,” with producers outnumbering consumers, or “upside-producers outnumbering consumers, or “upside-down,” which is the opposite.down,” which is the opposite.

• An An energy pyramidenergy pyramid reflects the trophic structure reflects the trophic structure more accurately because it is based on energy more accurately because it is based on energy losses at each level; energy pyramids are always losses at each level; energy pyramids are always “right-side up.”“right-side up.”

Figure 25.7aFigure 25.7a

5

decomposers(bacteria, crayfish)

1.5

11

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

Fig 25.7a, p.468

5

decomposers(bacteria, crayfish)

1.5

11

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

second-level consumers(fishes, invertebrates)

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

primary producers (algae, eelgrass, rooted plants)

809

Fig 25.7a, p.468

Stepped Art

Fig 25.7bFig 25.7b

top carnivores

carnivores

herbivores

producers

Decomposers =21

383

3,368

20,810

5,060

Section 4Section 4

Biogeochemical Cycles—Biogeochemical Cycles—

An OverviewAn Overview

Biogeochemical cyclesBiogeochemical cycles describe the describe the movement of nutrients from the movement of nutrients from the environment to organisms and then back to environment to organisms and then back to the environment that serves as a reservoir the environment that serves as a reservoir for them.for them.

Cycling is slowest through the reservoir.Cycling is slowest through the reservoir. The amount of nutrient being recycled through The amount of nutrient being recycled through

major ecosystems is greater than the amount major ecosystems is greater than the amount entering or leaving in a given year.entering or leaving in a given year.

Inputs to an ecosystem’s nutrient reserves are Inputs to an ecosystem’s nutrient reserves are by precipitation, metabolism, and rock by precipitation, metabolism, and rock weathering; outputs include losses by runoff.weathering; outputs include losses by runoff.

Biogeochemical CyclesBiogeochemical Cycles

geochemical cyclenutrient reservoirs in environment

fraction available to ecosystem

primary producers

consumers (herbivores, carnivores, parasites)

decomposers

Fig 25.8, p. 469

There are three categories of There are three categories of biogeochemical cycles:biogeochemical cycles:

In the In the global water cycleglobal water cycle, oxygen and , oxygen and hydrogen move as water molecules.hydrogen move as water molecules.

In the In the atmospheric cyclesatmospheric cycles, elements such as , elements such as carbon and nitrogen move in gaseous phase.carbon and nitrogen move in gaseous phase.

In In sedimentary cyclessedimentary cycles, solid, non-gaseous , solid, non-gaseous nutrients move from land to the seafloor and nutrients move from land to the seafloor and back to land through geological uplifting; this is back to land through geological uplifting; this is a very slow cycle.a very slow cycle.

Biogeochemical CyclesBiogeochemical Cycles

Section 5Section 5

The Water CycleThe Water Cycle

The Water Cycle The Water Cycle

The The hydrologic cyclehydrologic cycle (water cycle) (water cycle) encompasses water in the oceans, encompasses water in the oceans, atmosphere, and land.atmosphere, and land.

The ocean serves as the main water reservoir.The ocean serves as the main water reservoir. Evaporation moves water into the lower Evaporation moves water into the lower

atmosphere where it returns to Earth as atmosphere where it returns to Earth as precipitation.precipitation.

Animation: Hydrologic CycleAnimation: Hydrologic Cycle

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Fig 25.9, p. 470

atmosphere

ocean land

evaporationfrom ocean

425,000

precipitationinto ocean

385,000

precipitationonto land111,000

evaporation fromland plants

(transpiration)71,000

surface andgroundwater flow

40,000

wind-driven water vapor40,000

The Water Cycle The Water Cycle

Water moves nutrients in or out of Water moves nutrients in or out of ecosystems.ecosystems.

A A watershedwatershed funnels rain or snow into a single funnels rain or snow into a single river.river.

Plants absorb nutrients to prevent their loss by Plants absorb nutrients to prevent their loss by leaching.leaching.

Section 6Section 6

Cycling Chemicals from Cycling Chemicals from the Earth’s Crustthe Earth’s Crust

There are two phases in the There are two phases in the phosphorus phosphorus cyclecycle::

In the geochemical phase, phosphorus moves In the geochemical phase, phosphorus moves from land to sediments in the seas and back to from land to sediments in the seas and back to the land over long periods of time.the land over long periods of time.

In the much more rapid ecosystem phase, In the much more rapid ecosystem phase, plants take up the phosphorus from the soil; it is plants take up the phosphorus from the soil; it is then transferred to herbivores and carnivores, then transferred to herbivores and carnivores, which excrete it in wastes and their own which excrete it in wastes and their own decomposing bodies thus returning the decomposing bodies thus returning the phosphorus to plants.phosphorus to plants.

Cycling Chemicals from the Earth’s Crust Cycling Chemicals from the Earth’s Crust

Excessive phosphorus compounds in runoff Excessive phosphorus compounds in runoff water can lead to water can lead to eutrophicationeutrophication of lakes of lakes and streams, characterized by explosive and streams, characterized by explosive growth of algae and weeds. growth of algae and weeds.

Cycling Chemicals from the Earth’s Crust Cycling Chemicals from the Earth’s Crust

Animation: Phosphorus CycleAnimation: Phosphorus Cycle

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Guano

Fertilizer

Rocks

LandFood Webs

Dissolved in Ocean Water

Marine Food Webs

Marine Sediments

excretion

weathering

mining

agricultureuptake by autotrophs

death, decomposition

sedimentation settling out leaching, runoff

weathering

uplifting overgeologic time

Dissolved in Soil Water,

Lakes, Rivers

uptake by autotrophs

death, decomposition

Fig 25.10, p. 471

Section 7Section 7

The Carbon CycleThe Carbon Cycle

The Carbon Cycle The Carbon Cycle

In the In the carbon cyclecarbon cycle, sediments and rocks , sediments and rocks hold most of the carbon; carbon moves also hold most of the carbon; carbon moves also through the oceans, soil, atmosphere, and through the oceans, soil, atmosphere, and biomass.biomass.

Carbon enters the atmosphere as COCarbon enters the atmosphere as CO22

produced by aerobic respiration, fossil-fuel produced by aerobic respiration, fossil-fuel burning, and volcanic eruptions.burning, and volcanic eruptions.


Carbon in the ocean occurs as bicarbonate and Carbon in the ocean occurs as bicarbonate and carbonate; carbon dioxide in the ocean is carbonate; carbon dioxide in the ocean is carried to deep storage reservoirs on the carried to deep storage reservoirs on the seafloor.seafloor.


Fig 25.12, p. 473

Cold, salty, deep current

The Carbon Cycle The Carbon Cycle

Carbon is removed from the atmosphere and Carbon is removed from the atmosphere and the ocean by photosynthesizers and shelled the ocean by photosynthesizers and shelled organisms; carbon is held for different periods organisms; carbon is held for different periods of time in different ecosystems.of time in different ecosystems.

Decomposition of buried carbon compounds Decomposition of buried carbon compounds millions of years ago caused the formation of millions of years ago caused the formation of fossil fuels (natural gas, petroleum, and coal).fossil fuels (natural gas, petroleum, and coal).

Burning of fossil fuels puts extra amounts of Burning of fossil fuels puts extra amounts of carbon dioxide into the atmosphere, an carbon dioxide into the atmosphere, an occurrence that may lead to global warming.occurrence that may lead to global warming.

Animation: Carbon CycleAnimation: Carbon Cycle

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diffusion between atmosphere and ocean

Bicarbonate and Carbonate

Dissolved in Ocean Water

Marine Food Webs, producers consumers,

decomposers

Marine Sediments, Including Formations with Fossil Fuels

combustion of fossil fuels

incorporationinto sediments

death, sedimentation

uplifting over geologic time

sedimentation

photosynthesis aerobic respiration

Fig. 25.11a, p. 472

leaching,runoff

Soil Water(dissolved carbon)

TerrestrialRocks

©2007 Thomson Higher Education

photosynthesisaerobic

respiration

Land Food Websproducers, consumers,

decomposers

Atmosphere

Peat, Fossil Fuels

combustion of wood (for

cleaning land; or for fuel)

sedimentation

death, burial,compactionover geologic time

combustion of fossil fuels

Fig. 25.11b, p. 473

Section 8Section 8

Global WarmingGlobal Warming

Global Warming Global Warming

The greenhouse effect.The greenhouse effect. Molecules of gases such as carbon dioxide, Molecules of gases such as carbon dioxide,

water, ozone, and others act like a pane of water, ozone, and others act like a pane of glass over the surface of the Earth.glass over the surface of the Earth.


Animation: Greenhouse GasesAnimation: Greenhouse Gases

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Carbon dioxide

Fig 25.14a2, p. 475

19951960 1965 1970 1975 1980

Time (years)

380

300

360

340

320Co

nce

ntr

atio

n (

par

ts p

er b

illi

on

)

1985 1990


Fig. 25.14b, p. 475

CFCs

19981976 1980 1985 1990 1995

Time (years)

1200

400

1000

800

600

Co

nce

ntr

atio

n (

par

ts p

er t

rill

ion

)

200


Fig. 25.14c, p. 475

Methane

1976 19981980 1985 1990 1995

Time (years)

1.80

1.40

1.70

1.60

1.50

Co

nce

ntr

atio

n (

par

ts p

er b

illi

on

)


Co

nce

ntr

atio

n (

par

ts p

er b

illi

on

)320

310

300

290

280

270

2601976 1980 1985 1990 1995 1998

Time (years)

Nitrous oxide (N2O)

Fig. 25.14d, p. 475


Wavelengths of visible light easily pass Wavelengths of visible light easily pass downward to Earth, but infrared wavelengths—downward to Earth, but infrared wavelengths—heat—are impeded from passing back into heat—are impeded from passing back into space.space.

The warming of the lower atmosphere is called The warming of the lower atmosphere is called the the greenhouse effectgreenhouse effect..


Fig 25.13, p. 474

Rays of sunlightpenetrate the loweratmosphere and warm the earth’s surface.

a Surface radiates heat (infrared wavelengths) to the lower atmosphere. Some heat escapes into space. But greenhouse gases and water vapor absorb some infrared energy and radiate a portion of it back toward earth.

b Increased concentrations of greenhouse gases trap more heat near Earth’s surface. Sea surface temperature rises, more water evaporates into the atmosphere, and Earth’s surface temperature rises.

c

Animation: Greenhouse EffectAnimation: Greenhouse Effect

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Global warming.Global warming. Concentrations of greenhouse gases are Concentrations of greenhouse gases are

increasing and may be at the highest levels increasing and may be at the highest levels they have been at for 420,000 to 20 million they have been at for 420,000 to 20 million years.years.

The result is a long-term rise in temperature—The result is a long-term rise in temperature—globalglobal warmingwarming; irreversible climate changes ; irreversible climate changes are already underway, such as melting of the are already underway, such as melting of the polar ice caps and retreating of glaciers.polar ice caps and retreating of glaciers.

Animation: Carbon Dioxide Animation: Carbon Dioxide and Temperatureand Temperature

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Global TemperatureGlobal Temperature


Video: Kyoto ProtocolVideo: Kyoto Protocol

This video clip is available in CNN Today This video clip is available in CNN Today Videos for Environmental Science, 2004, Videos for Environmental Science, 2004, Volume VII. Instructors, contact your local Volume VII. Instructors, contact your local sales representative to order this volume, sales representative to order this volume, while supplies last.while supplies last.

Section 9Section 9

The Nitrogen CycleThe Nitrogen Cycle

The Nitrogen Cycle The Nitrogen Cycle

Gaseous nitrogen (NGaseous nitrogen (N22) makes up about 80% ) makes up about 80%

of the atmosphere, which is the largest of the atmosphere, which is the largest reservoir; this form of nitrogen can only be reservoir; this form of nitrogen can only be brought into the brought into the nitrogen cyclenitrogen cycle by certain by certain species of bacteria.species of bacteria.

In In nitrogen fixationnitrogen fixation, bacteria convert N, bacteria convert N22 to to

ammonia, which is then used in the synthesis of ammonia, which is then used in the synthesis of proteins and nucleic acids to be assimilated into proteins and nucleic acids to be assimilated into plant, then animal, tissues.plant, then animal, tissues.

The Nitrogen Cycle The Nitrogen Cycle

Decomposition of dead nitrogen fixers releases Decomposition of dead nitrogen fixers releases nitrogen-containing compounds.nitrogen-containing compounds.

NitrificationNitrification is a type of chemosynthesis where is a type of chemosynthesis where ammonia and ammonium ions are converted to ammonia and ammonium ions are converted to nitrite; nitrite is turned to nitrates by bacteria for nitrite; nitrite is turned to nitrates by bacteria for uptake by plants.uptake by plants.

DenitrificationDenitrification is the release of nitrogen gas to is the release of nitrogen gas to the atmosphere by the action of bacteria.the atmosphere by the action of bacteria.

Nitrogen can be lost from ecosystems Nitrogen can be lost from ecosystems through leaching.through leaching.

Animation: Nitrogen CycleAnimation: Nitrogen Cycle

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Nitrate

in Soil

Nitrogen Fixationby industry for agriculture

Fertilizers

Food Webs on Land

Ammonia, Ammonium

in Soil

Nitrificationloss by

leaching


excretion, death, decomposition


Nitrogen Fixation

by bacteria

Ammonificationbacteria, fungi convert residues to NH3; this dissolves to form NH4

Nitrification

Loss byDenitrification

Nitrogen gasin Atmosphere

Fig 25.16, p. 476

Nitrate

in Soil

Consumers

loss by leaching

Nitrogen-rich wastes,Remains in soil

Section 10Section 10

Biological MagnificationBiological Magnification

Biological Magnification Biological Magnification

DDT is a synthetic organic pesticide that DDT is a synthetic organic pesticide that was first used during World War II in the was first used during World War II in the fight against malaria and typhus; after the fight against malaria and typhus; after the war it continued to be used as a pesticide to war it continued to be used as a pesticide to control agricultural and forest pests.control agricultural and forest pests.

DDT is insoluble in water, but it is fat soluble.DDT is insoluble in water, but it is fat soluble. Vapor forms and small particles in water can Vapor forms and small particles in water can

carry DDT through an environment; from the carry DDT through an environment; from the environment it can be absorbed into tissues.environment it can be absorbed into tissues.


Biological magnificationBiological magnification describes the describes the increased concentration of slowly increased concentration of slowly degradable substances in organisms as it is degradable substances in organisms as it is passed upward in a food chain.passed upward in a food chain.

Each organism in a chain essentially assumes Each organism in a chain essentially assumes the absorbed DDT in each organism it feeds on the absorbed DDT in each organism it feeds on lower in the chain.lower in the chain.

With DDT, organisms at the very top of the food With DDT, organisms at the very top of the food chain, such as bald eagles and other predatory chain, such as bald eagles and other predatory birds, suffered the most and some were pushed birds, suffered the most and some were pushed almost to extinction.almost to extinction.


DDT is banned in the US, but this is not true DDT is banned in the US, but this is not true outside of the US.outside of the US.


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 (Strongylura 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

Fig 25.17a, p. 477

Data for a Long Island, NY, estuary in 1967

Animation: Pesticide ExamplesAnimation: Pesticide Examples

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Human Human Population GrowthPopulation Growth

Human Population Growth Human Population Growth

The human population is growing rapidly.The human population is growing rapidly. The world population reached the 6.3 billion The world population reached the 6.3 billion

mark in 2004.mark in 2004.• It took 2.5 million years for the world’s human It took 2.5 million years for the world’s human

population to reach 1 billion.population to reach 1 billion.• It took less than 200 years for it to reach 6 billion.It took less than 200 years for it to reach 6 billion.

The growth rate is determined mainly by the The growth rate is determined mainly by the balance between births and deaths.balance between births and deaths.

• The The total fertility ratetotal fertility rate (TFR) is the average number (TFR) is the average number of children born to a woman.of children born to a woman.

• Many developed countries have a TFR at or below Many developed countries have a TFR at or below 2.1 (replacement rate), but some developing 2.1 (replacement rate), but some developing countries have a TFR two or three times this rate.countries have a TFR two or three times this rate.


Fig. 25.19, p. 478

14,000 12,000 10,000 8,000 6,000 4,000 2,000BC AD

2,000

1

2

3

4

5

6

beginning ofindustrial,scientificrevolutions

agriculturally basedurban societies

domestication of plants, animals 9000B.C. (about 11,000 years ago)

Estimated size by10,000 years ago 5 million

By 1904 1 billionBy 1927 2 billionBy 1960 3 billionBy 1974 4 billionBy 1987 5 billionBy 1999 6 billionProjected for 2050 8.9 billion

Animation: Exponential GrowthAnimation: Exponential Growth

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Population statistics help predict growth.Population statistics help predict growth. DemographicsDemographics influence a population’s growth influence a population’s growth

and impact on ecosystems.and impact on ecosystems.• Population sizePopulation size is the number of individuals in the is the number of individuals in the

population’s gene pool.population’s gene pool.• Population densityPopulation density is the number of individuals per is the number of individuals per

unit of area or volume.unit of area or volume.• Population distributionPopulation distribution refers to the general refers to the general

pattern in which the population members are pattern in which the population members are distributed, such as clustering in towns or cities.distributed, such as clustering in towns or cities.


population in 2003

population under age 15

total fertility rate

infant mortality rate

Fig. 25.20a, p. 479

292 million

134 million

351 million

206 million211 million

21%30%

44%

13%6%

3%

life expectancy

per capita income in 2001

population in 2050 (projected)

population above age 65

177 million

2.02.2

5.8

6.9 per 1,000 births33 per 1,000 births

75 per 1,000 births

77 years69 years

52 years

$34,280$7,070

$800

Gold: U.S.Gold: U.S.

Brown: BrazilBrown: Brazil

Ivory: NigeriaIvory: Nigeria

Animation: Current and Projected Animation: Current and Projected Population Sizes by RegionPopulation Sizes by Region

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Age structureAge structure defines the relative proportions defines the relative proportions of individuals of each age.of individuals of each age.

• The three categories are: prereproductive, The three categories are: prereproductive, reproductive, and postreproductive.reproductive, and postreproductive.

• The The reproductive basereproductive base (prereproductive and (prereproductive and reproductive members) for a human population will reproductive members) for a human population will determine the future growth rate of a population.determine the future growth rate of a population.


Fig 25.21, p. 479

UNITED STATES INDIA

Animation: Age Structure DiagramsAnimation: Age Structure Diagrams

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Animation: U.S. Age StructureAnimation: U.S. Age Structure

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Nature’s Controls on Nature’s Controls on Population GrowthPopulation Growth

Nature’s Controls on Population Growth Nature’s Controls on Population Growth

The human population has been growing The human population has been growing exponentially since the mid-1700s.exponentially since the mid-1700s.

There is a limit on how many people the There is a limit on how many people the Earth can sustain.Earth can sustain.

The The biotic potentialbiotic potential of a population is its of a population is its maximum rate of increase under ideal—maximum rate of increase under ideal—nonlimiting—conditions.nonlimiting—conditions.

Limiting factors on population growth could Limiting factors on population growth could include any essential resource that is in short include any essential resource that is in short supply such as food, water, or living space; supply such as food, water, or living space; predation and pathogens can also be limiting.predation and pathogens can also be limiting.


The number of individuals that can be The number of individuals that can be sustained by the resources in a given area is sustained by the resources in a given area is the the carrying capacitycarrying capacity..

The carrying capacity can vary over time and is The carrying capacity can vary over time and is expressed graphically in the S-shaped curve expressed graphically in the S-shaped curve pattern called pattern called logistic growthlogistic growth..


new carrying capacity

Fig 25.22, p. 480

initial carrying capacity

Nu

mb

er o

f in

div

idu

als

TIME A B C D E

Animation: Demographic Transition ModelAnimation: Demographic Transition Model

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Some natural population controls are Some natural population controls are related to population density.related to population density.

Density-dependent controlsDensity-dependent controls (such as (such as diseases) are limiting factors that exert their diseases) are limiting factors that exert their effects with respect to the number of individuals effects with respect to the number of individuals present.present.

Density-independent controlsDensity-independent controls, such as , such as natural disasters, tend to increase the death natural disasters, tend to increase the death rate without respect to the number of rate without respect to the number of individuals present.individuals present.

Video: People ExplosionVideo: People Explosion

From ABC News, Human Biology in the Headlines, 2006 DVD.From ABC News, Human Biology in the Headlines, 2006 DVD.

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Assaults on Our Air Assaults on Our Air


PollutantsPollutants are substances that adversely are substances that adversely affect health, activities, or survival of a affect health, activities, or survival of a population.population.

Air pollutants include oxides of carbon, sulfur, Air pollutants include oxides of carbon, sulfur, and nitrogen as well as CFCs.and nitrogen as well as CFCs.

Over 700,000 metric tons of pollutants are Over 700,000 metric tons of pollutants are released into the atmosphere every day in the released into the atmosphere every day in the United States alone.United States alone.


Pollutants may be trapped in the atmosphere to Pollutants may be trapped in the atmosphere to produce two types of smog:produce two types of smog:

• Industrial smogIndustrial smog is gray air found in industrial cities is gray air found in industrial cities that burn fossil fuels.that burn fossil fuels.

• Photochemical smogPhotochemical smog is brown air found in large is brown air found in large cities in warm climates; for example, gases from car cities in warm climates; for example, gases from car exhaust.exhaust.

Burning of fossil fuels produces oxide particles Burning of fossil fuels produces oxide particles that can fall to the earth as that can fall to the earth as acid rainacid rain..

Animation: Thermal Inversion and SmogAnimation: Thermal Inversion and Smog

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Animation: Formation of Animation: Formation of Photochemical SmogPhotochemical Smog

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Animation: Acid DepositionAnimation: Acid Deposition

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Animation: Effect of Air Pollution Animation: Effect of Air Pollution in Forestsin Forests

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The ozone layer has been damaged.The ozone layer has been damaged. OzoneOzone (O (O33) in the lower stratosphere absorbs ) in the lower stratosphere absorbs

most of the ultraviolet radiation from the sun.most of the ultraviolet radiation from the sun.• Ozone thinningOzone thinning has produced an ozone hole over has produced an ozone hole over

Antarctica; in 2001 an ozone hole appeared over the Antarctica; in 2001 an ozone hole appeared over the Arctic. Arctic.

• Chlorofluorocarbons (CFCs) seem to be the cause—Chlorofluorocarbons (CFCs) seem to be the cause—one chlorine atom can destroy 10,000 molecules of one chlorine atom can destroy 10,000 molecules of ozone.ozone.


While most CFC production is being phased While most CFC production is being phased out, it will take 100 to 200 years for the ozone out, it will take 100 to 200 years for the ozone layer to fully recover once all production and layer to fully recover once all production and use ceases.use ceases.


Animation: How CFCs Destroy OzoneAnimation: How CFCs Destroy Ozone

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Video: Clean Air ActVideo: Clean Air Act


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Water, Wastes, and Water, Wastes, and Other ProblemsOther Problems

Water, Wastes, and Other Problems Water, Wastes, and Other Problems

Problems with water are serious.Problems with water are serious. Three out of four humans do not have enough Three out of four humans do not have enough

clean water to meet basic needs.clean water to meet basic needs. About one third of all food is raised on irrigated About one third of all food is raised on irrigated

land, leading to salt buildup (land, leading to salt buildup (salinizationsalinization) and ) and depletion of ground water systems.depletion of ground water systems.



Humans waste limited water supplies and Humans waste limited water supplies and pollute much of the remaining water through pollute much of the remaining water through agricultural and industrial runoff; even garbage agricultural and industrial runoff; even garbage and debris is dumped into our waterways.and debris is dumped into our waterways.

Animation: Stream PollutionAnimation: Stream Pollution

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Animation: Threats to AquifersAnimation: Threats to Aquifers

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Where will we put solid wastes and produce Where will we put solid wastes and produce food?food?

Finding enough space to bury our wastes is Finding enough space to bury our wastes is becoming a problem, and the dump sites can becoming a problem, and the dump sites can leak toxic materials into the soil and water.leak toxic materials into the soil and water.

Almost one quarter of all the land on Earth is Almost one quarter of all the land on Earth is used for agriculture.used for agriculture.

• The green revolution has increased crop yields but The green revolution has increased crop yields but uses many times more energy and mineral uses many times more energy and mineral resources.resources.

• Large-scale Large-scale desertificationdesertification is caused by is caused by overgrazing on marginal lands.overgrazing on marginal lands.


Deforestation has global repercussions.Deforestation has global repercussions. DeforestationDeforestation, the removal of all trees from , the removal of all trees from

large tracts of land, can reduce fertility, change large tracts of land, can reduce fertility, change rainfall patterns, increase temperatures, and rainfall patterns, increase temperatures, and increase carbon dioxide levels.increase carbon dioxide levels.


Clearing large tracts of tropical forests may Clearing large tracts of tropical forests may have global repercussions due to leaching and have global repercussions due to leaching and shifting rates of evaporation and sunlight shifting rates of evaporation and sunlight penetration.penetration.


Animation: Effects of DeforestationAnimation: Effects of Deforestation

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Video: Desertification in ChinaVideo: Desertification in China


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Concerns about EnergyConcerns about Energy

Concerns about Energy Concerns about Energy

The Earth has abundant energy, but the The Earth has abundant energy, but the netnet amount of energy left after subtracting the amount of energy left after subtracting the energy it costs to find, process, and deliver energy it costs to find, process, and deliver this energy is relatively small.this energy is relatively small.

Some forms of energy are renewable, such as Some forms of energy are renewable, such as solar energy; coal and petroleum are examples solar energy; coal and petroleum are examples of non-renewable energy.of non-renewable energy.

Figure 25.26aFigure 25.26a


People in developed countries use far more People in developed countries use far more energy per person than those in developing energy per person than those in developing countries.countries.

Figure 25.26bFigure 25.26b

Animation: Energy UseAnimation: Energy Use

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Fossil fuels are going fast.Fossil fuels are going fast. Fossil fuelsFossil fuels include oil, coal, and natural gas; include oil, coal, and natural gas;

these sources represent the fossilized remains these sources represent the fossilized remains of ancient forests and organisms.of ancient forests and organisms.

Petroleum and natural gas reserves may be Petroleum and natural gas reserves may be depleted during this century.depleted during this century.

Extraction and use of abundant reserves of coal Extraction and use of abundant reserves of coal are not environmentally attractive.are not environmentally attractive.


Can other energy sources meet the need?Can other energy sources meet the need? Nuclear power can produce electricity at Nuclear power can produce electricity at

relatively low cost, but there are risks.relatively low cost, but there are risks.• Meltdowns may release large amounts of Meltdowns may release large amounts of

radioactivity to the environment.radioactivity to the environment.• Waste is so radioactive that it must be isolated for Waste is so radioactive that it must be isolated for

10,000 years.10,000 years. Solar energy can be converted to the Solar energy can be converted to the

mechanical energy of wind to run turbines; mechanical energy of wind to run turbines; solar cells could be used to generate electricity solar cells could be used to generate electricity for producing hydrogen gas. for producing hydrogen gas.


Hybrid cars are currently available, which work Hybrid cars are currently available, which work on a combination of gasoline and the electricity on a combination of gasoline and the electricity from batteries.from batteries.

Fusion power has potential, but many obstacles Fusion power has potential, but many obstacles make the technology a distant possibility.make the technology a distant possibility.

Video: Nuclear EnergyVideo: Nuclear Energy


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Loss of BiodiversityLoss of Biodiversity

Loss of Biodiversity Loss of Biodiversity

Humans have become a major factor in the Humans have become a major factor in the premature extinction of more and more premature extinction of more and more species.species.

Extinction is irreversible and greatly decreases Extinction is irreversible and greatly decreases biodiversity.biodiversity.

Speciation cannot balance rapid extinction.Speciation cannot balance rapid extinction.

Animation: Humans Affect BiodiversityAnimation: Humans Affect Biodiversity

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Animation: Biodiversity Hot SpotsAnimation: Biodiversity Hot Spots

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Tropical deforestation is the greatest source Tropical deforestation is the greatest source of extinction of species, followed closely by of extinction of species, followed closely by destruction of coral reefs.destruction of coral reefs.

Loss of plant diversity directly hurts consumers Loss of plant diversity directly hurts consumers by removing an important part of every food by removing an important part of every food chain; plant loss also affects our sources of chain; plant loss also affects our sources of natural medicines.natural medicines.

The underlying causes of such destruction are The underlying causes of such destruction are human population growth and poor economic human population growth and poor economic policies.policies.

Animation: Habitat Loss Animation: Habitat Loss and Fragmentationand Fragmentation

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16201850

1850 (pocket only)

1990

Fig 25.29, p. 487

Animation: Resource Depletion Animation: Resource Depletion and Degradationand Degradation

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To end the trend, we must collectively fight To end the trend, we must collectively fight to reduce deforestation, global warming, to reduce deforestation, global warming, ozone depletion, and poverty.ozone depletion, and poverty.

Figures 25.27 and 25.28Figures 25.27 and 25.28

Documents

PowerLecture: Chapter 25 Ecology and Human Concerns