Chp 8 Miller

8/14/2019 Chp 8 Miller

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Chapter 8Chapter 8

Population EcologyPopulation Ecology


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Chapter Overview QuestionsChapter Overview Questions

What are the major characteristics of What are the major characteristics of populations?populations?How do populations respond to changes inHow do populations respond to changes inenvironmental conditions?environmental conditions?How do species differ in their reproductiveHow do species differ in their reproductivepatterns?patterns?


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Updates OnlineUpdates Online

The latest references for topics covered in this section can be found atThe latest references for topics covered in this section can be found atthe book companion website. Log in to the books e-resources page atthe book companion website. Log in to the books e-resources page atwww.thomsonedu.com to access InfoTrac articles.www.thomsonedu.com to access InfoTrac articles.

InfoTrac: One Hatchling at a Time.InfoTrac: One Hatchling at a Time. Brownsville Herald Brownsville Herald (Brownsville, TX), July 2, 2006.(Brownsville, TX), July 2, 2006.InfoTrac: Where the Cattle Herds Roam, Ideally in HarmonyInfoTrac: Where the Cattle Herds Roam, Ideally in HarmonyWith Their Neighbors. Jim Robbins.With Their Neighbors. Jim Robbins. The New York TimesThe New York Times ,,July 11, 2006 pF3(L).July 11, 2006 pF3(L).InfoTrac: A nudge for nature.InfoTrac: A nudge for nature. Milwaukee Journal Sentinel Milwaukee Journal Sentinel ,,July 10, 2006.July 10, 2006.Earth Island InstituteEarth Island InstituteEnvironmental Defense: Creating a ConservationEnvironmental Defense: Creating a ConservationCommunity inCommunity inOregons Williamette ValleyOregons Williamette Valley

Marine Bio: Habitat ConservationMarine Bio: Habitat Conservation


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They were over-They were over-

hunted to thehunted to thebrink of extinctionbrink of extinctionby the earlyby the early

1900s and are1900s and arenow making anow making acomeback.comeback.

Core Case Study:Core Case Study:Southern Sea Otters: Are They BackSouthern Sea Otters: Are They Back

from the Brink of Extinction?from the Brink of Extinction?

Figure 8-1Figure 8-1


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POPULATION DYNAMICS ANDPOPULATION DYNAMICS ANDCARRYING CAPACITYCARRYING CAPACITY

Most populations live in clumps although other Most populations live in clumps although other patterns occur based on resource distribution.patterns occur based on resource distribution.



7/36Fig. 8-2a, p. 162(a) Clumped (elephants)


8/36Fig. 8-2b, p. 162(b) Uniform (creosote bush)


9/36Fig. 8-2c, p. 162(c) Random (dandelions)


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Changes in Population Size:Changes in Population Size:Entrances and ExitsEntrances and Exits

Populations increase through births andPopulations increase through births andimmigrationimmigration

Populations decrease through deaths andPopulations decrease through deaths andemigrationemigration


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Age Structure: Young PopulationsAge Structure: Young Populations

Can Grow FastCan Grow FastHow fast a population grows or declines dependsHow fast a population grows or declines dependson its age structure.on its age structure.

Prereproductive agePrereproductive age : not mature enough to: not mature enough toreproduce.reproduce.Reproductive ageReproductive age : those capable of reproduction.: those capable of reproduction.Postreproductive agePostreproductive age : those too old to reproduce.: those too old to reproduce.


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Limits on Population Growth:Limits on Population Growth:Biotic Potential vs. EnvironmentalBiotic Potential vs. Environmental

ResistanceResistanceNo population can increase its sizeNo population can increase its size

indefinitely.indefinitely.The intrinsic rate of increase (The intrinsic rate of increase ( r r ) is the rate at) is the rate atwhich a population would grow if it had unlimitedwhich a population would grow if it had unlimitedresources.resources.Carrying capacity (Carrying capacity ( K K ): the maximum population): the maximum populationof a given species that a particular habitat canof a given species that a particular habitat cansustain indefinitely without degrading the habitat.sustain indefinitely without degrading the habitat.


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Exponential and Logistic PopulationExponential and Logistic PopulationGrowth: J-Curves and S-CurvesGrowth: J-Curves and S-Curves

Populations growPopulations growrapidly with amplerapidly with ampleresources, but asresources, but as

resources becomeresources becomelimited, its growthlimited, its growthrate slows andrate slows andlevels off.levels off.



14/36Fig. 8-3, p. 163

EnvironmentalResistance

Time (t)

( N )

Carrying capacity (K)

ExponentialGrowth

BioticPotential


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Exponential and Logistic PopulationExponential and Logistic PopulationGrowth: J-Curves and S-CurvesGrowth: J-Curves and S-Curves

As a populationAs a populationlevels off, itlevels off, itoften fluctuatesoften fluctuatesslightly aboveslightly aboveand below theand below thecarryingcarryingcapacity.capacity.



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Carrying capacity

Year

Numberofsheep(millions)

Overshoot


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Exceeding Carrying Capacity: Move,Exceeding Carrying Capacity: Move,Switch Habits, or Decline in SizeSwitch Habits, or Decline in Size

Members of Members of populations whichpopulations which

exceed their exceed their resources will dieresources will dieunless they adapt or unless they adapt or

move to an area withmove to an area withmore resources.more resources.



18/36Fig. 8-6, p. 165

Numberofreindeer

Populationovershootscarryingcapacity

Carrying

capacity

Year

PopulationCrashes


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Exceeding Carrying Capacity: Move,Exceeding Carrying Capacity: Move,Switch Habits, or Decline in SizeSwitch Habits, or Decline in Size

Over time species may increase their Over time species may increase their carrying capacity by developing adaptations.carrying capacity by developing adaptations.

Some species maintain their carryingSome species maintain their carryingcapacity by migrating to other areas.capacity by migrating to other areas.So far, technological, social, and other So far, technological, social, and other

cultural changes have extended the earthscultural changes have extended the earthscarrying capacity for humans.carrying capacity for humans.


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How Would You Vote?How Would You Vote?

To conduct an instant in-class survey using a classroom responseTo conduct an instant in-class survey using a classroom responsesystem, access JoinIn Clicker Content from the PowerLecture mainsystem, access JoinIn Clicker Content from the PowerLecture mainmenu for Living in the Environment.menu for Living in the Environment.

Can we continue to expand the earth'sCan we continue to expand the earth'scarrying capacity for humans?carrying capacity for humans?a. No. Unless humans voluntarily control their a. No. Unless humans voluntarily control their population and conserve resources, nature willpopulation and conserve resources, nature will

do it for us.do it for us.b. Yes. New technologies and strategies willb. Yes. New technologies and strategies willallow us to further delay exceeding the earth'sallow us to further delay exceeding the earth'scarrying capacity.carrying capacity.


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Population Density and PopulationPopulation Density and PopulationChange: Effects of CrowdingChange: Effects of Crowding

Population density: the number of individualsPopulation density: the number of individualsin a population found in a particular area or in a population found in a particular area or

volume.volume.A populations density can affect how rapidly itA populations density can affect how rapidly itcan grow or decline.can grow or decline.

e.g. biotic factors like diseasee.g. biotic factors like disease

Some population control factors are not affectedSome population control factors are not affectedby population density.by population density.

e.g. abiotic factors like weather e.g. abiotic factors like weather


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Types of Population ChangeTypes of Population ChangeCurves in NatureCurves in Nature

Population sizes may stay the same, increase,Population sizes may stay the same, increase,decrease, vary in regular cycles, or changedecrease, vary in regular cycles, or changeerratically.erratically.

StableStable : fluctuates slightly above and below carrying: fluctuates slightly above and below carryingcapacity.capacity.IrruptiveIrruptive : populations explode and then crash to a more: populations explode and then crash to a morestable level.stable level.

Cyclic Cyclic : populations fluctuate and regular cyclic or : populations fluctuate and regular cyclic or boom-and-bust cycles.boom-and-bust cycles.Irregular Irregular : erratic changes possibly due to chaos or : erratic changes possibly due to chaos or drastic change.drastic change.


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Types of Population ChangeTypes of Population ChangeCurves in NatureCurves in Nature

Population sizes often vary in regular cyclesPopulation sizes often vary in regular cycleswhen the predator and prey populations arewhen the predator and prey populations arecontrolled by the scarcity of resources.controlled by the scarcity of resources.



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Fig. 8-7, p. 166

Populationsize(thousands)

Year

LynxHare


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Case Study: Exploding White-TailedCase Study: Exploding White-TailedDeer Populations in the United StatesDeer Populations in the United States

Since the 1930s the white-tailed deer Since the 1930s the white-tailed deer population has exploded in the United States.population has exploded in the United States.

Nearly extinct prior to their protection in 1920s.Nearly extinct prior to their protection in 1920s.

Today 25-30 million white-tailed deer in U.S.Today 25-30 million white-tailed deer in U.S.pose human interaction problems.pose human interaction problems.

Deer-vehicle collisions (1.5 million per year).Deer-vehicle collisions (1.5 million per year).Transmit disease (Lyme disease in deer ticks).Transmit disease (Lyme disease in deer ticks).


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REPRODUCTIVE PATTERNSREPRODUCTIVE PATTERNS

Some species reproduce without having sexSome species reproduce without having sex(asexual).(asexual).

Offspring are exact genetic copies (clones).Offspring are exact genetic copies (clones).

Others reproduce by having sex (sexual).Others reproduce by having sex (sexual).Genetic material is mixture of two individuals.Genetic material is mixture of two individuals.Disadvantages: males do not give birth, increaseDisadvantages: males do not give birth, increase

chance of genetic errors and defects, courtshipchance of genetic errors and defects, courtshipand mating rituals can be costly.and mating rituals can be costly.Major advantages: genetic diversity, offspringMajor advantages: genetic diversity, offspringprotection.protection.


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Sexual Reproduction: CourtshipSexual Reproduction: Courtship

Courtship ritualsCourtship ritualsconsume time andconsume time andenergy, can transmitenergy, can transmit

disease, and candisease, and caninflict injury on malesinflict injury on malesof some species asof some species asthey compete for they compete for sexual partners.sexual partners.



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Reproductive Patterns:Reproductive Patterns:

Opportunists and CompetitorsOpportunists and CompetitorsLarge number of Large number of smaller offspring withsmaller offspring with

little parental care (r-little parental care (r-selected species).selected species).Fewer, larger offspringFewer, larger offspringwith higher investedwith higher investedparental care (K-parental care (K-selected species).selected species).



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Fig. 8-9, p. 168

r species;experiencer selection

Time

K Carrying capacity

K species;experienceK selection


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Reproductive PatternsReproductive Patterns

r-selected species tend to be opportunistsr-selected species tend to be opportunistswhile K-selected species tend to bewhile K-selected species tend to be

competitors.competitors. Figure 8-10Figure 8-10


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Fig. 8-10a, p. 168

Many small offspring

Little or no parental care and protection of offspring

Early reproductive age

Most offspring die before reaching reproductive age

Small adults

Adapted to unstable climate and environmentalconditions

High population growth rate (r)

Population size fluctuates wildly above and belowcarrying capacity (K)

Generalist niche

Low ability to compete

Early successional species

r-Selected SpeciesCockroach

Dandelion


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Fig. 8-10b, p. 168

Fewer, larger offspring

High parental care and protectionof offspring

Later reproductive age

Most offspring survive to reproductive ageLarger adults

Adapted to stable climate and environmentalconditions

Lower population growth rate (r)

Population size fairly stable and usually close tocarrying capacity (K)

Specialist niche

High ability to compete

Late successional species

K-Selected Species

SaguaroElephant


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Survivorship Curves:Survivorship Curves:Short to Long LivesShort to Long Lives

The way to represent the age structure of aThe way to represent the age structure of apopulation is with apopulation is with a survivorship curvesurvivorship curve ..

Late loss populationLate loss population live to an old age.live to an old age.Constant loss populationConstant loss population die at all ages.die at all ages.Most members of Most members of early loss populationearly loss population , die at, die atyoung ages.young ages.


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Survivorship Curves:Survivorship Curves:Short to Long LivesShort to Long Lives

The populationsThe populationsof differentof differentspecies vary inspecies vary inhow longhow longindividualindividualmembersmemberstypically live.typically live.



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P e r c e n

t a g e s u r v

i v i n g

( l o g s c a

l e )

A

Early loss

Late loss

C o n s t a n t l o s s

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