deer population dynamics
What is happening to this
population?
20
number of deer
18
16
14
12
10
8
6
4
2
0
0
2
Why doesn’t the
population ever go
above 18?
4
6
8
Year
10
12
14
Carrying Capacity
The number of organisms of one
species that an environment can support
indefinitely.
18 is the Carrying Capacity for our population.
deer population dynamics
20
number of deer
18
16
14
Why does population
increase?
12
10
8
6
4
2
0
0
2
4
6
8
Year
10
12
14
Population Growth
• An increase in the number of
individuals in a population
Unlimited resources and reproduction lead
to population growth (G)
Growth = Births – Deaths
(G = B – D)
Population Growth
When births exceed deaths you see
population growth.
600
500
J-Shaped Curve
400
300
Series1
200
100
0
0
2
4
6
8
10
12
Exponential Growth
• Exponential growth means that as a population
gets larger, it also grows at a faster rate.
600
500
J-Shaped Curve
400
300
Series1
200
100
0
0
2
4
6
8
10
12
Reproduction Patterns:
Rapid life-history patterns
• Rapid life-history patterns are common among
organisms from changeable or unpredictable
environments.
20
MINUTES!
Reproduction Patterns:
Slow life-history patterns
• Large species that live in more stable
environments usually have slow lifehistory patterns.
• Reproduce and mature
slowly, and are longlived.
22
MONTHS!
• Maintain population
sizes at or near carrying
capacity.
Growth Limitations
•
•
•
•
Resources
Disease
Organism interaction
Habitat
Size/Crowding
• Weather
When a population
overshoots the
carrying capacity,
then limiting
factors may come
into effect.
Deaths begin to exceed births and the
population falls below carrying capacity
population growth over 20 years
600
500
population
S - Curve
400
300
200
100
0
0
2
4
6
8
10
year
12
14
16
18
20
Two types of limiting factors:
Density-dependent
and
Density-independent
Population density describes the number of
individuals in a given area.
Population Density
• Let’s say our classroom is 600 sq. ft.
In 3rd hour and fifth hour, there are 25
students in the class.
The population density for 3rd and 5fth hour is
25 students/600 ft² or .04 students/ft².
In 6th hour, there are only 19 students in the
class. Is the population density higher or
lower?
Density - Dependent
• Density-dependent factors include disease,
competition, predators, parasites, and food.
• Disease, for example, can spread more
quickly in a population with members that
live close together.
Its flu season, and lots of sick students are coming to
school. They are coughing, sneezing, and touching
everything. Ten percent of Ms. Sonleitner’s students
have the flu, but are so dedicated they come to class
anyway. If Ms. Sonleitner wipes down every table
before every class, which class will be most affected
by the flu?
3rd and 5th hours, because they have the greatest
population density. A larger number of students
will be infected and have opportunity to infect a
larger number of healthy students.
Density - Independent
• Density-independent factors can affect all
populations, regardless of their density.
• Most density-independent factors are
abiotic factors, such as temperature, storms,
floods, drought, and major habitat
disruption
Six new students were added to sixth hour.
The population densities of all the classes is
now the same.
The school is sponsoring an event that allows
students to miss 3rd, 5th, and 6th hours. Which
classes will be most effected?
• All equally effected! The event will disrupt
class regardless of size – everyone will have
the opportunity to go.
Organism Interactions
• Population sizes are controlled by various
interactions among organisms that share a
community.
• Predation and competition are two
interactions that control populations.
Predation
Populations of predators and their prey
experience cycles or changes in their
numbers over periods of time.
Lynx and Hare pelts sold to the Hudson’s Bay Company
Competition
•
Is Density - Dependent
• When only a few individuals compete for
resources, no problem arises.
• When a population increases to the point at
which demand for resources exceeds the
supply, the population size decreases.
Crowding
• As populations increase in size in
environments that cannot support increased
numbers, individual animals can exhibit a
variety of stress symptoms.
• These include aggression, decrease in
parental care, decreased fertility, and
decreased resistance to disease.
• They become limiting factors for growth and
keep populations below carrying capacity.
Population of New Orleans, La 1970-2006
650000
population
550000
450000
350000
250000
150000
50000
-500001968
1973
1978
1983
1988
1993
1998
2003
2008
year
1. What are the independent and dependent variables?
2. What is the population trend?
3. Why did this happen? Is this density-dependent or
independent?
Global population 1900 - 2046
Population in Billions
10
9
8
7
6
recorded population
5
projected population
4
3
2
1
0
1850
1900
1950
2000
2050
2100
Years
4. What type of growth is this?
5. When does growth increase? What might have happened
to cause this?