Download The Lesson of the Kaibab

Chapter 8
Population
Density
dispersion
Growth rate
Reproductive potential
Exponential growth
Carrying capacity
niche
competition
predation
parasitism
mutualism
commensalism
symbiosis
Chapter 8 ~ HOW POPULATIONS GROW
I.
Characteristics of ____________
A. 3 important characteristics:
1. _____________ distribution
a) Area _______________ by a _______________
2. Density
a) Number of _____________ per unit area
3. Growth ___________
II.
Population Growth
A. 3 factors affect population ________:
1. Number of ___________
2. Number of ____________
3. Number of individuals that _________ or __________ a population
a) ______________ and emigration
B. Will ____________ if more individuals are ____________ than die
C. Will ______________ if more individuals ____________ than are born
D. Will remain the ___________ if _________ numbers die and are born
III.
Exponential Growth
A. Under ideal conditions with __________ resources, a population will grow exponentially
B. _______________ with each generation
C. Ideal conditions __________ occurs in nature, so exponential growth ______________ normally
occur in nature
IV.
Logistic Growth
A. ___________ population
1. Growth starts _____________
2. Growth becomes exponential
3. As resources become __________ growth ________ or stops
4. It will hover around the same number
a) The carrying capacity
LIMITS TO GROWTH
I.
Limiting Factors
A. A factor that causes population growth to _________________
1. _________________
2. Predation
3. Parasitism and _________
4. _____________ and other climate extremes
5. _____________ disturbances
B.
II.
Can effect the long term _________ of a species
Density _______________ Factors
A. A limiting factor that depends on population ____________
B.
III.
Become limiting only when the number of organisms reaches a certain _______
1. They do not effect _________ populations as strongly
C. Include:
1. ________________
2. Predation
3. ____________ and disease
Competition
A. Organisms compete for:
1. _________
2. Water
3. ___________
4. Sunlight
5. Other essential _________
B. Competing organisms can be from the __________ species or _____________ species
IV.
Predation
A. Large prey population
B. Predator population _____________ because there is more to eat
C. More prey will be eaten
D. Prey population decreases
E. Less prey to eat, so ______________ population will decrease
V.
Parasitism and Disease
A.
The ____________ the population, the more likely it is to be _____________ with parasites
due to close living quarters
VI. Mutualism
A. When both organisms involved in a reaction benefit…
VI.
Density-Independent Factors
A. Affects all populations regardless of ____________
1. ________________
2. _____________ disasters
3. Seasonal __________
4. Certain human activities:
a) Damming rivers
b) Clear cutting _________
B. A population ___________ follows, may or may not recover
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 livestock grazing permits. By
1923, the deer were reported to be on the verge of starvation and the range conditions were described as
"deplorable."
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
1. Graph the deer population data. Place time on the X axis and "number of deer" on the
Y axis. Make a LINE GRAPH!
DATA TABLE
Year
Deer
Population
1905
4,000
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
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 did the population of deer decline in 1925?
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. Based on these lessons, suggest what YOU would have done in the following years to manage deer
herds.
1915:
1923:
Ch. 8 ~ Study Guide
1. Name 3 factors that affect population growth
__________________________________
__________________________________
__________________________________
2. Explain the concept of exponential growth: _______________________________________
_________________________________________________________________________
3. Draw a graph depicting exponential growth:
4. Explain the concept of logistical growth: __________________________________________
__________________________________________________________________________
5. Draw a graph depicting logistical growth:
6. List 5 limiting factors to population growth:
__________________________________________
__________________________________________
__________________________________________
__________________________________________
__________________________________________
7. Define a Density Dependent Factor: _____________________________________________
_________________________________________________________________________
8. Does it affect a large or small population? ________________________________________
9. List 3 Density Dependent Factors:
__________________________________________
__________________________________________
__________________________________________
10. Define a Density Independent Factor: ___________________________________________
_________________________________________________________________________
11. What kind of population does it affect? __________________________________________
12. List 4 Density Independent Factors:
_________________________________________
_________________________________________
_________________________________________
_________________________________________
13. What may happen to a population as a result of experiencing one or more of the factors
From question 12? _________________________________________________________
_________________________________________________________________________