# Chapter 20

```Chapter 5
Population Ecology
Charateristics: geographical
distribution, density and growth
Population Density
 Measures
is
how crowded a population
Unit examples?
City vs Suburbs vs Rural
Population Distribution
 Three
main ways
– Clumped
– Random
– Uniform/Even
 Most
common? Rare?
Distribution patterns
Population Dynamics
 Birth
rate = number of births over
time
 Death rate = deaths over a period of
time
 Life expectancy = how long
individuals in pop. are expected to
live
– Take a guess: life expectancy for men
and women in United States
 Men
= 72 years
 Women = 76 years
Population Growth Rate
 Growth
rate= change in population
size over time
 Depends upon the following:
– Birth
– Death
– Immigration
– Emigration
Age Structures
Effects of AIDS on a Population
 What
is a rate?
 What is birth rate?
 What is death rate?
 What are two additional factors that
cause a population to increase?
Decrease?
 What does per capita or % annual
growth rate mean?
Growth Rate
 What
is a rate?
– Change over time
– In math terms = slope
 What
is birth rate? death rate?
– Number of births over a period of time
– Number of deaths over a period of time
Growth Rate
 Two
factors that increase population
growth
– Births
– Immigration
 Two
factors that decrease population
growth
– Deaths
– Emmigration
Growth rate

% GROWTH RATE? - takes into account
total growth (births and immigration)
minus decline (death and emmigration)
– Change in growth over time


Look at fig 5-14 on page 132
What does ZPG mean?
– Zero population growth

What years had the highest % growth
rate?
Concept Map
Section 5-1
Population
Growth
can be
Logistic
growth
Exponential
growth
characterized by
No limits on
growth
Unlimited
resources
represented by
Constant
growth rate
J-shaped
curve
characterized by
Limits on
growth
which cause a
Falling
growth rate
represented by
S-shaped
curve
Exponential Model for
Population Growth
 Says
that populations grow rapidly
after only a few generations
Logistic Model
 Populations
are limited by their
environment
 Any factor that limits population
growth is called a limiting factor
 Limiting factors include things like
food, habitat availability, water,
predators
Carrying Capacity (K)
 The
number of individuals the
environment can support over a long
period of time.
 This number is due to birth rates,
death rates, and limiting factors
Humans –
how long?
HW – CH 5 Study Guides due
Tues!

Section Outline
5–2 Limits to Growth
Section 5-2
A.
B.
1.
2.
3.
4.
C.
Limiting Factors
Density-Dependent Factors
Extinction
Competition
Predation
Parasitism and Disease
Density-Independent
Factors
Population Fluctuations
1.
Density-independent factors- reduce
population by the same proportion
regardless of population size; ex. Cold
winter effects the squirrel population
–
2.
It doesn’t matter the size of the population
Density-dependent factors- resource
limits due to increase in population
density; ex. Shortage of food due to too
many deer in the area causes some deer
to starve.
Fluctuations Change the Graph
Extinction
 What
if an organism went extinct?
 What would the graph look like?
 Very
vulnerable to extinction
 Why is that?
 Inbreeding
 Something bad happens in the
environment and too many die to
sustain the population
 Ex. Cheetahs, sea otters, CA
Condors, Siberian tigers
Figure 5-7 Wolf and Moose Populations
on Isle Royale
Section 5-2
60
2400
50
2000
40
1600
30
1200
20
800
10
400
0
1955 1960
0
1965
1970
1975
Moose
1980
Wolves
1985
1990
1995
Human Populations
Human Populations
 They
have exploded over the last
1000 years
 The death rates have decreased and
the birth rates have increased. This
makes the overall growth rate
increase.
 Do you think that this current human
population is sustainable?
 Do you think that we are way past
our carrying capacity and it will go
down?
Human Population Growth
Section 5-3
Industrial
Revolution
begins
Agriculture
begins
Plowing
and
irrigation
Bubonic
plague
```