1. Objectives
Explain the characteristics used to describe a population.
Explain factors that affect population size.
Explain exponential and logistic growth.
Define the following:
A. Population density
B. Immigration
C. Emigration
D. Carrying capacity

2. Characteristics of Populations
Geographic distribution – the area inhabited by a population
Density – number of individuals per unit area
Growth rate
Age structure
Math Connections
Population density = Number of Individuals/Unit area

3. Suppose there are 150 bullfrogs living in a pond that covers an area of 3 square kilometers. What is the density of the bullfrog population?
150 divided by 3 = 50 bullfrogs per square kilometer

4. Factors that Affect Population Size
Number of births
Number of deaths
Number of individuals that enter or leave the population
A. Immigration – movement of individuals into an area
B. Emigration – movement of individuals out of a population

5. Population Growth
Exponential Growth
A. Occurs under ideal conditions with unlimited resources
(Abundance of food, water, and shelter; absence of predation and
disease)
B. Population reproduces at a constant rate
Logistic Growth
A. Occurs when a population’s growth slows or stops following a period
of exponential growth
B. Resources become less available

6. Carrying Capacity
Carrying capacity is the largest number of individuals that a given environment can support.
What is the growth rate if a particular species reaches its carrying capacity in a given environment?

7. Concept Map Population Growth Logistic Exponential growth Limits on
Section 5-1
Population
Growth
can be
Exponential
growth
Logistic
characterized by
represented by
characterized by
represented by
Falling
growth rate
S-shaped
curve
Limits on
growth
No limits on
J-shaped
Constant
Unlimited
resources
which cause a
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8. Figure 5-4 Logistic Growth of Yeast Population
Section 5-1
Carrying capacity
Number of Yeast Cells
Time (hours)
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9. Interest Grabber Name That Resource!
Section 5-2
Name That Resource!
A situation that causes the growth of a population to decrease is called a limiting factor. Some limiting factors depend on the size of the population. Other limiting factors affect all populations in similar ways, regardless of the population size.
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10. Interest Grabber continued
Section 5-2
1. Imagine a small island that has a population of five rabbits. How might
each of the following factors affect the rabbit population?
a. climate
b. food supply
c. predation
2. Now imagine another small island that has a population of 500 rabbits.
How would the same factors affect this population?
3. Which of the factors depend on population size? Which factors do not depend on population size?
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11. Name that Resource! 1. All of these factors could limit this population. The food supply would have to dwindle substantially in order for it to affect only five rabbits. One predator could wipe out the entire population of five rabbits. 2. Predation and the availability of food will have more of an effect on this population than the smaller one because there are more rabbits to be preyed upon and to compete for the food. 3. The factors that depend on population size include the competition for food and predation. The factor that does not depend on population size is climate.

12. Objectives
Explain factors that limit population growth.
Define the following:
A. Limiting factor
B. Density-dependent limiting factor
C. Predator-prey relationship
D. Density-independent limiting factor

13. Section Outline Limits to Growth
Density-Dependent Factors – depend on population size
1. Competition – Crowded; organisms struggle with one another for
food, water, space, sunlight, and other essentials of life
Note: Competition can also occur between members of
different species. This type of competition is a major
force behind evolutionary change.
2. Predation (Examples: relationships between sea otters and sea
urchins and sea otters and killer whales)
3. Parasitism and Disease
Density-Independent Factors – unusual weather, natural disasters, seasonal cycles, certain human activities
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14. A Density-Dependent Limiting Factor
Section 5-2
Growth of Aphids
Exponential growth
Peak population
size
Rapid decline
Steady population
size
Steady population
size
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15. 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
1955
1960
1965
1970
1975
1980
1985
1990
1995
Moose
Wolves
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16. Wolf and Moose
What density-dependent factors may have caused the crash in the wolf population?
Decline in the moose population
What density-independent factors may have caused the crash in the wolf population?
Unusually deep winter snows could have made it difficult for the wolf to hunt, parasites or disease could have weakened or killed the wolves
How are the increases and decreases in the moose population related to changes in the wolf population?
As the moose population increased, the wolf population increased.
Decreases in the moose population were followed by decreases in the wolf population.

17. Interest Grabber How Fast Are We Growing?
Section 5-3
How Fast Are We Growing?
Until about 500 years ago, the world’s human population remained fairly stable. Then, as advances in medicine, agriculture, and technology occurred, the human population began growing very rapidly. Today, the world’s human population is greater than 6 billion people, and it continues to grow, but at a slower rate.
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18. Objectives
Describe how the size of the human population has changed over time.
Explain why population growth rates differ in countries throughout the world.
Define the following:
A. Demography
B. Demographic Transition
C. Age-structure diagram

19. Demography – the scientific study of human populations
Demographic transition – change in a population from high birth and death rates to low birth and death rates
Age-structure diagram – graphs that represent the numbers of people in different age groups in a population

20. Human Population Growth
Section 5-3
Industrial
Revolution
begins
Agriculture
begins
Bubonic
plague
Plowing
and
irrigation
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21. Important People:
Dr. Leila Denmark – oldest practicing physician in the United States;
helped invent the whooping cough vaccine in 1936
Connections to Economics:
Two centuries ago, English economist Thomas Malthus observed that human populations were growing rapidly. He predicted that such growth would not continue indefinitely. According to Malthus, famine and disease would limit human population growth.
Today, scientists have identified a variety of other social and economic factors that can affect human populations.

22. Figure 5-13 Age Distribution
Section 5-3
U.S. Population
Rwandan Population
Males
Females
Males
Females
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23. How do the United States and Rwanda differ in the percentages of 10-14 year olds in the population?
In the United States, year olds make up about 6.5% of the population, and in Rwanda they make up about 14% of the population. The difference is about 7.5% - about 3.5 percentage points for males and 4 percentage points for females.