POPULATION SIZE
INTRODUCTION
A herd of reindeer moves slowly across the frozen tundra. Arctic fox bound
after mice at the margins of the herd. Willow ptarmigan stand stock still,
camouflaged by the sparse lichens and moss. Individuals of the same species
that interbreed with one another, like the reindeer or arctic fox, make up a
population. In this activity you will examine how populations fluctuate based
on four factors - mortality, natality, immigration, and emigration.
Part A
Reindeer Population
In 1911, 25 reindeer - 4 males and 21 females - were introduced onto St. Paul
Island, one of the Pribolof Islands in the Bering Sea near Alaska. The island
is approximately 41 square miles in size, and is more than 200 miles from the
mainland. There were no predators of the deer, and no hunting of the deer
was allowed. Study the graph below and answer the questions that follow.
Questions
1. – 4. What was the population in 1911? _______ in 1920? _______
What was the population difference between 1911 and 1920? _______
What was the average annual increase between 1911 and 1920? _______
5. – 6. What was the population difference between 1920 and 1930? ________
What was the average annual increase between 1920 and 1930? ________
7. – 8. What was the population difference between 1930 and 1938? ________
What was the average annual increase between 1930 and 1938? _______
9. During which of the 3 periods - 1911-1920, 1920-1930, or 1930-1938 - was the
annual increase in population greatest? ________________________
10. – 11. What was the greatest population found on St. Paul Island between
1911 and 1950? ________________
In what year? ___________
12. In 1950, only 8 reindeer were still alive. What was the average annual
decrease between 1938 and 1950? ________________
Analysis
13. Could immigration or emigration have played a major role in the size of the
population? ________________
Explain. _________________________________
_______________________________________________________________________
14. What might account for the tremendous increase in population between 1930
and 1938? _____________________________________________________________
15. What effect might 2000 deer have on the island and its vegetation?
_______________________________________________________________________
16. What might account for the tremendous decrease in population between 1938
and 1950? ______________________________________________________________
Part B
Human Population
Use the table below to graph the growth of human population. DO NOT
USE BREAKS ON YOUR “DATE IN A.D.” AXIS!!!
Date in A.D.
1
1000
1200
1500
1650
1750
1850
1900
Population (millions)
250
280
384
427
470
Black Death
694
1100
1600
Date in A.D.
1920
1930
1940
1950
1960
1980
1985
1990
2005
Population (millions)
1800
2070
2300
2500
3000
4450
4850
5300
6450
(6,446,131,400)
Title: _________________________________________________________________
Questions
17. Use the graph to give a good estimate for the following:
When did the AD 1 population double for the first time? ________ When did
it double a second time? __________
a third? __________ Is the doubling
time increasing or decreasing? ____________________
18. Use the formulas below to predict the next population doubling.
rate of growth (%) = (population in 1990 - population in 1980) x 100
population in 1980 x 10 years
doubling time
= 70 / rate of growth
Your calculations
Analysis
19. What similarities do you see between the reindeer and human graphs?
_____________________________________________________________________
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20. In what ways is the Earth similar to St. Paul Island?
_____________________________________________________________________
_____________________________________________________________________
21. What might happen to the human population if growth continues?
_____________________________________________________________________
_____________________________________________________________________
22. If necessary, what humane methods might be used to control growth rate?
_____________________________________________________________________
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