Ecology Graphing Packet
Name_________
Reading and creating population graphs.
Deer: Predation or Starvation
Introduction: In 1970 the deer population of an island forest reserve about 518 square kilometers in size
was about 2000 animals. Although the island had excellent vegetation for feeding, the food supply
obviously had limits. Thus the forest management personnel feared that overgrazing might lead to mass
starvation. Since the area was too remote for hunters, the wildlife seervice decided to bring in natural
predators to control the deer population. It was hoped that natural predation would keep the deer population
from becoming too large and also increase the deer quality (or health), as predators often eliminate the
weaker members of the herd. In 1971, ten wolves were flown into the island.
The results of this program are shown in the following table. The Population Change is the number of deer
born minus the number of deer that died during that year. Fill out the last column for each year (the first has
been calculated for you).
Year
Wolf
Population
Deer
Population
Deer Offspring
Predation
Starvation
Deer Population
Change
1971
10
2,000
800
400
100
+300
1972
12
2,300
920
480
240
1973
16
2,500
1,000
640
500
1974
22
2.360
944
880
180
1975
28
2,224
996
1,120
26
1976
24
2,094
836
960
2
1977
21
1,968
788
840
0
1978
18
1,916
766
720
0
1979
19
1,952
780
760
0
1980
19
1,972
790
760
0
1. Graph the deer and wolf populations on the graph below. Use one color to show deer populations and
another color to show wolf populations.
Analysis
1. Describe what happened to the deer and wolf populations between 1971 and 1980.
2. What do you think would have happened to the deer on the island had wolves NOT been introduced?
3. Most biology textbooks describe that predators and prey exist in a balance. This "balance of nature"
hypothesis has been criticized by some scientists because it suggests a relationship between predators and
prey that is good and necessary. Opponents of this hypothesis propose the following questions:
Why is death by predators more natural or "right" then death by starvation?
How does one determine when an ecosystem is in "balance"?
Do predators really kill only the old and sick prey? What evidence is there for this statement?
What is your opinion of the balance of nature hypothesis? Would the deer on the island be better off, worse
off, or about the same without the wolves. Defend your position.
The Lesson of the Kaibab
Introduction: The environment may be altered by forces within the biotic community, as well as by
relationships between organisms and the physical environment. The carrying capacity of an ecosystem is
the maximum number of organisms that an area can support on a sustained basis. The density of a
population may produce such profound changes in the environment that the environment becomes
unsuitable for the survival of that species. For instance, overgrazing of land may make the land unable to
support the grazing of animals that lived there.
Objectives:



Graph data on the Kaibab deer population of Arizona from 1905 to 1939
Determine factors responsible for the changing populations
Determine the carrying capacity of the Kaibab Plateau
Background
Before 1905, the deer on the Kaibab Plateau were estimated to number about 4000. The average carrying
capacity of the range was then estimated to be about 30,000 deer. On November 28th, 1906, President
Theodore Roosevelt created the Grand Canyon National Game Preserve to protect the "finest deer herd in
America."
Unfortunately, by this time the Kaibab forest area had already been overgrazed by sheep, cattle, and horses.
Most of the tall grasses had been eliminated. The first step to protect the deer was to ban all hunting. In
addition, in 1907, The Forest Service tried to exterminate the predators of the deer. Between 1907 and
1939, 816 mountain lions, 20 wolves, 7388 coyotes and more than 500 bobcats were killed.
Signs that the deer population was out of control began to appear as early as 1920 - the range was
beginning to deteriorate rapidly. The Forest Service reduced the number of
DATA TABLE
livestock grazing permits. By 1923, the deer were reported to be on the
Year
Deer Population
verge of starvation and the range conditions were described as
"deplorable."
1905
4,000
The Kaibab Deer Investigating Committee recommended that all livestock
not owned by local residents be removed immediately from the range and
that the number of deer be cut in half as quickly as possible. Hunting was
reopened, and during the fall of 1924, 675 deer were killed by hunters.
However, these deer represented only one-tenth the number of deer that had
been born that spring. Over the next two winters, it is estimated that 60,000
deer starved to death.
Today, the Arizona Game Commission carefully manages the Kaibab area
with regulations geared to specific local needs. Hunting permits are issued
to keep the deer in balance with their range. Predators are protected to help
keep herds in balance with food supplies. Tragic winter losses can be
checked by keeping the number of deer near the carrying capacity of the
range.
DATA
1910
9,000
1915
25,000
1920
65,000
1924
100,000
1925
60,000
1926
40,000
1927
37,000
1928
35,000
1929
30,000
1930
25,000
1931
20,000
1935
18,000
1939
10,000
1. Graph the deer population data. Place time on the X axis and "number of deer" on the Y axis
Analysis
1. During 1906 and 1907, what two methods did the Forest Service use to protect the Kaibab deer?
2. Were these methods successful? Use the data from your graph to support your answer.
3. Why do you suppose the population of deer declined in 1925, although the eliminated of predators
occurred?
4. Why do you think the deer population size in 1900 was 4,000 when it is estimated that the plateau has a
carrying capacity of 30,000?
5. Why did the deer population decline after 1924?
6. Based on these lessons, suggest what YOU would have done in the following years to manage deer
herds.
1915:
1923:
7. It is a criticism of many population ecologists that the pattern of population increase and subsequent
crash of the deer population would have occurred even if the bounty had not been placed on the predators.
Do you agree or disagree with this statement. Explain your reasoning.
8. What future management plans would you suggest for the Kaibab deer herd?
Human Population Growth
Objectives:
You will create a graph of human population growth and use it to predict future growth.
You will identify factors that affect population growth.
Statisics on Human Population
Year A.D.
Number of People (in billions)
1650
.50
1750
.70
1850
1.0
1925
2.0
1956
2.5
1966
3.3
1970
3.6
1974
3.9
1976
4.0
1980
4.4
1991
5.5
2000
6.0
2004
6.4
In 2011, there are about 6.9 billion humans on the planet.
Instructions for creating your graph.
Place time on the horizontal access. Values should range from 1650 to 2020.
Place number of people on the vertical access. Values should range from 0 to 20 billion.
Make sure that your graph is a full page in size and you have the correct labels for the X and Y access and a
title for your graph.
Analysis
1. It took 1649 years fro the world population to double, going from .25 billion people to .50 billion people.
How long did it take for the population to double once again?
2. How long did it take for the population to double a second time? ___________ A third time?
________________
3. Based on your graph, in what year will the population reach 8 billion? _____________
4. Based on your graph, how many years will it take for the population of 2004 to double?
______________
The Earth's Carrying Capacity
Prior to 1950, the death rate was high, which kept the numbers of humans from increasing rapidly. In the
19th Century, the agricultural revolution increased food production. The industrial revolution improved
methods of transporting food and other good. In the 20th Century, advances in medicine, sanitation and
nutrition have decreased the death rates further. These factors combined to produce the rapid growth of the
human population in the 20th century.
As with any population, humans are also limited by factors such as space, amount of food and disease. The
carrying capacity is the number of individuals that a stable environment can support. Authorities disagree
on on the maximum number of people that the earth can support, though the numbers generally range for 8
to 10 billion. As the population approaches its limit, starvation will increase. Some countries have a much
higher growth rate than others. Growth rate is the number of people born minus the number of people that
die. Compare the growth rates of the following countries
Most countries are trying to reduce their growth rate. Zero population growth means that as many people
are being born as there are dying - to achieve zero population growth, each couple would need to have no
more than two children (to replace the parents). Even if this number is achieved, the population will
continue to grow because the parents will still live on for decades, as their children have children and their
children have children..and so forth. The United States reached zero population growth in the 1980's, and
yet the overall population of the US still increases.
Analysis
1. What factors contributed to the world's overall population growth in the last 150 years.
2. Why does a population not level off during the same year it reaches zero population growth?
3. If the carrying capacity of the earth was 9 billion people, when would this number be reached (according
to your graph)?
4. What will happen when the human population exceeds the earth's carrying capacity?
INTERPRETING ECOLOGICAL DATA
Graph 1: Rabbits Over Time
a. The graph shows a __________ growth
curve.
b. The carrying capacity for rabbits is
______
c. During which month were the rabbits in
exponential growth?
Graph 2: Average Toe Length
a. In 1800, about how many people surveyed
had a 3 cm toe? _______
How many in 2000? _______
b. The data shows the ____________
selection has occurred?
c. In 2000, what is the average toe length?
______ What is the average toe length in
1800 _______
Graph 3: Mexico and US
a. In Mexico, what percentage of the
population is between 0-4 years of age?
_______ In the US? ______
b. Which population is growing the fastest?
________
c. Which age group has the smallest number
in both countries? _____
Chart 4: Trapping Geese
In order to estimate the population of geese in Northern Wisconsin,
ecologists marked 10 geese and then released them back into the
population. Over a 6 year period, geese were trapped and their
numbers recorded.
a. Use the formula to calculate the estimated number of geese in the
area studied? _____________
b. This technique is called ____________ & ______________
c. Supposing more of the geese found in the trap had the mark,
would the estimated number of geese in the area be greater or lesser?
_____
Chart 5: Mushroom Plots
Another ecologist uses a different method to estimate the number of
mushrooms in a forest. She plots a 10x10 area and randomly chooses
5 spots, where she counts the number of mushrooms in the plots and
records them on the grid.
a.Calculate the number of mushrooms in the forest based on the grid
data: _________________
b. Thie technique is called _______________
Year
Geese
Trapped
Number with Mark
1980
10
1
1981
15
1
1982
12
1
1983
8
0
1984
5
2
1985
10
1
Chart 6: Snakes & Mice
Year
Snakes
Mice born
Mice
died
The data shows populations of snake and mice found in an experimental
field.
1960
2
1000
200
1970
10
800
300
1980
30
400
500
1990
15
600
550
2000
14
620
600
2001
15
640
580
a. During which year was the mouse population at zero population
growth? ______
b. What is the carrying capacity for snakes ? ______
c. What is the carrying capacity for mice? _____
d. What is the rate of growth (r) for mice during 1970? _____ During
1980? ______
Random Sampling
Scientists cannot possibly count every organism in a population. One way to estimate the size of a population is to collect
data by taking random samples. In this activity, you will look at how data obtained from random sampling compare with
data obtained by an actual count.
Procedure:
1. Tear a sheet of paper into 20 slips, each approximately 4cm x 4 cm.
2. Number 10 of the slips from 1 to 10 and put them in a small container
3. Label the remaining 10 slips from A through J and put them in a second container.
The grid shown below represents a meadow measuring 10 m on each side. Each grid segment is 1m x 1m. Each black circle
represents one sunflower plant.
4. Randomly remove one slip from each container. Write down the number-letter combination and find the grid segment that
matches the combination. Count the number of sunflower plants in that grid segment. Record this number on the data table.
Return each slip to its appropriate container.
5. Repeat step 5 until you have data for 10 different grid segments (and the table is filled out). These 10 grid segments
Random Sampling Data
Grid Segment
(number-letter)
Number of
Sunflowers
Actual Data
Total number of Sunflowers ______
(count by hand)
Average number of Sunflowers
(divide total by 10) Per grid _____
Total Number of
Sunflowers
Average per grid
(divide total by 10)
Total number ofplants in meadow
(multiply average by 100)
represent a sample. Gathering data from a randomly selected sample of a larger area is called sampling.
6. Find the total number of sunflower plants for the 10 segment sample. This is an estimation based on a formula. Add all the
grid segment sunflowers together and divide by ten to get an AVERAGE number of sunflower plants per grid segment.
Record this number in the table. Multiple the average number of sunflower plants by 100 (this is the total number of grid
segments) to find the total number of plants in the meadow based on your sample. Record this number in your data table
7. Now count all the sunflower plants actually shown in the meadow. Record this number in the data table. Divide this
figure by 100 to calculate the average number of sunflower plants per each grid.
Analysis:
1. Compare the total number you got for sunflowers from the SAMPLING to the ACTUAL count. How close are they?
2. Why was the paper-slip method used to select the grid segments?
3. Why do biologists use Sampling? Why can’t they just go into the forest and count all the sunflower plants?
4. Population Sampling is usually more effective when the population has an even dispersion pattern. Clumped dispersion patterns are the least
effective. Explain why this would be the case.
5. Describe how you would use Sampling to determine the population of dandelions in your yard.
6. In a forest that measures 5 miles by 5 miles, a sample was taken to count the number of silver maple trees in the forest. The number of trees
counted in the grid is shown below. The grids where the survey was taken were chosen randomly. Determine how many silver maple trees are in this
forest using the random sampling technique. Show your work!
7
3
5
11
9
Examining the Stages in Ecological Succession
Succession, a series of environmental changes, occurs in all ecosystems. The stages that any ecosystem
passes through are predictable. In this activity, you will place the stages of succession of two ecosystems
into sequence. You will also describe changes in an ecosystem and make predictions about changes that
will take place from one stage of succession to another.
The evolution of a body of water from a lake to a marsh can last for thousands of years. The process cannot
be observed directly. Instead, a method can be used to find the links of stages and then to put them together
to develop a complete story.
The water level of Lake Michigan was once 18 meters higher than it is today. As the water level fell, land
was exposed. Many small lakes or ponds were left behind where there were depressions in the land. Below
are illustrations and descriptions of four ponds as they exist today. Use the illustrations and descriptions to
answer the questions about the ponds.
Pond A: Cattails, bulrishes, and water lilies grow in the pond. These plants have their roots in the bottom of
the pond, but they can reach above the surface of the water. This pond is an ideal habitat for the animals
that must climb to the surface for oxygen. Aquatic insect larvae are abundant. They serve as food for larger
insects, which in turn are food for crafish, frogs, salamanders, and turtles.
Pond B: Plankton growth is rich enough to support animals that entered when the pond was connected to
the lake. Fish make nests on the sandy bottom. Mussels crawl over the bottom.
Pond C: Decayed bodies of plants and animals form a layer of humus over the bottom of the pond. Chara, a
branching green algae, covers the humus. Fish that build nests on the bare bottom have been replaced by
those that lay their eggs on the Chara.
Pond D: The pond is so filled with vegetation that there are no longer any large areas of open water.
Instead, the pond is filled with grasses. The water dries up during the summer months.
Questions
1. Write the letters of the ponds in order from the youngest, to the oldest. _____________________
2. Black bass and bluegill make their nests on sandy bottoms. In which pond would you find them?
______________________
3. What will happen to the black bass and blue gill as the floor of the ponds fills with organic debris?
____________________________________
4. Golden shiner and mud minnows lay their eggs on Chara. In which pond would you find them?
_____________________
5. Some amphibians and crayfish can withstand periods of dryness by burying themselves in mud. In which
pond(s) would they survive? _________
6. Dragonfly nymphs spend their early stages clinging to submerged plants. Then, they climb to the surface,
shed their skins and fly away as dragonflies. Which pond is best suited for
dragonflies?____________________________
7. In which pond will gill breathing snails be replaced by lung breathing snails that climb to the surface to
breathe? ________________
8. Some mussels require a sandy bottom in order to maintain an upright position. In which pond will they
die out. ______________________
The climax community in the area of Michigan is a beech-maple forest. After the ponds are filled in,
the area will undergo another series of stages of succession. This is illustrated below. Briefly explain
what is happening in the diagram.
1. _______________________________________________________________________________
2. _______________________________________________________________________________
3. _______________________________________________________________________________
4. _______________________________________________________________________________
5. _______________________________________________________________________________
Are zebra mussels really invading?
In the mid-1980s a new species found its way to North America. The zebra mussel (Dreissena
polymorpha), a small, clamlike mollusk that grows to about 25 cm as an adult, was introduced into the
waters of the Great Lakes, probably carried in the bilge of a Russian freighter. The zebra mussel can
reproduce in less than a year, and a single female can release 1 million eggs each year. In the absence of
their natural pathogens, parasites, and predators, the zebra mussel populations in the Great Lakes has grown
enormously and are now invading eight major river systems, including the St. Lawrence, Hudson,
Mississippi, Ohio, Illinois, Tennessee, Susquehanna, and Arkansas rivers. The mussels are spread from one
body of water to another by natural flow, carried on the feathers or feet of migrating waterfowl, or by
human transport in bait buckets or on trailered boats. Most of the freshwater systems in North America are
now threatened by invasion of the zebra mussel.
The zebra mussels grow in massive colonies, where nearly a half million individuals may grow on each
square meter of substrate. These colonies encrust the hulls and rudders of ships, the hinges of lock gates,
and block the drains and intake ducts used by industries and power stations. In 1990, for example, Detroit
Edison spent over $500,000 to remove zebra mussels from the intake pipes of its power plants.
The zebra mussels also have severe negative effects on the local ecosystem. As filter-feeders, they take in
water and filter out algae as food, excreting their waste as sediment. A single individual can filter 1 liter of
water each day, and a colony covering 1 square meter of substrate can filter 180 million liters of water per
year. Enormous colonies of zebra mussels can reduce the algal populations of lakes and rivers, thus
removing a significant portion of the base of the food chain and resulting in a decline in the fish
populations. Thus, these mussels are a threat to the local biodiversity.
The tremendous filtering capacity of these organisms may have some positive consequences. Zebra mussels
have been a major factor in cleaning Lake Erie after a century of pollution from fertilizers and sewage.
After the first 10 years of zebra mussel existence in Lake Erie, light penetration in the water has increased
from only a few centimeters to nearly 10 meters. If these organisms could be controlled, they may become
a useful tool in the treatment of sewage and pollution.
(Adapted from: Bush, Mark B. 1997. Ecology of a Changing Planet. Prentice Hall, Upper Saddle River,
N.J.)
Name __________________________________
Questions
1. Which of the following best summarizes the author's main point?
a. Zebra mussels are harmful to the great lakes
b. Zebra mussels are harmful to all lakes
c. The importation of zebra mussels should be regulated
d. Many lakes and river systems are polluted
2. Zebra mussels can move from one lake to another by which method?
a. on the feet of birds
b. carried by the wind
c. moving overland for short periods
d. swimming up canal systems
3. Massive colonies of zebra mussels cause problems because:
a. they destroy the engines of boats
b. they block the flow of water through ducts
c. they produce waste that pollutes the water
d. they eat large amounts of fish
4. Which of the following is a consequence of the zebra mussel population in the great lakes
a. cleaner water
b. decline in algae populations
c. decline in fish populations
d. all of these
5. Why are zebra mussels a problem in the Great Lakes but not in the lake systems where they came from?
a. the other lakes are too cold for them to reproduce in large amounts
b. they have natural predators in the other lakes
c. they cannot leave these lakes
d. they cannot grow into colonies
6. How might zebra mussels be used to improve lake systems?
a. they can be grown as food for humans
b. they can be used to strengthen dams and levies
c. they clean the water of pollutants
d. they remove algae from the water
7. What do zebra mussels eat?
a. algae
b. fish
c. insects
d. water plants
Describe the population trends for the 5 graphs above.
F= population
1.
2.
3.
4.
5.
t=time