Limiting Factors and Carrying Capacity
DO NOW WEDNESDAY
•Explain what limiting factors are. Give some examples.
•What is carrying capacity?
Objective: How a Predator-Prey Population Changes Over Time
Key Words: Natural Resources, Limiting Factors, Carrying Capacity
Scenario
•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 service 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.
Objective: How a Predator-Prey Population Changes Over Time
Key Words: Natural Resources, Limiting Factors, Carrying Capacity
Results of the program
• The results of this program are shown in the following table.
Data Table
Trials (years)
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
Number of Deer
2,000
2,300
2,500
2,360
2,224
2,094
1,968
1,916
1,952
1,972
10
12
16
22
28
24
21
18
19
19
Number of Wolves
1. Graph the deer and wolf populations on the graph below in a graph line. Use one color to
show deer population and another color to show wolf population.
Objective: How a Predator-Prey Population Changes Over Time
Key Words: Natural Resources, Limiting Factors, Carrying Capacity
Deer and Wolf Populations from 1971 to 1980
Conclusions
2. How did the deer and wolf populations change over time?
• Deer and wolf populations first increased, then decreased, and then became stable.
Objective: How a Predator-Prey Population Changes Over Time
Key Words: Natural Resources, Limiting Factors, Carrying Capacity
Deer and Wolf Populations from 1971 to 1980
d. Discussion
3. Once the wolves were introduced, what is the carrying capacity for deer and wolves in the
ecosystem?
• Deer’s carrying capacity is 1960. Wolf’s carrying capacity is 19.
4. What do you think would have happened to the deer on the island if the wolves had NOT
been introduced?
• Initially, deer’s population would increase because there would be no predators .
Then, deer’s population would decrease, because deer would have used up all of the
resources and then starve to death.
Objective: How a Predator-Prey Population Changes Over Time
Key Words: Natural Resources, Limiting Factors, Carrying Capacity
Deer and Wolf Populations from 1971 to 1980
d. Discussion
5. What limiting factors affect deer population?
• Water, food, shelter, predators, diseases, and climate.
6. What limiting factors affect wolf population?
• Water, food, shelter, diseases, and climate.
Objective: How a Predator-Prey Population Changes Over Time
Key Words: Natural Resources, Limiting Factors, Carrying Capacity
Deer and Wolf Populations from 1971 to 1980
Less wolves
Deer and wolf
Less deer populations More deer
depend on
each other.
More wolves
d. Discussion
7. How would you describe the relationship between the deer and wolf population?
• Deer and wolf populations depend on each other.
• Both show the same pattern: increase and decrease, then become stable.
Objective: How a Predator-Prey Population Changes Over Time
Key Words: Natural Resources, Limiting Factors, Carrying Capacity
Deer and Wolf Populations from 1971 to 1980
d. Discussion
8. Would you agree or disagree with the following statement. “Predators and prey exist in a
balance.” Explain.
• Agree, because…
• Or disagree, because…
Objective: How a Predator-Prey Population Changes Over Time
Key Words: Natural Resources, Limiting Factors, Carrying Capacity
Deer and Wolf Populations from 1971 to 1980
d. Discussion
9. What are the advantages of having a population of predators and prey in an ecosystem?
• It increases biodiversity and makes the ecosystem more stable.
• Predators keep the deer population from becoming too large and prevent mass starvation.
• Predators increase the deer health, as predators often eliminate the weaker members of the
herd.
Objective: How a Predator-Prey Population Changes Over Time
Key Words: Natural Resources, Limiting Factors, Carrying Capacity
10. In certain areas of the United States, the populations of wolves and other predators have
decreased. As a result, deer populations in these areas have increased.
Describe one way that an increase in the deer population can be harmful to humans.
•They transmit diseases to humans, i.e. Lyme disease.
•They cause automobile accidents.
•They eat crops.