Name:________________ Date:___________
POPULATION CHANGES
INTRODUCTION:
Since relying on natural populations requires a lot of time, in this activity we will rely on population data collected by other teams of researchers. Graph one set of population data and then use the graphs to answer the accompanying questions.
Analyze the other two sets of data and graphs. (*Note: We are only requiring you to graph the first set of data, if you want more practice graphing, you SHOULD use the other two sets to practice graphing techniques)
PART A: Permiscus sp. (mice in the Grand Canyon)
Scientists in the Grand Canyon were studying how the water from the Colorado
River flow affected populations in the area. The population statistics were gathered using live traps. Mice were caught, counted and released from 100 traps per month. As is often the case in nature, the actual population number is not known. Even in this real situation, we have to assume that the number of mice caught was in proportion to the actual population density.
MONTH OF
TRAPPING
NUMBER OF MICE
CAUGHT
Jan
Feb
Mar
Apr
May
20
22
30
37
41
Jun
Jul
Aug
42
31
25
Sep 24
Oct
Nov
Dec
20
22
18
Part A: Mice
1. Is this an open or closed population?
2. During which months was natality higher than mortality?
3. During which months was mortality higher than natality?

4. Why do you think natality and mortality are higher at certain times of year?
Explain.
5. Based on the graph, what can you hypothesize about factor(s) that influence the mouse population in this area?
6. What are some experimental issues with this sampling technique?
9
10
11
5
6
7
8
1
2
3
4
PART B: Drosophilia melanogaster (a laboratory population)
In this experiment, scientists grew cultures of D. melanogaster (the common fruit fly) in jars. Counts were taken every day for 3 weeks. Flies were anesthetized, counted, and returned to the closed container.
DAY OF
EXPERIMENT
NUMBER OF FLIES
4 (2 male, 2 female)
4
4
8
18
40
8
155
322
612
622
DAY OF
EXPERIMENT
12
13
14
15
16
17
18
19
20
21
NUMBER OF FLIES
630
422
356
255
120
77
36
15
5
0

Part B: Fruit Flies
1. Is this an open or closed population?
2. Describe the type of growth curve shown from Days 1-10. Why does this type of growth occur during this time period?
3. What do you think is responsible for the changes in the population from Days 11-
21?
4. Describe some limiting factors for the fruit fly population in this jar.

PART C: Homo Sapiens
The following data, obtained, from census records, represents the human population of the United States from 1790-2000.
YEAR POPULATION (in millions of people)
1800
1820
1840
1860
1880
1900
1920
1940
1960
1980
2000
5
10
18
31
50
77
106
132
179
226
281
Part C
1. Does the human graph more closely resemble the mouse or the fruit fly graph?
2. Is the human population on Earth (the whole planet) an open or closed population?

3. If the growth rate continues as it has over the last 100 years, what do you predict will happen to the human population? What do you predict will happen to the environment and the other species on Earth?
Case Study: (from POGIL Activities for High School Biology)
Invasive species are species that are introduced into an environment but are not naturally found in the environment. One example of an invasive species is the
American gray squirrel, introduced into Britain at the end of the 18 th century. Until
1876 the only native squirrel in Britain was the European red squirrel, which was found in deciduous and coniferous forests. By 1940 the gray squirrel had displaced the red squirrel across most of the British Isles, and by 1984 the red squirrel was only found in isolated coniferous woodland areas. After its initial introduction, the gray squirrel population increases rapidly; however, in recent years population sizes within specific environment have become stable.
1.
Explain why the newly-introduced gray squirrel initially showed rapid population growth and why the native red squirrel showed a population decline. Use ecological terms from the previous models in your answer.
2.
Why has the population size of the gray squirrel become stable in recent years?