Populotion Growth
Name
Partner
Section
Date
Four rates - natality, mortality, immigration, and emigration - determine a population's size. A given area can
support only a certain number of individuals on a long-term basis. That number is known as the carrying capacity.
Populations grow at different rates; the doubling time is the number of years required for a particular population to
double its size. In this investigation, you will compare the growth of two populations and examine the roles played
by carrying capacify, doubling time, and the four rates that determine a population's size.
Part A: Reindeer Population
Procedure
l. In l9l l, 25 reindeer - 4 males
and 2l females - were introduced into St. Paul Island, one of the Pribilof
Islands in the Bearing Sea near Alaska. St. Paul Island is approximately 106 km2 in size (4 1 square miles),
and is more than 323 km (200 miles) from the mainland. On St. Paul Island, there were no predators of the
reindeer and no hunting of the reindeer was allowed. Study the graph in the figure below and answer the
following questions (Steps 2-7) in your notebook.
isos
l.l
I
tr11,
l lt i
!11|
IIi
'a
:.1
I trt
:l:l
fi
!
\
?
?
r&eo
j
I
E
!
I
n
tl
ry
l:,:l
I9C5 tgrs
lffin
,
,,\
I
ls:$
t
I
15q{
Fff*
2.
What was the size of the population at the beginning of the study? ln 1920? What was the difference in the
number of reindeer between 1911 and 1920? What was the average annual increase in the number of
reindeer each year between 1911 and1920?
3.
What was the difference in population size between the years 1920 and 1930? What was the average annual
increase in the number of reindeer in each of the years between 1920 and 1930?
4.
What was the average annual increase in the number of reindeer in each of the years between 1930 and
1
938?
5.
During which of the three periods, 1911-1920, 1920-1930, or 1930-1938 was the increase in the population
ofreindeer greatest?
6.
What was the greatest number of reindeer found on St. Paul Island between
did this occur?
7
.
l9l0
and 1950? ln what year
In 1950, only eight reindeer were still alive. What is the average annual decrease in the number of reindeer
between 1938 and 1950?
Populotion Growth
Discussion
l.
Could emigration or immigration have played a major role in determining the size of the reindeer
population? Explain your answer.
2.
What might account for the tremendous increase in the population of reindeer between 1930 and 1938,
compared with the rate of growth during the first years the reindeer were on the island?
3.
4.
What effect might 2000 reindeer have on the island and its vegetation?
5.
Beginning in 1911, in which time spans did the population double? How many years did it take each
these doublings to occur? What happened to the doubling time between 1911 and 1938?
6.
If some of the eight reindeer that were still alive in 1950 were males and some females, what do you predict
would happen to the population in the next few years? Why?
7.
8.
What evidence is there that the carrying capacity for reindeer on the island was exceeded?
as
Consider all the factors and organism requires to live. What might have happened on the island to cause the
change inpopulation size between 1938 and 1950?
of
What does this study tell you about unchecked population growth? What difference might hunters or
predators have?
Part B: Human Population
Procedure
1.
2.
.-
3.
On the graph paper provided, plot the growth of the human population using the data in the following table.
Use your graph to determine the doubling times for the human population between AD 1 and 1990. How
much time elapsed before the human population of AD I doubled the first time? Is the amount of time
needed for the human population to double increasing or decreasing? What does that indicate about how
fast the human population is growing? Record your answers in your notebook.
Extend your graph to the year 2000. What do you estimate the human population
Human Population Growth Between AD
Date
Human
Date
(AD)
(AD)
Population
(millions)
I
2s0
1000
280
1200
384
1500
1650
427
470
(Black Death)
694
1750
l 100
1850
1900
4.
1920
1930
1940
1950
1960
1980
1985
1990
I
will be in that year?
and 1990
Human
Population
(millions)
I
800
2070
2300
2500
3000
44s0
4850
5300
1600
Using the equations below, estimate the doubling time for the current population based on the rate of
growth from 1980 to 1990. In what year will the present population double?
Rate of growth
(%):
Doubling time
:
(population in 1990 -population in 1980) x 100
population in 1980 x number of years
70 lrate of growth
Populotion Growth
Discussion
1.
What similarities do you see between the graph of the reindeer population and your graph of the human
population?
2.
3.
What are the three or four most important factors required to sustain a population?
4.
5.
6.
7.
8.
9.
In what ways is the Earth as a whole similar to an island such as St. Paul? Does the Earth have a carrying
capacity? Explain your answer.
What might happen to the population of humans if the present growth rate continues?
What methods could be used to reduce the growth rate?
Cite a place in the world where population growth is a problem today. How is it a problem?
Cite a place in the world where population growth is Nor a problem today. Why is it not a problem?
Suggest several problems in the United States that are related to the human population.
What are the most important three or four factors to think about with regard to the world population?