Population Growth
Dynamic biological processes influence population
density, dispersion, and demographics
• A population is a group of individuals of a
single species living in the same general area
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Density and Dispersion
• Density is the number of individuals per unit
area or volume
• Dispersion is the pattern of spacing among
individuals within the boundaries of the
population
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Population Growth
• Biotic potential is the maximum reproductive
capacity which when be plotted as Theoretical
population growth which can be called a Jcurve
• Environmental resistance includes all
limiting factors that prevent biotic potential
from being attained
• Realized population growth is the actual
growth of a population and when plotted is
often called an S-curve
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Population Change and Population Density
• In density-independent factors: exert the
same effect regardless of population size.
• In density-dependent factors: the effects
increase as population increases
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
1350
1300
1250
1200
1150
1100
1050
1000
950
900
850
800
750
700
650
600
550
500
450
400
350
300
250
200
150
100
50
0
Environmental
resistance
Theoretical
Realized
4
1
1.
2.
3.
4.
5.
3
2
1
2
3
5
4
5
6
7
8
9
10
11
Lag phase-due to small number of organisms
Exponential growth phase-periodic doubling of populations
Inflection point-start of decreasing growth phase
Decreasing growth phase-curve makes a right turn
Carrying capacity-population size in balance with the environment
12
Growth Rate
Birth Rate-Death Rate/1000 people
Convert to % move decimal over
DOUBLING TIME=Time required for a population to double in size
Determined by dividing 70 years (demographic constant) by growth rate