Copyright © 2005 Pearson Prentice Hall, Inc. Chapter 39 Population Growth and Regulation.
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Copyright © 2005 Pearson Prentice Hall, Inc.
Chapter 39
• Population Growth and Regulation
Copyright © 2005 Pearson Prentice Hall, Inc.
How Does Population Size Change?
• Biotic Potential Can Produce Exponential Growth– Exponential growth curves are J-shaped (F39.1 p.
800) – The effect of death rates on population growth
(F39.2 p. 801)
number of individuals time (minutes)
time (years)
Reproduction begins at 6 years
bacteria
eagles(i)
(ii)
time number of (minutes) bacteria
0 120 240 460 880 16
100 32120 64140 128160 256180 512200 1024220 2048
time number of number of(years) eagles (i) eagles (ii)
0 2 22 2 24 4 26 8 48 14 8
10 28 1212 52 1614 100 3216 190 5418 362 8620 630 14222 1314 23824 2504 39226 4770 64428 9088 106630 17314 1764
number of individuals
time (minutes)
bacteria
time number of (minutes) bacteria
0 120 240 460 880 16
100 32120 64140 128160 256180 512200 1024220 2048
number of individuals
time (years)
Reproduction begins at 6 years
time number of number of(years) eagles (i) eagles (ii)
0 2 22 2 24 4 26 8 48 14 8
10 28 1212 52 1614 100 3216 190 5418 362 8620 630 14222 1314 23824 2504 39226 4770 64428 9088 106630 17314 1764
(i)
(ii)
number of individuals
time (years)
Reproduction begins at 6 years
time number of number of(years) eagles (i) eagles (ii)
0 2 22 2 24 4 26 8 48 14 8
10 28 1212 52 1614 100 3216 190 5418 362 8620 630 14222 1314 23824 2504 39226 4770 64428 9088 106630 17314 1764
(i)
(ii)
no deaths
number of individuals
time (hours)
bacteria
10% die between doublings
25% die between doublings
Copyright © 2005 Pearson Prentice Hall, Inc.
How Is Population Growth Regulated?
• Exponential Growth Cannot Continue Indefinitely– A boom-and-bust population cycle (F39.3 p. 801) – Lemming population cycles follow a boom-
and-bust pattern (F39.4 p. 801)
population density
approximate number of lemmings per acre
Copyright © 2005 Pearson Prentice Hall, Inc.
How Is Population Growth Regulated?
• Environmental Resistance Limits Population Growth– The S-curve of population growth (F39.5 p. 803)
– The effects of exceeding carrying capacity (F39.6
p. 804)
carrying capacity
time
exponentialgrowth: J-curve
(environmental resistance)
equilibrium(bioticpotential)
num
ber
of i n
divi
dua l
s
exponentialgrowth
populationcrash
year
num
ber
of r
eind
eer
0
500
1000
1500
2000
1910 1920 1930 19501940
Copyright © 2005 Pearson Prentice Hall, Inc.
How Is Population Growth Regulated?
– Density-Independent Factors Limit Populations Regardless of Their Density
– Density-Dependent Factors Become More Effective as Population Density Increases
– Predators and Parasites Exert Density-Dependent Controls on Populations
• Predators help control prey populations (F39.7 p. 805)
Copyright © 2005 Pearson Prentice Hall, Inc.
How Is Population Growth Regulated?
– Competition for Resources Helps Control Populations
• Emigration (F39.8 p. 806)
Copyright © 2005 Pearson Prentice Hall, Inc.
How Is Population Growth Regulated?
• Survivorship in Populations Follows Three Basic Patterns– Survivorship curves (F39.9 p. 807)
1000
100
10
0
num
ber
of s
urvi
vors
age(in percentage of maximum life span)
early loss(dandelion)
constant loss(American robin)
late loss(human)
Copyright © 2005 Pearson Prentice Hall, Inc.
How Is the Human Population Changing?
• The Human Population Is Growing Rapidly– Human population growth (F39.10 p. 808)
Technical and cultural advances Agricultural advances Industrial andmedicaladvances
bubo
nic
plag
ue
bil li
ons
of p
eopl
e
7
6
5
4
3
2
1
0
20031999
1987
1975
1960
1930
1830
12,000 11,000 10,000 9000 8000 7000 6000 5000 4000 3000 2000 1000 B.C./A.D. 1000 2000 B.C. B.C. B.C. B.C. B.C. B.C. B.C. B.C. B.C. B.C. B.C. B.C. A.D. A.D.
Copyright © 2005 Pearson Prentice Hall, Inc.
How Is the Human Population Changing?
• Technological Advances Have Increased Earth’s Carrying Capacity for Humans– Unnumbered Figure 1 (p. 809) – Unnumbered Figure 2 (p. 809)
time
death rate
naturalincrease
birth rate
Demographic transition
birt
h an
d de
ath
rate
2003: 6.3 billion
developing countries
developed countries
10
8
6
4
2
0
po
pu
latio
n (
bill
ion
s)
1950 1970 1990 2010 2030 2050
Copyright © 2005 Pearson Prentice Hall, Inc.
How Is the Human Population Changing?
• The Age Structure of a Population Predicts Its Future Growth (F 3 p. 810) – Age structures compared (F39.11 p. 810) – Population change by world regions (F39.12 p.
811)
expanding stable shrinking
postreproductive(46–100 years)
reproductive(15–45 years)prereproductive(0–14 years)
Developed countries 2003 2025
postreproductive (45–79 yr)
reproductive (15–44 yr)
prereproductive (0–14 yr)
millions of people
millions of people
age
age
Developing countries
(a)
(b)
80
70
60
50
40
30
20
10
0
80
70
60
50
40
30
20
10
0
320 280 240 200 160 120 80 40 0 40 80 120 160 200 240 280 320
320 280 240 200 160 120 80 40 0 40 80 120 160 200 240 280 320
World average 1.3%
Developing countries 1.6%
World regions
annual natural increase
Africa 2.4%
Latin America/Caribbean 1.7%
Asia (excluding China and Japan) 1.6%
Developed countries 0.1%
China 0.6%
N. America 0.5%
Europe –0.2%
Copyright © 2005 Pearson Prentice Hall, Inc.
How Is the Human Population Changing?
• The United States Population Is Growing Rapidly– U.S. population growth (F39.13 p. 812)
– Population cycles in predators and prey (FE39.1 p. 802) – Experimental predator–prey cycles (F E39.2 p. 802)
– Deforestation can lead to the loss of productive land (FE39.3 p. 813)
U.S. population (in millions)(1790–2003)
year
abundance of lynx ( 1000)
abundance of hares ( 1000)
year
hares (prey)lynx (predator)
adult population
generation
bean weevils (prey)
branconid wasp (predator)
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