Principles Of EcologyPrinciples Of Ecology

I.I. How Populations How Populations GrowGrow

A.A. What Is a Population?What Is a Population? PopulationPopulation:: a group of organisms of a group of organisms of

the same species that live in a specific the same species that live in a specific geographical areas and interbreedgeographical areas and interbreed

Example: Example:

Human PopulationHuman Population

Escherichia Coli (bacteria)Escherichia Coli (bacteria)

Populations grow because Populations grow because individuals tend to have multiple individuals tend to have multiple offspring over their lifetime.offspring over their lifetime.

Limited resources in an environment Limited resources in an environment limit the growth of a population.limit the growth of a population.

DemographyDemography: statistical study of : statistical study of all populationsall populations

Three key features of populationsThree key features of populations::1.1. Population sizePopulation size

The number of individuals in a populationThe number of individuals in a population Can affect the population’s ability to surviveCan affect the population’s ability to survive Very small populations are among those most Very small populations are among those most

likely to become extinctlikely to become extinct Random events or natural disturbances, such Random events or natural disturbances, such

as a fire or flood, endanger small populations as a fire or flood, endanger small populations more than they endanger larger populationsmore than they endanger larger populations

Small populations tend to experience more Small populations tend to experience more inbreeding (breeding with relatives)inbreeding (breeding with relatives)

Inbreeding produces a more genetically Inbreeding produces a more genetically uniform population and is therefore likely to uniform population and is therefore likely to reduce the population’s fitnessreduce the population’s fitness

2.2. Population densityPopulation density The number of individuals that live in a The number of individuals that live in a

given areagiven area If the individuals of a population are few If the individuals of a population are few

and the area is large enough to let them and the area is large enough to let them spread out, the individuals may seldom spread out, the individuals may seldom encounter each other, making encounter each other, making reproduction rarereproduction rare

3.3. DispersionDispersion The way the individuals of the population The way the individuals of the population

are arranged in spaceare arranged in space There are three possible patterns of There are three possible patterns of

dispersion in a population:dispersion in a population: Random Distribution:Random Distribution: The location of each The location of each

individual is self-determined or determined by individual is self-determined or determined by chancechance

Even Distribution:Even Distribution: The individuals are The individuals are located at regular intervalslocated at regular intervals

Clumped Distribution: Clumped Distribution: The individuals are The individuals are bunched together in clustersbunched together in clusters

Each of these patterns reflects the Each of these patterns reflects the interactions between the population and its interactions between the population and its environmentenvironment

Patterns of DispersionPatterns of Dispersion

B.B. Modeling Population Modeling Population GrowthGrowth

Population ModelPopulation Model:: Hypothetical Hypothetical population that attempts to exhibit the population that attempts to exhibit the key characteristics of a real populationkey characteristics of a real population

By making a change in the model and By making a change in the model and observing the outcome, demographers observing the outcome, demographers can predict what might occur in a real can predict what might occur in a real population.population.

Growth Rate Growth Rate A population grows when more individuals A population grows when more individuals

are born than die in a given period.are born than die in a given period. A simple population model describes the A simple population model describes the

rate of population growth as the difference rate of population growth as the difference between the birthrate and death ratebetween the birthrate and death rate

birthrate – death rate = rate of growthbirthrate – death rate = rate of growth For human populations, birth and death For human populations, birth and death

rates are usually expressed as the number rates are usually expressed as the number of births and deaths per thousand people of births and deaths per thousand people per yearper year

Growth Rate and Population SizeGrowth Rate and Population Size Exponential growth curve:Exponential growth curve: A curve in A curve in

which the rate of population growth stays which the rate of population growth stays the same, as a result the population size the same, as a result the population size increases steadily.increases steadily.

Populations do not usually grow unchecked, Populations do not usually grow unchecked, since growth is limited by predators, since growth is limited by predators, disease, and the availability of resources.disease, and the availability of resources.

The population size that an environment The population size that an environment can sustain is called thecan sustain is called the carrying capacity carrying capacity (K).(K).

Resources and Population SizeResources and Population Size As a population grows, limited resources As a population grows, limited resources

(resources in short supply) eventually (resources in short supply) eventually become depleted, and the growth of become depleted, and the growth of population slows.population slows.

Density-dependent factorsDensity-dependent factors: a variable : a variable affected by the number of organisms affected by the number of organisms present in a given area present in a given area

ex. Food and waterex. Food and water

The population model that takes into The population model that takes into account the declining resources available to account the declining resources available to populations is called the populations is called the logistic model of logistic model of population growthpopulation growth..

Logistic ModelLogistic Model: A population model in : A population model in which exponential growth is limited by a which exponential growth is limited by a density-dependent factor.density-dependent factor.

Unlike the simple model, the logistic model Unlike the simple model, the logistic model assumes that birth and death rates vary assumes that birth and death rates vary with population size.with population size.

When a population is below carrying capacity, When a population is below carrying capacity, the growth rate is rapid.the growth rate is rapid.

As the population approaches the carrying As the population approaches the carrying capacity, death rates begin to rise and capacity, death rates begin to rise and birthrates begin to decline, and the rate of birthrates begin to decline, and the rate of growth slows.growth slows.

The population stops growing when death rate The population stops growing when death rate equals the birthrate.equals the birthrate.

The logistic model of population growth The logistic model of population growth provides excellent estimates of how provides excellent estimates of how populations grow in nature.populations grow in nature.

Competition for food, shelter, mates, and Competition for food, shelter, mates, and limited resources tends to increase as a limited resources tends to increase as a population approaches its carrying capacity, population approaches its carrying capacity, and the accumulation of wastes also increases.and the accumulation of wastes also increases.

There are three stages of a There are three stages of a population modelpopulation model

Simple model (part one):Simple model (part one): Calculating the Calculating the population growth ratepopulation growth rate

r (rate of growth) = birthrate – death rater (rate of growth) = birthrate – death rate r = BR – DRr = BR – DR

Simple model (part two):Simple model (part two): Exponential growth Exponential growth curvecurve

∆∆N (change in population) = rNN (change in population) = rN ∆∆N = rNN = rN r = growth rater = growth rate N = number of individuals in the current N = number of individuals in the current

populationpopulation

More realistic model:More realistic model: Logistic Model Logistic Model K = number of members of the population at K = number of members of the population at

carrying capacitycarrying capacity ∆∆N = rN N = rN (K-N)(K-N)

KK

C.C. Growth Patterns in Real Growth Patterns in Real PopulationsPopulations

Many species of plants and insects Many species of plants and insects reproduce rapidly, but their growth reproduce rapidly, but their growth is usually limited by environmental is usually limited by environmental conditions.conditions.

Density-independent factorsDensity-independent factors:: a a variable that affects a population variable that affects a population regardless of the population density, regardless of the population density, such as climatesuch as climate Example: Weather and ClimateExample: Weather and Climate

Rapidly Growing PopulationsRapidly Growing Populations Many species, including bacteria, some plants, Many species, including bacteria, some plants,

and many insects like cockroaches and and many insects like cockroaches and mosquitoes, are found in rapidly changing mosquitoes, are found in rapidly changing environments.environments.

Such species, called Such species, called r-strategistsr-strategists, grow , grow exponentially when environmental conditions exponentially when environmental conditions allow them to reproduce.allow them to reproduce.

When the environmental conditions worsen, the When the environmental conditions worsen, the population size drops quickly.population size drops quickly.

In general, r-strategists have a short life span and In general, r-strategists have a short life span and have many offspring each time they reproduce.have many offspring each time they reproduce.

Slowly Growing PopulationsSlowly Growing Populations Organisms that grow slowly, such as Organisms that grow slowly, such as

whales, often have small population sizes.whales, often have small population sizes.

Such species, called Such species, called K-strategistsK-strategists, have , have their population density usually near the their population density usually near the carrying capacity (K) of their environment.carrying capacity (K) of their environment.

K-strategists are characterized by a long life K-strategists are characterized by a long life span, few young, a slow maturing process, span, few young, a slow maturing process, and reproduction late in life.and reproduction late in life.

Such species often provide extensive care of Such species often provide extensive care of their young and tend to live in stable their young and tend to live in stable environments.environments.

Many endangered species, such as tigers, Many endangered species, such as tigers, gorillas, and the whale, are K-strategists.gorillas, and the whale, are K-strategists.

II.II. EcosystemsEcosystems

A.A. What Is an Ecosystem?What Is an Ecosystem? Interactions of Organisms and Their Interactions of Organisms and Their

EnvironmentEnvironment We are part of the environment along with We are part of the environment along with

all of Earth’s other organisms.all of Earth’s other organisms.

All of the Earth’s organisms interact within All of the Earth’s organisms interact within an ecosystem.an ecosystem.

Removing one species from our Removing one species from our environment can have many consequences, environment can have many consequences, not all of them easily predictable.not all of them easily predictable.

EcologyEcology: the study of the interactions of living : the study of the interactions of living organisms with one another and with their organisms with one another and with their environmentenvironment

HabitatHabitat: the place where an organism usually : the place where an organism usually liveslives

CommunityCommunity: a group of species that live in the : a group of species that live in the same habitat and interact with each othersame habitat and interact with each other

EcosystemEcosystem: a community of organisms and their : a community of organisms and their abiotic environmentabiotic environment

Abiotic factorsAbiotic factors: an environmental factor that is : an environmental factor that is not associated with the activities of living not associated with the activities of living organismorganism

Biotic factorsBiotic factors: an environmental factor that is : an environmental factor that is associated with or results from the activities of associated with or results from the activities of living organismsliving organisms

EcologyEcology

Habitat Forest Community

Ecosystem

Diverse Communities in EcosystemDiverse Communities in Ecosystem

BiodiversityBiodiversity: the number and variety of : the number and variety of organisms in a given area during a specific organisms in a given area during a specific period of timeperiod of time

Ecosystem InhabitantsEcosystem Inhabitants Inhabitants of an ecosystem consist of both Inhabitants of an ecosystem consist of both

biotic factors and abiotic factors.biotic factors and abiotic factors.

Biotic factors include large animals, small Biotic factors include large animals, small animals, insects, worms, protists, bacteria, animals, insects, worms, protists, bacteria, fungi, and parasites.fungi, and parasites.

Abiotic factors include minerals, organic Abiotic factors include minerals, organic compounds, water, and wind.compounds, water, and wind.

Ecosystem BoundariesEcosystem Boundaries The physical boundaries of an ecosystem The physical boundaries of an ecosystem

are not always obvious, and they depend are not always obvious, and they depend on how the ecosystem is being studied.on how the ecosystem is being studied.

Change of Ecosystem over TimeChange of Ecosystem over Time When a volcano forms a new island, a glacier When a volcano forms a new island, a glacier

recedes and exposes bare rock, or a fire burns recedes and exposes bare rock, or a fire burns all of the vegetation in an area, a new habitat all of the vegetation in an area, a new habitat is created.is created.

This change sets off a process of colonization This change sets off a process of colonization and ecosystem development.and ecosystem development.

The first organisms to live in a new habitat The first organisms to live in a new habitat where soil is present tend to be small, fast-where soil is present tend to be small, fast-growing plants, called pioneer species.growing plants, called pioneer species.

Pioneer speciesPioneer species: a species that colonizes an : a species that colonizes an uninhabited area and that starts an ecological uninhabited area and that starts an ecological cycle in which many other species become cycle in which many other species become establishedestablished

SuccessionSuccession SuccessionSuccession:: the replacement of one the replacement of one

type of community by another at a type of community by another at a single location over a period of timesingle location over a period of time

There are two main types of successionThere are two main types of succession Primary SuccessionPrimary Succession

Succession that begins in an area that previously Succession that begins in an area that previously did not support lifedid not support life

Secondary SuccessionSecondary Succession The process by which one community replaces The process by which one community replaces

another community that has been partially or another community that has been partially or totally destroyedtotally destroyed

Initial conditions and chance play Initial conditions and chance play roles in the process of succession.roles in the process of succession.

SuccessionSuccession

Primary SuccessionSecondary Succession

Glacier Bay: An Example of SuccessionGlacier Bay: An Example of Succession Receding glacier allowed primary Receding glacier allowed primary

succession to take placesuccession to take place

Receding glacier left an area with rocks Receding glacier left an area with rocks and gravel that lack the usable nitrogen and gravel that lack the usable nitrogen essential to plant and animal lifeessential to plant and animal life

Pioneer species like lichens, mosses, Pioneer species like lichens, mosses, fireweed, willows, cottonwood, and Dryas.fireweed, willows, cottonwood, and Dryas.

Dryas crowd out the other plants and take Dryas crowd out the other plants and take over.over.

After about 10 years, alder seeds take root.After about 10 years, alder seeds take root.

Alder roots have nitrogen-fixing Alder roots have nitrogen-fixing nodules, so they are able to grow more nodules, so they are able to grow more rapidly than Dryas.rapidly than Dryas.

About 30 years, dense thickets of alder, About 30 years, dense thickets of alder, willow, and cottonwood shade and kill willow, and cottonwood shade and kill the Dryas.the Dryas.

In about 80 years, Sitka spruce invades In about 80 years, Sitka spruce invades the thickets, and the alders die out the thickets, and the alders die out since the spruce blocks the sunlight.since the spruce blocks the sunlight.

Finally, Hemlocks grow and establish a Finally, Hemlocks grow and establish a stable ecosystem with the spruce.stable ecosystem with the spruce.

Glacier BayGlacier Bay

B.B. Energy Flow in Energy Flow in EcosystemsEcosystems

Movement of Energy Through Movement of Energy Through EcosystemsEcosystems Everything that organisms do in Everything that organisms do in

ecosystems requires energy.ecosystems requires energy. The flow of energy is the most The flow of energy is the most

important factor that controls what important factor that controls what kinds of organisms live in an ecosystem kinds of organisms live in an ecosystem and how many organisms the ecosystem and how many organisms the ecosystem can support.can support.

Primary Energy SourcePrimary Energy Source Most life on Earth depends on Most life on Earth depends on

photosynthetic organisms, which capture photosynthetic organisms, which capture some of the sun’s light energy and store it some of the sun’s light energy and store it as chemical energy in organic molecules as chemical energy in organic molecules (food).(food).

Primary productivity:Primary productivity: the total amount the total amount of organic material that the autotrophic of organic material that the autotrophic organisms of an ecosystem produceorganisms of an ecosystem produce

Primary productivity determines the Primary productivity determines the amount of energy available in an amount of energy available in an ecosystem.ecosystem.

Organisms that first capture energy, Organisms that first capture energy, producers, include plants, some kinds of producers, include plants, some kinds of bacteria, and algaebacteria, and algae

ProducerProducer: an organism that can make : an organism that can make organic molecules from inorganic organic molecules from inorganic molecules; a photosynthetic or molecules; a photosynthetic or chemosynthetic autotroph that serves chemosynthetic autotroph that serves as the basic food source in an as the basic food source in an ecosystemecosystem

All other organisms in an ecosystem are All other organisms in an ecosystem are consumers.consumers.

Consumers:Consumers: an organism that eats an organism that eats other organisms or organic matter other organisms or organic matter instead of producing its own nutrients instead of producing its own nutrients or obtaining nutrients from inorganic or obtaining nutrients from inorganic sources.sources.

Trophic LevelsTrophic Levels In order to study how energy moves In order to study how energy moves

through an ecosystem, organisms are through an ecosystem, organisms are placed in into trophic levels.placed in into trophic levels.

Trophic levelTrophic level: One of the steps in a : One of the steps in a food chain or food pyramidfood chain or food pyramid

Energy moves from one trophic level to Energy moves from one trophic level to anotheranother

The sun is the ultimate source of The sun is the ultimate source of energy.energy.

Food chainFood chain: the pathway of : the pathway of energy transfer through various energy transfer through various stages as a result of the feeding stages as a result of the feeding patterns of a series of organismspatterns of a series of organisms

The lowest trophic level (first level) for The lowest trophic level (first level) for any ecosystem is occupied by producers any ecosystem is occupied by producers (algae, bacteria, plants).(algae, bacteria, plants).

Producers use the energy of the sun to Producers use the energy of the sun to build energy-rich carbohydrates, as well build energy-rich carbohydrates, as well as absorb nitrogen and other key as absorb nitrogen and other key substances.substances.

First trophic level-

producers

Producer’s JobProducer’s Job

At the second trophic level are At the second trophic level are herbivores.herbivores.

HerbivoresHerbivores: an organism that eats : an organism that eats only plantsonly plants

Herbivores eat the primary producers Herbivores eat the primary producers so they are also known as the primary so they are also known as the primary consumers.consumers.

A herbivore must be able to break down A herbivore must be able to break down a plant’s molecules into usable a plant’s molecules into usable compounds.compounds.

Second trophic Level-

herbivores

Most herbivores rely on Most herbivores rely on microorganisms, such as bacteria and microorganisms, such as bacteria and protists, in their gut to help them digest protists, in their gut to help them digest cellulose. cellulose. Example: cow and horseExample: cow and horse

Humans cannot digest cellulose Humans cannot digest cellulose because they lack these special because they lack these special microorganisms.microorganisms.

At the third trophic level are secondary At the third trophic level are secondary consumers (animals that eat other consumers (animals that eat other animals).animals).

CarnivoresCarnivores: an animal that eats other : an animal that eats other animalsanimals

Some animals are both herbivores and Some animals are both herbivores and carnivores; they are called carnivores; they are called omnivoresomnivores

They use the simple sugars and They use the simple sugars and starches stored in plants as food, but starches stored in plants as food, but they cannot digest cellulose.they cannot digest cellulose.

Third trophic level -

Carnivore

There is a special class of consumers There is a special class of consumers called detritivores, which include worms, called detritivores, which include worms, fungal, and bacterial decomposers.fungal, and bacterial decomposers.

Detritivores:Detritivores: a consumer that feeds on a consumer that feeds on dead plants and animals at all trophic dead plants and animals at all trophic levelslevels

Bacteria and fungi are known as Bacteria and fungi are known as decomposerdecomposer because they cause decay. because they cause decay.

Decomposer:Decomposer: an organism that feeds by an organism that feeds by breaking down organic matter from dead breaking down organic matter from dead organismsorganisms

Decomposition of bodies and wastes Decomposition of bodies and wastes releases nutrients back into the releases nutrients back into the environment to be recycled by other environment to be recycled by other organisms.organisms.

The fourth trophic level is composed of The fourth trophic level is composed of tertiary consumers (carnivores that tertiary consumers (carnivores that consume other carnivores)consume other carnivores)

Energy does not follow simple straight Energy does not follow simple straight paths because individual animals often paths because individual animals often feed at several trophic levels.feed at several trophic levels.

Food webFood web: a diagram that shows the : a diagram that shows the feeding relationships between feeding relationships between organisms in an ecosystem organisms in an ecosystem

Loss of Energy in a Food ChainLoss of Energy in a Food Chain Organisms acquire energy from their Organisms acquire energy from their

environment.environment. The energy that organisms obtain help The energy that organisms obtain help

aid their cellular processes.aid their cellular processes. Much of the energy obtained is Much of the energy obtained is

dispersed into the environment as heat.dispersed into the environment as heat.

Energy TransferEnergy Transfer During every transfer of energy within During every transfer of energy within

an ecosystem, energy is lost as heat.an ecosystem, energy is lost as heat. The amount of useful energy available The amount of useful energy available

to do work decreases as energy passes to do work decreases as energy passes through an ecosystem.through an ecosystem.

The loss of useful energy limits the The loss of useful energy limits the number of trophic levels an ecosystem number of trophic levels an ecosystem can support.can support.

At each trophic level, the energy stored At each trophic level, the energy stored by the organisms in a level is about one-by the organisms in a level is about one-tenth of that stored by the organisms in tenth of that stored by the organisms in the level below.the level below.

The Pyramid of EnergyThe Pyramid of Energy The flow of energy through ecosystems The flow of energy through ecosystems

is illustrated with an is illustrated with an energy pyramidenergy pyramid.. Energy pyramid:Energy pyramid: a triangular diagram a triangular diagram

that shows an ecosystem’s loss of that shows an ecosystem’s loss of energy, which results as energy passes energy, which results as energy passes through the ecosystem’s food chainthrough the ecosystem’s food chain

Each trophic level is represented by a Each trophic level is represented by a block.block.

The width of each block is determined The width of each block is determined by the amount of energy stored in the by the amount of energy stored in the organisms at that trophic level.organisms at that trophic level.

Limitations of Trophic LevelsLimitations of Trophic Levels The number of trophic levels that can The number of trophic levels that can

be maintained in a community is limited be maintained in a community is limited by the dispersal of potential energy.by the dispersal of potential energy.

The number of individuals in a trophic The number of individuals in a trophic level may not be an accurate indicator level may not be an accurate indicator of the amount of energy in that level.of the amount of energy in that level.

In order to determine the amount of In order to determine the amount of energy present in trophic levels, energy present in trophic levels, ecologist measure ecologist measure biomassbiomass..

Biomass:Biomass: organic matter that can be a organic matter that can be a source of energy; the total mass of the source of energy; the total mass of the organisms in a given areaorganisms in a given area

BiomassBiomass

C.C. Cycling of Materials in Cycling of Materials in EcosystemsEcosystems

Biogeochemical CyclesBiogeochemical Cycles All materials that cycle through living All materials that cycle through living

organism are important in maintaining organism are important in maintaining the health of ecosystems.the health of ecosystems.

Four substances that are important in Four substances that are important in this process are: Water, carbon, this process are: Water, carbon, nitrogen, and phosphorus.nitrogen, and phosphorus.

All organisms require carbon, All organisms require carbon, hydrogen, oxygen, nitrogen, hydrogen, oxygen, nitrogen, phosphorus, and sulfur in relatively phosphorus, and sulfur in relatively large quantities.large quantities.

The paths of water, carbon, nitrogen, The paths of water, carbon, nitrogen, and phosphorus pass from the nonliving and phosphorus pass from the nonliving environment to living organisms, and environment to living organisms, and then back to the nonliving environment.then back to the nonliving environment.

These paths form closed circles, or These paths form closed circles, or cycles, called cycles, called biogeochemical cycles.biogeochemical cycles.

Biogeochemical cycles:Biogeochemical cycles: the the circulation of substances through living circulation of substances through living organisms from or to the environmentorganisms from or to the environment

The Water CycleThe Water Cycle Of all the nonliving components of an Of all the nonliving components of an

ecosystem, water has the greatest influence ecosystem, water has the greatest influence on the ecosystems inhabitants.on the ecosystems inhabitants.

In the nonliving portion of the water cycle, In the nonliving portion of the water cycle, water vapor in the atmosphere condenses water vapor in the atmosphere condenses and falls on the Earth’s surface as rain or and falls on the Earth’s surface as rain or snow.snow.

Some of this water seeps into the soil and Some of this water seeps into the soil and becomes part of the becomes part of the ground waterground water (water (water that is beneath the Earth’s surface)that is beneath the Earth’s surface)

The remaining water on the Earth’s surface The remaining water on the Earth’s surface is heated by the sun and reenters the is heated by the sun and reenters the atmosphere by evaporation.atmosphere by evaporation.

In the living portion of the water cycle, much In the living portion of the water cycle, much water is taken up by the roots of plants.water is taken up by the roots of plants.

After passing through a plant, the water moves After passing through a plant, the water moves into the atmosphere by evaporating from the into the atmosphere by evaporating from the leaves, a process called leaves, a process called transpiration.transpiration.

Transpiration is also a sun-driven process.Transpiration is also a sun-driven process. In aquatic ecosystems (lakes, rivers, and In aquatic ecosystems (lakes, rivers, and

oceans), the nonliving portion of the water oceans), the nonliving portion of the water cycle is the most important.cycle is the most important.

In terrestrial ecosystems, the nonliving and In terrestrial ecosystems, the nonliving and living parts of the water cycle both play living parts of the water cycle both play important roles.important roles.

Water CycleWater Cycle

Transpiration

The Carbon CycleThe Carbon Cycle Carbon also cycles between the nonliving Carbon also cycles between the nonliving

environment and living organisms.environment and living organisms. Carbon dioxide in the air or dissolved in water is Carbon dioxide in the air or dissolved in water is

used by photosynthesizing plants, algae, and used by photosynthesizing plants, algae, and bacteria as a raw material to build organic bacteria as a raw material to build organic molecules.molecules.

Carbon atoms may return to the pool of carbon Carbon atoms may return to the pool of carbon dioxide in the air and water in three ways:dioxide in the air and water in three ways:

RespirationRespiration

Nearly all living organisms engage in Nearly all living organisms engage in cellular respiration.cellular respiration.

They use oxygen to oxidize organic They use oxygen to oxidize organic molecules during cellular respiration, and molecules during cellular respiration, and carbon dioxide is a byproduct of this carbon dioxide is a byproduct of this reaction.reaction.

CombustionCombustion Carbon returns to the atmosphere Carbon returns to the atmosphere

through combustion, or burning.through combustion, or burning. The burning wood or fossil fuels The burning wood or fossil fuels

(coal, oil, and natural gas) releases (coal, oil, and natural gas) releases carbon into the atmosphere.carbon into the atmosphere.

ErosionErosion Marine organisms use carbon dioxide Marine organisms use carbon dioxide

dissolved in sea water to make calcium dissolved in sea water to make calcium carbonate shells.carbonate shells.

These shells form sediments, which form These shells form sediments, which form limestone, and as it erodes, the carbon limestone, and as it erodes, the carbon becomes available to other organisms.becomes available to other organisms.

Carbon CycleCarbon Cycle

Dissolved CO2 in water

The Phosphorus and Nitrogen The Phosphorus and Nitrogen CyclesCycles Organisms need nitrogen and Organisms need nitrogen and

phosphorus to build proteins and phosphorus to build proteins and nucleic acids.nucleic acids.

Phosphorus is an essential part of both Phosphorus is an essential part of both ATP and DNA.ATP and DNA.

Phosphorus is usually present in soil Phosphorus is usually present in soil and rock as calcium phosphate, which and rock as calcium phosphate, which dissolves in water to form phosphate dissolves in water to form phosphate ions, PO43-.ions, PO43-.

This phosphate is absorbed by the roots This phosphate is absorbed by the roots of plants and used to build organic of plants and used to build organic molecules molecules

Phosphorus CyclePhosphorus Cycle

The atmosphere is about 78 percent nitrogen The atmosphere is about 78 percent nitrogen gas, N2, which is not usable by organisms.gas, N2, which is not usable by organisms.

The two nitrogen atoms in a molecule of The two nitrogen atoms in a molecule of nitrogen gas are connected by a strong triple nitrogen gas are connected by a strong triple covalent bond that is very difficult to break.covalent bond that is very difficult to break.

Few bacteria have enzymes that can break it, Few bacteria have enzymes that can break it, and they bind nitrogen atoms to hydrogen to and they bind nitrogen atoms to hydrogen to form ammonia, NH3.form ammonia, NH3.

The process of combining nitrogen with The process of combining nitrogen with hydrogen to form ammonia is called hydrogen to form ammonia is called nitrogen fixationnitrogen fixation..

Nitrogen-fixing bacteria live in the soil and Nitrogen-fixing bacteria live in the soil and are also found within swellings, or nodules, are also found within swellings, or nodules, on roots of beans, alder trees, and few other on roots of beans, alder trees, and few other kinds of plants.kinds of plants.

Nitrogen FixationNitrogen Fixation

There are four important stages in There are four important stages in the nitrogen cycle:the nitrogen cycle: AssimilationAssimilation

The absorption and incorporation of The absorption and incorporation of nitrogen into organic compounds by plants.nitrogen into organic compounds by plants.

AmmonificationAmmonification The production of ammonia by bacteria The production of ammonia by bacteria

during the decay of organic matter.during the decay of organic matter. NitrificationNitrification

Production of nitrate from ammonia.Production of nitrate from ammonia. DenitrificationDenitrification

The conversion of nitrate to nitrogen gas.The conversion of nitrate to nitrogen gas.

Nitrogen CycleNitrogen Cycle

The growth of plants in ecosystems is The growth of plants in ecosystems is often limited by the availability of often limited by the availability of nitrate and ammonia in the soil.nitrate and ammonia in the soil.

Today, most of the ammonia and nitrate Today, most of the ammonia and nitrate that farmers add to soil is produced that farmers add to soil is produced chemically in factories, rather than by chemically in factories, rather than by bacterial nitrogen fixation.bacterial nitrogen fixation.Reminder: TEST MONDAY

III.III. Biological Biological CommunitiesCommunities

A.A. Common Use of Scarce Common Use of Scarce Resources and CompetitionResources and Competition

When two species use the same When two species use the same resource, they participate in a biological resource, they participate in a biological interaction called interaction called competitioncompetition..

Competition:Competition: the relationship between the relationship between species that attempt to use the same species that attempt to use the same limited resourcelimited resource

Resources for which species compete Resources for which species compete include food, nesting sites, living space, include food, nesting sites, living space, light, mineral nutrients, and water.light, mineral nutrients, and water.

Video: Giant Octopus Battles SharkVideo: Giant Octopus Battles Shark

CompetitionCompetition

The functional role of a particular species The functional role of a particular species in an ecosystem is called its in an ecosystem is called its nicheniche..

NicheNiche: the position (way of life) of a : the position (way of life) of a species in an ecosystem in terms of the species in an ecosystem in terms of the physical characteristics (such as size, physical characteristics (such as size, location, temperature, and pH) of the area location, temperature, and pH) of the area where the species lives and the function of where the species lives and the function of the species in the biological community. the species in the biological community.

Video: Humpback Whales' Feeding FrenzyVideo: Humpback Whales' Feeding Frenzy A niche may be described in terms of A niche may be described in terms of

space utilization, food consumption, space utilization, food consumption, temperature range, requirements for temperature range, requirements for moisture or mating, and other factors.moisture or mating, and other factors.

A niche is not a habitat (a location), it’s a A niche is not a habitat (a location), it’s a pattern of living.pattern of living.

Example: Example: Jaguar’s NicheJaguar’s Niche DietDiet: feed on mammals, fish, and : feed on mammals, fish, and

turtlesturtles ReproductionReproduction: Give birth from June : Give birth from June

to August, during rainy seasonto August, during rainy season Time of ActivityTime of Activity: Hunt by day and by : Hunt by day and by

nightnight

A niche is often described in terms of how A niche is often described in terms of how the organism affects energy flow within the organism affects energy flow within the ecosystem in which it lives.the ecosystem in which it lives.

The niches of some organisms overlap and The niches of some organisms overlap and if the resources that these resources share if the resources that these resources share are in short supply, it is likely that there are in short supply, it is likely that there will be competition between organisms.will be competition between organisms.

Size of a Specie’s NicheSize of a Specie’s Niche The entire range of resource opportunities The entire range of resource opportunities

an organism is potentially able to occupy an organism is potentially able to occupy within an ecosystem is its within an ecosystem is its fundamental fundamental nicheniche..

Fundamental nicheFundamental niche: the largest : the largest ecological niche where an organism or ecological niche where an organism or species can live without competitionspecies can live without competition

Example: Cape May warbler (small Example: Cape May warbler (small insect-eating song bird)insect-eating song bird) Finds food in spruce treeFinds food in spruce tree Nests midsummerNests midsummer Eats small insectsEats small insects Searches for food high on the spruce Searches for food high on the spruce

treestrees

Dividing Resources Among SpeciesDividing Resources Among Species The part of its fundamental niche that a The part of its fundamental niche that a

species occupies is called its species occupies is called its realized realized nicheniche..

Realized nicheRealized niche: the range of : the range of resources that a species uses, the resources that a species uses, the conditions that the species can tolerate, conditions that the species can tolerate, and the functional roles that the species and the functional roles that the species plays as a result of competition in the plays as a result of competition in the specie’s fundamental nichespecie’s fundamental niche

The realized niche is only a small The realized niche is only a small portion of its fundamental niche which portion of its fundamental niche which reduces competition among species.reduces competition among species.

Example: five warbler species feeds Example: five warbler species feeds on insects in a different portion of on insects in a different portion of the same treethe same tree

B.B. Competition and Competition and Limitations of Resource Limitations of Resource UseUse

Competition can limit how species use Competition can limit how species use resourcesresources Example:Example: 1960’s Experiment done by Joseph 1960’s Experiment done by Joseph

ConnellConnell Joseph worked with barnacles (marine animals Joseph worked with barnacles (marine animals

that attach themselves to rocks)that attach themselves to rocks) Connell studied two species of barnacles that Connell studied two species of barnacles that

grow on the same rocks along the coast of grow on the same rocks along the coast of Scotland.Scotland.

Chthamalus stellatusChthamalus stellatus, lives in shallow water, , lives in shallow water, where it is often exposed to air by receding where it is often exposed to air by receding tidestides

Semibalanus balanoidesSemibalanus balanoides, lives lower down on , lives lower down on the rocks, where it is rarely exposed to the the rocks, where it is rarely exposed to the atmosphere.atmosphere.

Connell removed Connell removed SemibalanusSemibalanus from the from the deeper zone, and the deeper zone, and the Chthamalus Chthamalus was was easily able to occupy the vacant surfaces.easily able to occupy the vacant surfaces.

When the When the SemibalanusSemibalanus was reintroduced, was reintroduced, it outcompeted it outcompeted Chthamalus Chthamalus by crowding by crowding if off the rocks.if off the rocks.

In contrast, In contrast, SemibalanusSemibalanus could not could not survive when placed in the shallow water.survive when placed in the shallow water.

The realized niche of The realized niche of ChthalamusChthalamus is is smaller than its fundamental niche smaller than its fundamental niche because of competition from the faster-because of competition from the faster-growing growing SemibalabusSemibalabus..

Connell’s ExperimentConnell’s Experiment

C.C. Competition Without Competition Without Division of ResourcesDivision of Resources

G. F. Gause looked at competition G. F. Gause looked at competition between similar species.between similar species.

Gauses experiment showed that the Gauses experiment showed that the outcome of competition depends on the outcome of competition depends on the degree of similarity between the degree of similarity between the fundamental niches of the competing fundamental niches of the competing species.species.

Gause hypothesized that if two species Gause hypothesized that if two species are competing, the species that uses the are competing, the species that uses the resource more efficiently will eventually resource more efficiently will eventually eliminate the other.eliminate the other.

This elimination of competing species is This elimination of competing species is referred to as referred to as competitive exclusioncompetitive exclusion..

Competitive exclusion:Competitive exclusion: the exclusion the exclusion of one species by another due to of one species by another due to competitioncompetition Experiment:Experiment: Gause Experiment I Gause Experiment I Grew two species of Grew two species of ParameciumParamecium in in

the same culture tubes, where they the same culture tubes, where they had to compete for the same food.had to compete for the same food.

The smaller of the two species, which The smaller of the two species, which was more resistant to bacterial waste was more resistant to bacterial waste products, drove the larger one to products, drove the larger one to extinctionextinction

Gause’s Experiment IGause’s Experiment I

When can Competitors Coexist?When can Competitors Coexist? When species avoid competition, they When species avoid competition, they

may coexist.may coexist.Example: Gause Experiment IIExample: Gause Experiment IIPlaced Placed P.caudatumP.caudatum and and P.bursariaP.bursaria in the same culture tubes, where in the same culture tubes, where they had to compete for the same they had to compete for the same food.food.

Instead of one species winning the Instead of one species winning the competition, both species survivedcompetition, both species survived

P. caudatumP. caudatum was found in the upper was found in the upper part of the culture tube were they part of the culture tube were they feed on bacteriafeed on bacteria

P.bursariaP.bursaria on the other hand on the other hand were found in the bottom of the were found in the bottom of the culture tube were they feed on culture tube were they feed on yeastyeast

The fundamental niche of each The fundamental niche of each species was the whole culture species was the whole culture tube, but the realized niche of tube, but the realized niche of each species was only a portion each species was only a portion of the tube.of the tube.

Therefore, when two species Therefore, when two species used different resources, both used different resources, both were able to survive.were able to survive.

Gause’s Experiment IIGause’s Experiment II

Predation and CompetitionPredation and Competition Many studies have shown that Many studies have shown that

predation reduces the effects of predation reduces the effects of competition.competition.

Because predation can reduce Because predation can reduce competition, it can also promote competition, it can also promote biodiversity (the variety of living biodiversity (the variety of living organisms present in a community)organisms present in a community)

Biodiversity is a measure of both the Biodiversity is a measure of both the number of different species in a number of different species in a community (species richness) and community (species richness) and the relative numbers of each of the the relative numbers of each of the species (species diversity)species (species diversity)

Example: Paine’s ExperimentExample: Paine’s Experiment Paine examined how sea stars affect Paine examined how sea stars affect

the numbers and types of species the numbers and types of species within marine intertidal communities.within marine intertidal communities.

Sea stars are fierce predators of Sea stars are fierce predators of clams and mussels.clams and mussels.

When the sea stars were eliminate, When the sea stars were eliminate, Paine noticed that the sea stars prey Paine noticed that the sea stars prey species fell from 15 to 8.species fell from 15 to 8.

Paine noticed that the mussels were Paine noticed that the mussels were taking overtaking over

By preying on mussels, sea stars keep By preying on mussels, sea stars keep the mussel populations too low to the mussel populations too low to drive out other species.drive out other species.

Biodiversity and ProductivityBiodiversity and Productivity More biodiversity leads to more More biodiversity leads to more

productivity.productivity. Example: Tilman’s experimentExample: Tilman’s experiment Tended 207 experimental plots in Tended 207 experimental plots in

MinnesotaMinnesota Each plot contained a mix of up to 24 Each plot contained a mix of up to 24

native prairie plant speciesnative prairie plant species They measure how much growth was They measure how much growth was

occurringoccurring The greater number of species a plot The greater number of species a plot

had, the greater the amount of plant had, the greater the amount of plant material produced in that plot.material produced in that plot.

Plots with greater number of species also Plots with greater number of species also recovered more fully after a disaster.recovered more fully after a disaster.

IV.IV. The EnvironmentThe Environment

A.A. Global ChangeGlobal Change The Atmosphere and EcosystemsThe Atmosphere and Ecosystems

Human –induced environmental changes area Human –induced environmental changes area affecting ecosystems worldwide and may lead affecting ecosystems worldwide and may lead to global change.to global change.

Acid RainAcid Rain Coal-burning power plants send smoke high Coal-burning power plants send smoke high

into atmosphere through tall smokestacks.into atmosphere through tall smokestacks. This smoke contains high concentrations of This smoke contains high concentrations of

sulfur because the coal that the plant burns is sulfur because the coal that the plant burns is rich in sulfur.rich in sulfur.

Scientists have discovered that the sulfur Scientists have discovered that the sulfur introduced into the atmosphere by introduced into the atmosphere by smokestacks can combine with water vapor to smokestacks can combine with water vapor to produce sulfuric acid.produce sulfuric acid.

Rain and snow carry the sulfuric acid back Rain and snow carry the sulfuric acid back to the Earth’s surface.to the Earth’s surface.

This acidified precipitation is called This acidified precipitation is called acid acid rainrain..

Acid RainAcid Rain: precipitation that has a pH : precipitation that has a pH below normal and has an unusually high below normal and has an unusually high concentration of sulfuric or nitric acids, concentration of sulfuric or nitric acids, often as a result of chemical pollution of the often as a result of chemical pollution of the air from sources such as automobiles air from sources such as automobiles exhaust and the burning of fossil fuelsexhaust and the burning of fossil fuels

In North America, acid rain is most In North America, acid rain is most severe in the northeastern United severe in the northeastern United States and in southeastern Canada, States and in southeastern Canada, areas that are downwind from coal-areas that are downwind from coal-burning plants in the Midwest.burning plants in the Midwest.

In the northeastern United States, In the northeastern United States, rain and snow have an average pH of rain and snow have an average pH of about 4.0 – 4.5 (water pH is 7.0)about 4.0 – 4.5 (water pH is 7.0)

Rainwater and some soils are Rainwater and some soils are naturally slightly acidic.naturally slightly acidic.

The acidity added by human activity The acidity added by human activity is having a dramatic effect.is having a dramatic effect.

In the United States and Canada, thousands In the United States and Canada, thousands of lakes are “dying” as their pH levels fall of lakes are “dying” as their pH levels fall below 5.0below 5.0

Forests in the eastern United States and Forests in the eastern United States and southern Canada are being damaged southern Canada are being damaged because the acid pH may be harming because the acid pH may be harming symbiotic fungi in their roots.symbiotic fungi in their roots.

The Ozone LayerThe Ozone Layer The ozone layer is a protective shield The ozone layer is a protective shield

against the sun’s damaging rays.against the sun’s damaging rays. The ozone layer is being reduced, and The ozone layer is being reduced, and

human activity may play a large role in its human activity may play a large role in its reduction.reduction.

The Ozone HoleThe Ozone Hole In 1985, a researcher in Antarctica noticed In 1985, a researcher in Antarctica noticed

that ozone levels in the atmosphere that ozone levels in the atmosphere seemed to be as much as 35 percent lower seemed to be as much as 35 percent lower than the average values during 1960s.than the average values during 1960s.

Satellite images taken over the South Pole Satellite images taken over the South Pole revealed that the ozone concentration was revealed that the ozone concentration was unexpectedly lower over the Antarctica unexpectedly lower over the Antarctica than elsewhere in the Earth’s atmosphere than elsewhere in the Earth’s atmosphere (ozone hole).(ozone hole).

Ozone Layer and Ozone Ozone Layer and Ozone HoleHole

Scientist found that the disintegration Scientist found that the disintegration of the Earth’s ozone shield was evident of the Earth’s ozone shield was evident as far back as 1978.as far back as 1978.

Every year since then, more ozone has Every year since then, more ozone has disappeared, and the ozone hole has disappeared, and the ozone hole has grown larger, plus a smaller hole has grown larger, plus a smaller hole has appeared over the Artic.appeared over the Artic.

The decrease in ozone allows more The decrease in ozone allows more ultraviolet radiation to reach Earth’s ultraviolet radiation to reach Earth’s surface that scientist expect an surface that scientist expect an increased incidence of diseases caused increased incidence of diseases caused by exposure to ultraviolet radiation.by exposure to ultraviolet radiation.

These diseases include skin cancer, These diseases include skin cancer, cataracts, and cancer of the retina.cataracts, and cancer of the retina.

Skin cancer, Cataracts, Cancer of Skin cancer, Cataracts, Cancer of the Retinathe Retina

What is Destroying Ozone?What is Destroying Ozone? The major cause of ozone destruction is The major cause of ozone destruction is

a class of chemicals called a class of chemicals called chlorofluorocarbons (CFCs)chlorofluorocarbons (CFCs)..

Chlorofluorocarbons: hydrocarbon in Chlorofluorocarbons: hydrocarbon in which some or all of the hydrogen which some or all of the hydrogen atoms are replaced by chlorine and atoms are replaced by chlorine and fluorine; used in coolants for fluorine; used in coolants for refrigerators and air conditioners and in refrigerators and air conditioners and in cleaning solvents; their use is restricted cleaning solvents; their use is restricted because they destroy the ozone layerbecause they destroy the ozone layer

CFCs were invented in the 1920s CFCs were invented in the 1920s because were considered extremely because were considered extremely stable, supposedly harmless, and a stable, supposedly harmless, and a nearly ideal heat exchanger.nearly ideal heat exchanger.

By 1985, the scientific community had By 1985, the scientific community had learned that CFCs are the primary learned that CFCs are the primary cause of the ozone hole.cause of the ozone hole.

High in the atmosphere, ultraviolet High in the atmosphere, ultraviolet radiation from the sun is able to break radiation from the sun is able to break the usually stable bonds in CFCs.the usually stable bonds in CFCs.

The resulting free chlorine atoms then The resulting free chlorine atoms then enter into a series of reactions that enter into a series of reactions that destroy ozone.destroy ozone.

As a result of this discovery, CFCs have As a result of this discovery, CFCs have been banned as aerosol propellants in been banned as aerosol propellants in spray cans in the United States.spray cans in the United States.

Global TemperaturesGlobal Temperatures The average global temperature has The average global temperature has

been steadily increasing for more than been steadily increasing for more than a century, particularly since the 1950s.a century, particularly since the 1950s.

In the Earth’s long history there have In the Earth’s long history there have been many such periods of been many such periods of global global warmingwarming, often followed by centuries of , often followed by centuries of cold.cold.

Scientist hypothesize that sunspot Scientist hypothesize that sunspot cycles may contribute to these cyclical cycles may contribute to these cyclical changes in global temperature, but changes in global temperature, but many scientists suspect that human many scientists suspect that human activity may be significantly activity may be significantly contributing to global warming.contributing to global warming.

Global WarmingGlobal Warming

The Greenhouse EffectThe Greenhouse Effect Greenhouse gases, such as water vapor, Greenhouse gases, such as water vapor,

carbon dioxide, methane, and nitrous carbon dioxide, methane, and nitrous oxide, prevent the Earth from being oxide, prevent the Earth from being cold as the moon.cold as the moon.

The chemical bonds in carbon dioxide The chemical bonds in carbon dioxide (CO(CO22) molecules absorb solar energy as ) molecules absorb solar energy as heat radiates from Earth.heat radiates from Earth.

This process, called the This process, called the greenhouse greenhouse effecteffect, traps heat within the , traps heat within the atmosphere.atmosphere.

Greenhouse effectGreenhouse effect: the warming of the : the warming of the surface of Earth and the lower surface of Earth and the lower atmosphere as a result of carbon atmosphere as a result of carbon dioxide and water vapor, which absorb dioxide and water vapor, which absorb and reradiate infrared radiation.and reradiate infrared radiation.

There has been a large increase in There has been a large increase in carbon dioxide in the Earth’s carbon dioxide in the Earth’s atmosphere which can be related to the atmosphere which can be related to the burning of fossil fuels.burning of fossil fuels.

Greenhouse EffectGreenhouse Effect

Is Global Warming Occurring?Is Global Warming Occurring? The correlation of increasing The correlation of increasing

temperature with increasing carbon temperature with increasing carbon dioxide levels is very close.dioxide levels is very close.

Therefore many scientists are Therefore many scientists are convinced temperature and carbon convinced temperature and carbon dioxide levels are related.dioxide levels are related.

Both global temperature and levels of Both global temperature and levels of greenhouse gases may be changing greenhouse gases may be changing because of other variables that have not because of other variables that have not been recognized yet.been recognized yet.

B.B. Effects on EcosystemEffects on Ecosystem

Effects of Chemical PollutionEffects of Chemical Pollution One important urban environmental One important urban environmental

problem is chemical pollution.problem is chemical pollution. People assumed that the environment People assumed that the environment

can absorb any amount of pollution.can absorb any amount of pollution. Lake Erie and other large lakes Lake Erie and other large lakes

became polluted because of the became polluted because of the assumption that they could absorb assumption that they could absorb unlimited amounts of industrial unlimited amounts of industrial chemicals.chemicals.

Small oil spills and leaks receive little Small oil spills and leaks receive little or no publicity account for more than or no publicity account for more than 90 percent of all pollution.90 percent of all pollution.

Many of the most disastrous incidents Many of the most disastrous incidents of pollution involve industrial of pollution involve industrial chemicals that are toxic or chemicals that are toxic or carcinogenic (cancer-causing)carcinogenic (cancer-causing)

Until recently, there has been Until recently, there has been relatively little regulation of the relatively little regulation of the manufacture, transportation, storage, manufacture, transportation, storage, and destruction of such chemicals.and destruction of such chemicals.

Agricultural ChemicalsAgricultural Chemicals In many countries, modern agriculture In many countries, modern agriculture

introduces large amounts of chemicals into introduces large amounts of chemicals into the global ecosystem.the global ecosystem.

These chemicals include pesticides, These chemicals include pesticides, herbicides, and fertilizers.herbicides, and fertilizers.

Industrialized countries, like United States, Industrialized countries, like United States, now attempt to carefully monitor side now attempt to carefully monitor side effects of these chemicals.effects of these chemicals.

Unfortunately, large quantities of many Unfortunately, large quantities of many toxic chemicals that are no longer toxic chemicals that are no longer manufactured still circulate in the manufactured still circulate in the ecosystem.ecosystem.

Pesticides are molecules of chlorinated Pesticides are molecules of chlorinated hydrocarbons that break down slowly in the hydrocarbons that break down slowly in the environment and accumulate in the fatty environment and accumulate in the fatty tissue of animals.tissue of animals.

These pesticides include DDT, These pesticides include DDT, chlordane, lindane, and dieldrin.chlordane, lindane, and dieldrin.

As these molecules pass up through the As these molecules pass up through the trophic levels of food chain, they trophic levels of food chain, they become increasingly concentrated, and become increasingly concentrated, and this process is called this process is called biological biological magnificationmagnification..

Biological magnificationBiological magnification: the : the accumulation of increasingly large accumulation of increasingly large amounts of toxic substances within each amounts of toxic substances within each successive link of the food chain.successive link of the food chain.

Biological MagnificationBiological Magnification

Example:Example: Pesticide DDT Pesticide DDT Presence of DDT in birds causes thin, Presence of DDT in birds causes thin,

fragile eggshells, which can break fragile eggshells, which can break during incubation.during incubation.

Many predatory birds in the United Many predatory birds in the United States and elsewhere failed to States and elsewhere failed to reproduce, and their numbers reproduce, and their numbers dwindled.dwindled.

In 1972, use of DDT was severely In 1972, use of DDT was severely restricted in the United States, and the restricted in the United States, and the threatened bird populations slowly threatened bird populations slowly began to increase.began to increase.

United States still manufactures these United States still manufactures these pesticides and sends them to other pesticides and sends them to other countriescountries

Pesticide DDTPesticide DDT

In order for us to meet the needs of an In order for us to meet the needs of an increasingly crowded world, the use of increasingly crowded world, the use of chemicals is necessary, but we must chemicals is necessary, but we must learn to use them intelligently.learn to use them intelligently.

This will enable us to protect the This will enable us to protect the productive capacity of the Earth.productive capacity of the Earth.

Loss of ResourcesLoss of Resources Ecosystems are being damaged due to Ecosystems are being damaged due to

the consumption or destruction of the consumption or destruction of resources that we can not replace.resources that we can not replace.

Three kinds of nonrenewable resources Three kinds of nonrenewable resources are being consumed or destroyed at are being consumed or destroyed at alarming rates: species of living things, alarming rates: species of living things, topsoil, and ground water.topsoil, and ground water.

Extinction of SpeciesExtinction of Species Over the last 50 years, about half of the Over the last 50 years, about half of the

world’s tropical rain forests have been world’s tropical rain forests have been burned to make pasture and farmland and burned to make pasture and farmland and have been cut for timber.have been cut for timber.

The problem is that as the rain forests The problem is that as the rain forests disappear, so do their inhabitants and no disappear, so do their inhabitants and no one knows how many species are being one knows how many species are being lost.lost.

To find out, scientists carefully catalogue To find out, scientists carefully catalogue all of the residents of one small segment of all of the residents of one small segment of forest and then extrapolate their data.forest and then extrapolate their data.

It is estimated that we will lose up to one-It is estimated that we will lose up to one-fifth of the world’s species of plants and fifth of the world’s species of plants and animals during the next 50 years.animals during the next 50 years.

RainforestRainforest

The tragedy of extinction is that as The tragedy of extinction is that as species disappear, so do our chances to species disappear, so do our chances to learn about them and their possible learn about them and their possible benefits.benefits. ExampleExample: Rosy Periwinkle: Rosy Periwinkle Occurs naturally in MadagascarOccurs naturally in Madagascar Two potent anticancer drugs have Two potent anticancer drugs have

been isolated from the leaves of this been isolated from the leaves of this plantplant

Deforestation is threatening this Deforestation is threatening this species of plantspecies of plant

Loss of TopsoilLoss of Topsoil The United States is one of the most productive The United States is one of the most productive

agriculture countries on Earth, largely because of agriculture countries on Earth, largely because of its fertile soil.its fertile soil.

The topsoil has accumulated slowly as the The topsoil has accumulated slowly as the remains of countless animals and plants decayed.remains of countless animals and plants decayed.

By the time humans came to plow the land, the By the time humans came to plow the land, the topsoil was more than a meter thick.topsoil was more than a meter thick.

This rich topsoil cannot be replaced, and it is This rich topsoil cannot be replaced, and it is being lost at a rate of several centimeters each being lost at a rate of several centimeters each decade.decade.

Turning over the soil to eliminate weeds, allowing Turning over the soil to eliminate weeds, allowing animals to overgraze ranges and pastures, and animals to overgraze ranges and pastures, and practicing poor land management all permit wind practicing poor land management all permit wind and rain to remove more and more topsoil.and rain to remove more and more topsoil.

Since 1950, the world has lost one-third of it Since 1950, the world has lost one-third of it topsoil, primarily because of human activity.topsoil, primarily because of human activity.

TopsoilTopsoil

Ground-water Pollution and DepletionGround-water Pollution and Depletion Much ground water is stored within porous Much ground water is stored within porous

rock reservoirs called rock reservoirs called aquifersaquifers.. AquiferAquifer:: a porous rock that stores and a porous rock that stores and

allows the flow of ground waterallows the flow of ground water Water seeps into aquifers too slowly to Water seeps into aquifers too slowly to

replace the large amount of water now being replace the large amount of water now being withdrawn.withdrawn.

A very large portion of it is wasted on A very large portion of it is wasted on watering lawns, on washing cars, and watering lawns, on washing cars, and through leaky and inefficient faucets and through leaky and inefficient faucets and toilets.toilets.

Ground water is being polluted by Ground water is being polluted by irresponsible disposal of chemical wastes.irresponsible disposal of chemical wastes.

Once pollution enters the ground water, Once pollution enters the ground water, there is no effective way to remove it.there is no effective way to remove it.

AquiferAquifer

Growth of the Human PopulationGrowth of the Human Population In the very beginning, there were 5 million In the very beginning, there were 5 million

people on Earth.people on Earth. As agriculture produced more dependable As agriculture produced more dependable

sources of food, the human population began to sources of food, the human population began to grow.grow.

By 1650, the world’s population had reached 500 By 1650, the world’s population had reached 500 million.million.

The average global birthrate has remained near The average global birthrate has remained near 30 births per 1,000 people per year.30 births per 1,000 people per year.

However, with the development of technology to However, with the development of technology to ensure better sanitation and improved medical ensure better sanitation and improved medical care, the death rate has fallen steadily.care, the death rate has fallen steadily.

In 2002, the estimated death rate was about 9 In 2002, the estimated death rate was about 9 deaths per 1,000 people per year.deaths per 1,000 people per year.

The annual worldwide increase in human The annual worldwide increase in human population is approximately 1.3 percent.population is approximately 1.3 percent.

Growth of Human Growth of Human PopulationPopulation

Worldwide Rates of GrowthWorldwide Rates of Growth The world’s population exceeded 6 billion in The world’s population exceeded 6 billion in

October 1999, and the annual increase is October 1999, and the annual increase is now about 94 million.now about 94 million.

About 260,000 people are added to the world About 260,000 people are added to the world population each day, or about 180 every population each day, or about 180 every minute.minute.

Population growth is fastest in the Population growth is fastest in the developing countries of Asia, Africa, and developing countries of Asia, Africa, and Latin America.Latin America.

Population growth is the slowest in the Population growth is the slowest in the industrialized countries of North America, industrialized countries of North America, Europe, Japan, and in New Zealand, and Europe, Japan, and in New Zealand, and Australia.Australia.

The population growth rate in the United The population growth rate in the United States is only 0.8 percent.States is only 0.8 percent.

Population Growth Population Growth PatternsPatterns

The populations of Germany and Russia The populations of Germany and Russia are declining.are declining.

The global rate of population growth The global rate of population growth has been declining.has been declining.

The United Nations projects that the The United Nations projects that the world’s population will stabilize at 9.7 world’s population will stabilize at 9.7 billion by the year 2050.billion by the year 2050.

Population growth tends to be highest Population growth tends to be highest in countries that can least afford it.in countries that can least afford it.

Building a sustainable world is the most Building a sustainable world is the most important task facing humanity’s important task facing humanity’s future.future.

The quality of life available to your The quality of life available to your children in the new century will depend children in the new century will depend to a large extent on our success.to a large extent on our success.

C.C. Solving Environmental Solving Environmental ProblemsProblems

A Worldwide EffortA Worldwide Effort Environmental problems affect all Environmental problems affect all

inhabitants of an ecosystem without regard inhabitants of an ecosystem without regard to state or national boundaries.to state or national boundaries.

As human activities continue to place As human activities continue to place severe stresses on the ecosystems, severe stresses on the ecosystems, worldwide attention must be focused on worldwide attention must be focused on solving these problems.solving these problems.

A great deal of progress has been made in A great deal of progress has been made in reducing air and water pollution.reducing air and water pollution.

The number of secondary sewage treatment The number of secondary sewage treatment facilities, which remove chemicals as well facilities, which remove chemicals as well as bacteria from sewage, is on the increase.as bacteria from sewage, is on the increase.

““Scrubber” is a device that reduces Scrubber” is a device that reduces harmful sulfur emissions from industrial harmful sulfur emissions from industrial smokestacks.smokestacks.

Emissions of sulfur dioxide, carbon Emissions of sulfur dioxide, carbon monoxide, and soot, have been cut by monoxide, and soot, have been cut by more than 30 percent in 10 years.more than 30 percent in 10 years.

Serious attempts to address the overall Serious attempts to address the overall problem of pollution have also brought problem of pollution have also brought about more fundamental changes in our about more fundamental changes in our society.society. Example: CarpoolingExample: Carpooling

In the United StatesIn the United States Two effective approaches have been Two effective approaches have been

taken to reduce pollution in the United taken to reduce pollution in the United States.States.

The first approach has been to pass laws The first approach has been to pass laws forbidding it, which has slowed the forbidding it, which has slowed the spread of pollution.spread of pollution.

These laws impose strict standards for These laws impose strict standards for what can be released into the what can be released into the environment.environment.

Example: Laws Example: Laws Catalytic converters = reduce Catalytic converters = reduce

emissionsemissions Clean Air Act = requires scrubbers Clean Air Act = requires scrubbers

on the smokestackson the smokestacks

A second effective approach to reducing A second effective approach to reducing pollution has been to make it more pollution has been to make it more expensive by placing a tax on it.expensive by placing a tax on it.

Example: gasoline taxExample: gasoline tax By adjusting the tax, the government By adjusting the tax, the government

attempts to balance the confliction attempts to balance the confliction demands of environmental safety and demands of environmental safety and economic growth.economic growth.

Such taxes, often imposed on industry Such taxes, often imposed on industry in the form of “pollution permits”, are in the form of “pollution permits”, are becoming increasingly common.becoming increasingly common.

Solving Environmental ProblemsSolving Environmental Problems It is easy to get discouraged when It is easy to get discouraged when

considering the world’s many serious considering the world’s many serious environmental problems but each of the environmental problems but each of the world’s problems are solvable.world’s problems are solvable.

Five Steps to SuccessFive Steps to Success There are five components to successfully There are five components to successfully

solve any environmental problem:solve any environmental problem: AssessmentAssessment

Gather information about what is Gather information about what is happeninghappening

AnalyzeAnalyze Risk AnalysisRisk Analysis

Predict the consequences of different types Predict the consequences of different types of environmental interventionof environmental intervention

Also evaluate any negative effects Also evaluate any negative effects associated with a plan of action.associated with a plan of action.

Public educationPublic education Inform the publicInform the public Explain the problem wellExplain the problem well

Political actionPolitical action VoteVote Contact elected officialsContact elected officials

Follow-throughFollow-through Monitor to see if environmental Monitor to see if environmental

problem is being solved.problem is being solved.

Two Success StoresTwo Success Stores Example: Nashua RiverExample: Nashua River

Nashua River was severely polluted Nashua River was severely polluted by mills in Massachusettsby mills in Massachusetts

Marion Stoddart organized the Marion Stoddart organized the Nashua River Cleanup Committee.Nashua River Cleanup Committee.

The citizen’s campaign contributed to The citizen’s campaign contributed to the passage of the Massachusetts the passage of the Massachusetts Clean Water Act of 1966 which Clean Water Act of 1966 which banned industrial dumping in the banned industrial dumping in the river.river.

The river has largely recovered.The river has largely recovered.

Example: Lake WashingtonExample: Lake Washington Sewage plants discharged their Sewage plants discharged their

treated outflow into the lake.treated outflow into the lake. Blue-green algae growing in the lake, Blue-green algae growing in the lake,

this algae requires an abundance of this algae requires an abundance of the nutrients nitrogen and the nutrients nitrogen and phosphorus to grow.phosphorus to grow.

Bacteria decomposing the dead algae Bacteria decomposing the dead algae would soon deplete the lake’s oxygen would soon deplete the lake’s oxygen and would kill all life in the lakeand would kill all life in the lake

In 1961, Lake Washington was In 1961, Lake Washington was cleaned upcleaned up

Today the Lake is healthy Today the Lake is healthy

Your ContributionYour Contribution Humans rely on the Earth’s ecosystems for Humans rely on the Earth’s ecosystems for

food and all of the other materials our food and all of the other materials our civilization depends on.civilization depends on.

Although solving the world’s environmental Although solving the world’s environmental problems will take the efforts of many people, problems will take the efforts of many people, including politicians, economists, and including politicians, economists, and engineers, the issues are largely biological.engineers, the issues are largely biological.

Your knowledge of ecology is the essential tool Your knowledge of ecology is the essential tool that you can contribute to the effort.that you can contribute to the effort.

You can save energy by walking, riding a You can save energy by walking, riding a bicycle, or taking public transportation to work bicycle, or taking public transportation to work or school.or school.

Newspaper, aluminum products, glass Newspaper, aluminum products, glass containers, and many plastic containers can be containers, and many plastic containers can be recycled.recycled.

Choices that you make in your day to day Choices that you make in your day to day activities can benefit the environment.activities can benefit the environment.