1. No category

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Chapter 5 Populations
Population Size
Population size is the number of individuals that make up a
population. Immigration and births increase population size.
Emmigration and deaths decrease population size.
The table below shows how several different populations have changed
over a one-year time span. Look at each population and determine
whether the overall population size has increased or decreased. If the
population size has increased, draw an arrow that points upward
(!) in the population size column. If it has decreased, draw an
arrow that points downward ("). The first one has been done for you.
Factors that Affect Population Size
Population
Births
Deaths
Number of
Individuals
that
Emigrated
A
200
100
0
0
B
10
10
100
0
C
1
1
1
50
D
10
100
100
10
E
100
200
0
0
F
50
1
1
50
G
10
10
0
100
Section 5–1 How Populations Grow
(pages 119–123)
This section identifies the characteristics used to describe a population. It
also describes factors that affect population size and explains what
exponential growth and logistic growth are.
Characteristics of Populations
(page 119)
1. What are the four main characteristics of a population?
a. Geographic distribution
c. Growth rate
b. Density
d. Age structure
2. What is a population’s geographic distribution? It is the area inhabited by the population.
range
.
4. What is population density? It is the number of individuals per unit area.
3. Another term for geographic distribution is
Number of
Individuals
that
Immigrated
Population
Size
!
of individuals
Population density = Number
Unit area
Population Growth
(page 120)
6. Circle the letter of each sentence that is true about populations.
a. They can grow rapidly.
b. They can decrease in size.
c. They may stay the same size from year to year.
d. They stay the same size until they disappear.
7. What three factors can affect population size?
a. The number of births
b. The number of deaths
c. The number of individuals that enter or leave the population
8. If more individuals are born than die in any period of time, how will the population
change? It will grow.
9. Complete the table about changes in population.
2. A food shortage causes many members of a population to leave
an area. What type of population movement does this describe?
Circle the correct answer.
emigration
immigration
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45
CHANGES IN POPULATION
Type of Change
Definition
Resulting Change in Size
Immigration
The movement of individuals into an area
The population grows
Emigration
The movement of individuals out of an area
The population decreases
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Use the table to answer the question.
1. Look at population G. How would the population size have
changed if 100 individuals had also emigrated?
5. What is the equation with which you can calculate population density?
Population Growth
Model 3 – Growth Curves
Diagram A—Exponential Growth Curve
How is population growth naturally regulated?
Diagram B—Logistic Growth Curve
Why?
The current world population is estimated to be over 7 billion. At present the number of births annually
exceeds the number of deaths, which means that the population is increasing, and is estimated to reach
9 billion by 2040. In 1750 the world population was estimated at less than 800 million. How are growing
populations such as ours controlled and supported, and can they continue to grow indefinitely?
B)
Lag phase
Total Population
s
ath
De
)
(D
Exponential
growth
Time
Em
igr
ati
on
Population Numbers
(I)
on
ati
s(
m
igr
rth
Im
Bi
Population Numbers
Model 1 – Population Growth
Carrying
capacity (K)
Pressure begins due to
environmental resistance
Lag phase
Time
9. Refer to Model 3.
(E
a. During what phase of the growth curves in each diagram is the population just beginning to
colonize an area?
)
b. Which type of population growth appears to continue unchecked?
1. Refer to Model 1.
a. What is the term used for populations moving into an area?
b. What is the term used for populations leaving an area?
10. The growth curves in Model 3 are often referred to using the letters of the alphabet they resemble. The logistic growth curve is sometimes referred to as an S-curve. What letter would you use
to describe the exponential growth curve?
c. Name two factors that cause an increase in the population size.
11. What causes the population to slow down during logistic growth?
d. Name two factors that cause a decrease in population size.
12. The maximum population an environment can sustain is affected by environmental factors that
cause the population to level out or become stable. What term is used to describe this level of
logistic growth?
Population Growth
1
4
POGIL™ Activities for High School Biology
13. Propose some reasons why population growth is so rapid immediately after the lag phase in both
diagrams of Model 3?
14. Exponential growth (diagram A) refers to the phenomena of populations that double in size
every generation. If you start with a single bacterium capable of dividing every 20 minutes, how
many bacteria would you have after just four hours?
15. In most natural populations rapid exponential growth is unsustainable. As populations increase,
environmental resistance causes the growth rate to slow down, until carrying capacity is reached.
With your group, brainstorm several factors that could be considered as environmental resistance.
16. Diagram B shows that the population size fluctuates around the carrying capacity. Considering what you know about interactions in the environment, discuss with your group some of the
factors that could cause these fluctuations. In your answer you should relate these factors to the
information from Model 1.
Population Growth
5
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Exponential Growth
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(page 121)
10. How will a population change if there is abundant space and food and if the population
is protected from predators and disease? The population will multiply, and the population size
will increase.
11. When does exponential growth occur? It occurs when individuals in a population reproduce
at a constant rate.
12. What are three ways that a growth rate may be stated, or expressed? It may be stated as a
doubling time, a birthrate per female, or a percentage of growth per year.
13. Under ideal conditions with unlimited resources, how will a population grow?
Such a population would grow exponentially.
18. When does logistic growth occur? It occurs when a population’s growth slows or stops
following a period of exponential growth.
19. Circle the letter of each instance when a population’s growth will slow down.
a. The birthrate and death rate are the same.
b. The birthrate is greater than the death rate.
c. The rate of immigration is equal to the rate of emigration.
d. The rate of emigration is less than the rate of immigration.
20. What is the carrying capacity of the environment for a particular species?
It is the largest number of individuals that the given environment can support.
14. Complete the graph by drawing the characteristic shape of exponential population
growth.
21. Complete the graph by drawing the characteristic shape of logistic population growth.
Exponential Growth of Bacterial Population
Logistic Growth of Yeast Population
300,000
Number of Yeast Cells
Number of Bacteria
Carrying capacity
200,000
100,000
0
0
2
4
6
15. Is the following sentence true or false? Elephants never grow exponentially because
their rate of reproduction is so slow.
Logistic Growth
false
(page 122)
16. Circle each sentence that is true about exponential growth.
a. It continues until the organism covers the planet.
b. It continues at the same rate as resources become less available.
c. It does not continue in natural populations for very long.
d. It continues in natural populations until the birthrate increases.
17. When resources become less available, how does population growth change?
It slows or stops.
Time (hours)
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Time (hours)
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Name
Date __________
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Date
Chapter 5 Populations
Density-Dependent and Density-Independent
Limiting Factors
Density-dependent limiting factors limit a population when the
population density reaches a certain level. Density-independent
limiting factors affect a population in the same way no matter how
big or small it is.
Read the information in the table.
Limiting
Factor
Brief Description of
the Limiting Factor
Extreme
Climate
Changes
Drought and other extreme climate
changes can cause members of a
population to die off rapidly.
Competition
Individuals of the same species compete
with each other for resources.
Human
Disturbances
Graphic Organizer
Concept Map
Using information from the chapter, complete the concept map below. If there is
not enough room in the concept map to write your answers, write them on a
separate sheet of paper.
Population Limiting
Factors
include
1.
2.
Human activity, like damming a river, can
harm many populations in an ecosystem.
Parasites limit the growth of a population
by taking nourishment from their hosts.
In the spaces provided, label each limiting factor as either densitydependent or density-independent.
Extreme climate changes
Competition
Human disturbances
Parasitism
Use the table to answer the question.
1. Give another example of an extreme climate change that might
limit the growth of a population.
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48
affect
populations
3.
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Parasitism
affect
populations
4.
examples include
Competition
5.
7.
Teaching Resources /Chapter 5
examples
include
Parasitism
Natural
disasters
6.
8.
Human
activities
61
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Predator-Prey Relationships
A predator is an animal that eats other animals. Prey is the animal
that gets eaten. Predator-prey interactions can affect the population growth of both the predator and the prey. In the graph below,
the wolves are the predators and the moose are the prey.
Follow the prompts to help you analyze the graph.
• Circle the part of the line representing the moose population
from the years 1964 to 1974 in red.
• Circle the part of the line representing the wolf population
from the years 1969 to 1980 in blue.
2400
50
2000
40
1600
30
1200
20
800
10
400
0
1955
0
1960
1965
1970
1975
1980
1985
1990
1995
Year
Wolves
Moose
Use the graph to answer the questions.
1. Was the moose population increasing or decreasing from
1964 to 1974?
2. Was the wolf population increasing or decreasing from
1969 to 1980?
3. Why might changes in the moose population from 1964 to 1974
relate to changes in the wolf population from 1969 to 1980?
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49
Number of Moose
Number of Wolves
Wolf and Moose Populations on Isle Royale
60