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Natural population size varies

biotic potential - characteristics of thespecies may make it easier for thepopulation to increase

environmental resistance - factors thatprevent the population from growing toolarge (and exceeding the available

resources)

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Population growth curves

J curve - the fastest (exponential) rate ofpopulation growth

J curve is the rate the population wouldincrease if these was no effect fromenvironmental resistance

S curve - environmental resistance bringsthe population size into balance with theavailable resources

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Carrying capacity

the number of individuals the environmentcan support on a long term basis withoutdestroying the resources that supply the

ecosystem

carrying capacity can change

example: agriculture has increased thecarrying capacity for food resources forhuman populations (for pest species too!)

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Carrying capacity

population sizein balance withavailability ofresources

uses resourcesat same ratethey arereplaced

doesn't depleteresources ordestroy habitat

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The dark orange color represents individualsremoved from the population by environmentalresistance - thus decreasing population growth

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Human population growth - J or S curve?

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Population Clock

how fast is the world's population growing?(right click, select "open hyperlink")

http://www.poodwaddle.com/worldclock.swf

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Total Fertility Rate

total fertilityrate (TFR)

average #

children perwoman

replacementTFR = about2.1

why?

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Population Calculations

1. growth rate (GR) = BR DR

2. percent growth rate

(GR / 1000) * 100* quick tip -just move the decimal

point one place to the left

3. doubling time (DT) = 70 / PGR

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TABLE 1-1. POPULATION COMPARISONS 2008Source: Population Reference Bureau. World Population Data Sheet. Washington, DC. 2008.

COUNTRYPOP

(millions)

PGR

2008

DT

(years)TFR

PERCENTBELOW AGE

15

PERCENTABOVE AGE

65

AVG

ANNUALINCOME

2006 ($)

World 6,625 1.2 58 2.7 27 7 9,940

Russia 142 - 0.5 ---- 1.3 15 14 11,620

Japan 128 0.0 ---- 1.3 14 21 33,730

France 62 0.4 175 2.0 18 16 32,130

Norway 4.7 0.4 175 1.9 19 15 43,920

China 1,318 0.5 140 1.6 20 8 7,730

Australia 21 0.6 117 1.8 20 13 31,860

U.S. 302 0.6 117 2.1 20 12 44,260

Iran 71 1.2 58 2.0 29 5 8,480

Brazil 189 1.4 50 2.3 28 6 8,800

India 1,132 1.6 44 2.9 33 5 3,800

Mexico 107 1.7 41 2.4 32 6 11,330

Bangladesh 149 1.9 37 3.0 33 4 2,340

Pakistan 169 2.3 30 4.1 40 4 2,500

Ethiopia 77 2.5 28 5.4 43 3 1,190

Nigeria 144 2.5 28 5.9 48 3 1,150

how do

changesin DTand TFRaffectstandard

of living?

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Education level has a strong influence on familysize in developing and developed countries

TFR

note: seeexamplesin the

followingtwo slides

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teen mothers - Lincoln HS

Lincoln, Nebraska

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Population Profiles - age distribution diagrams

can be shown in percentage of population or with actual

population numbers

Ni i

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broaderbase of the

pyramid(representsbirth rate),

the fasterthepopulationis growing

Nigeria

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approximaterectangleindicates zeropopulationgrowth

birth rate is

equal todeath rate

interestingnote: what

happens to thegender ratios inold age?

Germany

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Broad base fuels rapid population growth aschildren reach reproductive age