Evolution of Populations Evolution Unit. Population What is a population? Number of Individuals of the Same Species that Live together in one area or.

Evolution Evolution of of

PopulatioPopulationsns

Evolution Unit

PopulationPopulationWhat is a population?

Number of Individuals of theSame Species thatLive together in one area or place

Factors That Control Factors That Control Population GrowthPopulation Growth

A population’s biotic potential is the size it would be if nothing stopped it.

Why don’t populations grow indefinitely?

Factors That ControlFactors That ControlPopulation GrowthPopulation Growth

What determines the population number of an ecosystem (or planet)?

(Think in terms the basics that plants, animals and ourselves need to survive.)

Factors That Control Factors That Control Population GrowthPopulation Growth

Populations don’t grow indefinitely because of Limiting Factors.

The major limiting factors are FWSS:– Food– Water– Shelter– Space

Factors That Control Factors That Control Population GrowthPopulation Growth

Carrying Capacity is the maximum number of individuals the environment can support.

Carrying capacity is closely associated with the availability of limiting factors.

Factors That Control Factors That Control Population GrowthPopulation Growth

Does carrying capacity for an area ever change? Why or why not?

??

carrying capacity

Population Growth Population Growth RateRate

Exponential “J” CurveExponential “J” CurveSome populations start slow and

then have a burst of growth.

This is called EXPONENTIAL growth.

What shape curve does it have?

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Po

pu

lati

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70

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Po

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Population Growth Population Growth RateRate

Exponential “J” CurveExponential “J” CurveWhat is the slow

almost flat growth called?

What is the fast almost straight up growth called?

Lag

Exponential

A

B

What is this curve What is this curve called?called?

What is this phase?

What is this phase?

B.

A.

Population Growth Population Growth RateRate

Logistic “S” CurveLogistic “S” CurveSome populations start slow, have

a burst of growth, then level off.

This is called LOGISTIC growth.

What shape is the curve?

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Time (in days)

Population

Population Growth Population Growth RateRate

Logistic “S” CurveLogistic “S” CurveLogistic curves have a lag phase

and an exponential phase.

Where are they on this graph?

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Population

A

B

C

D

Population Growth Population Growth RateRate

Logistic “S” CurveLogistic “S” CurveThe almost flat, slightly up/down

line is called stabilization.

What letter represents stabilization on the graph?

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Population

A

B

C

D

Population Growth Population Growth RateRate

Logistic “S” CurveLogistic “S” CurveWhat is carrying capacity?What letter represents it?

Why does the population stabilize at “A”?

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Population

A

B

C

D

Population Growth Population Growth RateRate

Logistic “S” CurveLogistic “S” CurveWhat will happen to a population if

it goes over the carrying capacity?

What will happen to a population if it drops under the carrying capacity?

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Population

KK carrying capacity

lag

exponential

stabilization

Population Growth Population Growth RateRate

Logistic “S” CurveLogistic “S” CurveWhat is this?

What is this?

What is this?

What is this?

Why does it rise and fall slightly?

A.

C.

B.

D.

Natural SelectionNatural Selectionand Populationsand Populations

Recall Darwin’sConcepts of Natural Selection

variation exists in all species organisms produce more offspring than

can survive competition for limited life resources survival of the fittest (most suited to the

environment) descent with modification

Natural SelectionNatural Selectionand Populationsand Populations

Relate variation and offspring production to the population at B and C.

Describe competition when the population reaches A.

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Population

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Natural SelectionNatural Selectionand Populationsand Populations

Relate survival of the fittest with the population at D.

Describe the population at D in terms of descent with modification and variation.

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Population

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Natural SelectionNatural Selectionand Populationsand Populations

Relate the five concepts of natural selection to Graph #3.

Variation Numbers increase Competition Survival of the

fittest Descent with

modification

Event C

Event B

Event D

Event A

HumanHuman PopulationPopulation

What kind of curve is world population growth?

Human PopulationHuman PopulationWhere is the lag phase?The exponential phase?

Human PopulationHuman Population

Where is the carrying capacity?

Human PopulationHuman Population

What historical event could have caused the dip at the arrow?

Human PopulationHuman PopulationConsider the Black Death Plague

as an environmental change.Describe the population after the

Black Death (yellow arrow) in terms of variation and survival of the fittest.

Human PopulationHuman PopulationWhy would the industrial revolution

cause a population increase?

(think in terms of FWSS and carrying capacity)

Human PopulationHuman Population

Where do we go from here?

Childrenper Woman:High 2.5Medium 2.0Low 1.6

Human PopulationHuman Population

What is the Earth’s carrying capacity?

When will we reach it?

Who will survive?

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

Works CitedWorks Cited

“Big Horn Sheep”, “Seabirds”. No date. Online Image. Free Stock Photos. June 15, 2004. <http://www.geekphilosopher.com/MainPage/bkgLinksPhotos.htm>