Populations Option 1
Mini-Lab
Rules:
1. Surviving mice of each generation always double in number.
 Ex: if 6 mice survived, add 6 mice to your bowl for a total
of 12 mice
2. There must be a MINIMUM of 10 mice at the beginning of each
generation.
 If you have fewer than 10 mice, bring your population up
to 10.
3. There must be at least 1 coyote at the beginning of each
generation, by immigration if necessary.
4. The maximum amount of mice is 100 (this is NOT carrying
capacity).
 You can’t have more than 100 mice in your ecosystem
5. Each coyote must catch at least 2 mice to survive.
 If you don’t catch 2 mice, you die…poor coyote, nature is
tough.
6. Each coyote must catch at least 5 mice to reproduce. (1offspring
per 5 mice)
 If you catch 10 mice, you will add 2 coyotes to your
population for a total of 3
To Play:
1. Place 10 mice in the field (bowl- must stay flat on the desk)
2. Make 1 pass through the field with the spoon (this is the coyote)
catching as many mice as possible.
3. Add more coyotes and mice according to the rules.
4. Record the starting number of mice and coyotes on the data
table.
5. Repeat the predation, with each coyote being equal to 1 pass
through the field. For example if you have 3 coyotes, then you
make three passes through the filed with each pass representing
a coyote.
Name:________________
Data
Generation
#
1
Mice
(starting
population
number in bowl)
Coyote
(starting
population
number in bowl)
10
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Graph your data on the graph paper provided on the next page.
Graphing Extensions
A. What do you predict would happen to the mice if some coyotes died of
disease or were killed by humans? Explain your answer and on your graph
use a GREEN pencil to show your prediction. Start your prediction after
your last cycle on the graph and continue three more generations.
B. What would happen to the coyotes on your graph if fire killed the prey
population? Explain and show on the graph with RED pencil how the
graph would change. Start after your last cycle and continue three
generations.
C. Would it matter at what point in your simulation such disturbances (like
in A & B) occurred? Explain.
Analysis
1. Give two factors that caused a decrease in the mice population.
2. Give two factors that caused an increase in the mice population.
3. Give three factors that caused a decrease in the coyote population.
4. Give two factors that caused an increase in the coyote population.
5. Predict what would have happened to the mice population if another
food source for the coyotes was introduced?
6. What is carrying capacity?
7.
According to your data, what was the carrying capacity for mice and
for coyotes in your ecosystem?
8. What happens to a population that overshoots its carrying capacity?
9. Did either the mice or coyote population overshoot carrying capacity?
If so, how many generations did it take for the population to rapidly
decline?
Limiting Factors
In the context of populations, a limiting factor is a factor that causes population
growth to decrease.
Density-Dependent Factors
A limiting factor that depends on population size is called a density-dependent limiting
factor. Density-dependent factors operate only when the population density reaches a
certain level. These factors operate most strongly when a population is large and
dense. They do not affect small, scattered populations as greatly.
Density-dependent limiting factors include:
• competition
• predation
• parasitism
• disease
Density-Independent Factors
Density-independent limiting factors affect all populations in similar ways, regardless
of the population size.
Examples of density-independent limiting factors include:
• unusual weather such as a drought
• natural disasters
• seasonal cycles
• certain human activities—such as damming rivers and clear-cutting forests
Moose, wolves cling to Isle Royale
Animals have been studied on the island for about 45 years
By Anita Weier
ISLE ROYALE -- Moose came to this remote island in Lake Superior at least 100
years ago, probably swimming from the mainland to enjoy a tree-filled paradise
without predators.
Then, in about 1949, timber wolves padded across the ice to join them on the 45mile-long, 9-mile-wide island.
In 1958, U.S. Fish and Wildlife Service biologist Durward Allen launched a study to
find out exactly how the two species would interact in an isolated environment.
Would the wolves kill off the moose? Would the wolves survive? Would either species
develop problems from interbreeding?
Rolf Peterson, a professor of wildlife ecology at Michigan Technological University,
has continued the study since 1970, making lengthy visits to the island every year.
Here is a little of what they have learned from what is probably the world's longestrunning predator-and-prey research project.
For some years, there was equilibrium between the species. The moose population
would build to a high level and then crash if there was a very harsh winter. Wolves
would proliferate for about 10 years after a moose peak, as the moose aged and
became vulnerable to attack by wolf packs, Peterson explained.
But in the early 1980s, a dog was among the visitors to the island, though they are
not allowed. The animal was the apparent source of parvovirus, a dangerous new virus
that decimated the wolves, which are still struggling to replenish their numbers: There
were 50 in 1980, but now there are only 19.
A moose die-off occurred in 1996, when two-thirds of the 2,000 moose starved to
death during an extremely bad winter.
Currently there are about 900 moose on the island, Peterson estimated. The moose
will face problems when the balsam fir trees that provide most of their food die off.
"Those old trees crash to the ground after 100 years," Peterson said.
Moose are also being infested by tens of thousands of ticks per animal, which has
caused many to rub off or bite off much of their hair.
The cow moose defend their offspring against wolves by swimming to smaller,
nearby islands to give birth, so the calves are protected from wolves when they are
vulnerable.
If attacked, moose back up to a protected area and use their hooves. Wolves try to
clamp onto a moose's back legs and latch on until the animal topples. Isle Royale
wolves often have broken bones and other injuries from being kicked and bashed
against rocks.
"That's how they get their ribs broken. It takes a lot to unclench their jaws,"
Peterson said of the wolves.
But, on average, just one of every 19 wolf attacks succeeds, usually against the very
old or young moose. The predators have better luck with beaver and other smaller
creatures.
Throughout the years, the researchers have watched for signs of deterioration in
wolves or moose due to inbreeding. No new bloodlines have arrived, so all have
common ancestors and are interrelated to some extent.
"Moose were isolated here 100 years ago. Most of the genes are still here, but they
have a large enough population (to compensate). There are so few wolves that they
have lost genetic variability. The scientific dogma suggests that they are not going to
make it," Peterson said.
Only 12 wolves were on the island in the 1990s, but three older females produced
enough to keep the packs going.
The wolves have also been helped by natural selection along the way, because the
least fit animals die while the strong reproduce.
But a few abnormalities have occurred in wolves in the last two years, Peterson
said.
One had asymmetrical neck vertebrae, though the right and left vertebrae should
be the same. And one had two fused toes on his two front feet. "He was killed by the
pack," Peterson said.
Anita Weier writes for the Capital Times in Madison, Wis. This report was
distributed by The Associated Press.
Use the article above to answer the following questions.
10. How does the wolf population vary when the moose numbers change?
11. How is the decrease in genetic diversity impacting the wolves of Isle
Royale?
12. How did the canine parvovirus ultimately end up effecting the moose
population?
13. Describe how the data from your simulation are similar or different
from the Isle Royal data. If your results from your simulation are very
different explain what could account for this.
14. In the lab investigation you examined only the simple relationship
between changing prey populations and the number of predators.
What other factors affect the number of prey and predators in a
population (be specific)?
15. Review the Isle Royale article and identify as many density dependent
and density independent limiting factors as you can
Density Dependent
Density Independent