# Population Dynamics by yurtgc548

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```									Population Dynamics
What is a population?

• A population is defined as being “all
the organisms of the same type living
in a certain area.”
Can you think of any specific
examples of a population?
Population Distribution
• Distribution - the arrangement of members of a
population in a certain area.

• Influenced by Abiotic and Biotic Factors.
• Define Abiotic and Biotic and give examples for
each.
Abiotic – Nonliving (ex. Light,
temperature, atmosphere)
Biotic – Living (ex. Food, bacteria, etc.)
3 Types of Distribution

• Clumped – Population is represented by
scattered groups of individuals.

• Uniform – Individuals are spread out.

• Random – No pattern in the spacing of
individuals.
4 Factors Controlling Population Size

• Natality (Birth) Rate – The number of births in a
population.

• Mortality (Death) Rate – The number of deaths
in a population.

• Immigration – The number of individuals
entering a population.

• Emigration – The number of individuals leaving a
population.
Growth Rate

• How do we define Growth Rate?

Birth Rate - Death Rate = Growth Rate
4 Stages of Growth Rate

1. Lag Phase – Slow Growth

2. Growth Phase – Fast Growth

3. Stationary Phase – No Growth

4. Death Phase – Decline in Growth
Factors Controlling
Population Phases
• List at least 2 factors that would lead to
each of the 4 phases of Growth Rate.

• Resources
• State of Environment
So what????

• What is the significance of all this
information?
Present Population
Earth’s population growth rates (per year):
• Africa – 2.5%
• Western Asia – 2.2%
• Southeastern Asia – 1.6%
• Central America – 2.3%
• East Asia – 0.9%
• Australia – 0.7%
• North America – 0.6%
• Europe – 0.1%
Consider this……….

• Earth’s population is increasing at a rate of
1.4%. Therefore, the population of Earth
now will double in…….
50 years.
Factors Affecting Human Population Size

Population change equation
Population
Change      =   (Births + Immigration) – (Deaths + Emigration)

Crude birth rate (BR)
Crude death rate (DR)
Refer to Figure 10-3, p. 177
U.S. Birth Rates: 1910-2100
Births per thousand population

32
30
28
26
24
22
20
18
End of World War II
16
Demographic
14                      Depression         Baby boom       Baby bust     Echo baby boom
transition
0
1910      1920       1930      1940      1950      1960     1970      1980    1990         2000      2010

Year

Fig. 10-8, p. 180
Population Age Structure
Male        Female

Rapid Growth         Slow Growth     Zero Growth   Negative Growth
Guatemala          United States      Spain         Germany
Nigeria             Australia        Austria       Bulgaria

Ages 0-14      Ages 15-44        Ages 45-85+
Fig. 10-14 p. 184
World Population Clock
US Population Clock
What can be done?

• Family Planning
• Government Regulation?
Population Notes
Part 2
Exponential Growth

“A rapid increase of a population.”
Represented by a “J Curve”

Can this trend
continue?
Limits to Exponential Growth

• As populations
begin to run out
of resources and
room, their
numbers begin to
level.
If there were no limiting factors, and
the population could continue to
grow forever, the curve would be J-
shaped.

BUT...
Because most populations have to
deal with limits (for example, running
out of food or space), they can only
increase to a certain point- this
leveling off of the population size
creates an S-shaped curve.
Carrying capacity (designated as
K) is the number of organisms of
one species that an environment
can support
Carrying capacity (K)

Exponential growth
Carrying Capacity
If population size is
under K, births will
exceed deaths,
population will
increase

But, if the population
size rises over K,
deaths will exceed
births, population will
decrease
Limiting Factors
• “An environmental condition that can limit
the maximum number of individuals in a
population.”

• Can be Density Independent or
Density Dependent.
Dependent vs. Independent

• Density Independent – Natural occurrences that
will happen no matter how large the population
is. Example – floods, fires, earthquakes, volcanic
eruptions, tsunamis, etc.
•   Density Dependent – Natural occurrences that
will happen due to a large number of individuals
in a population. Example – diseases, famine,
Interspecific & Intraspecific Competition

• Interspecific Competition – 2 populations
of the same/similar species overlap within
an ecosystem and compete for food/water
or other resources.

• Intraspecific Competition – 2 populations
of different species compete for resources.
K-Selective & R-Selective Populations

• K-Selective – individuals have a long life
span, fewer offspring, live in a stable
environment. Tend to have an S-curve
growth.

• R-Selective – individuals have a short life
span, lots of offspring, and live in a
selective environment.
Questions
• Why can’t the carrying capacity of Earth be
determined?

• 2 parents decide to have 6 kids. When the
parents die, what is the growth in that family?
What if they only had 2 kids?

• Why are humans growing exponentially each
year?
Question #1 – Humans are always changing and adapting
the environment, extending the carrying capacity.

Question #2 – The growth is +4 in that
family.
The growth is 0 in that
family

Question #3 – More babies are being born, less people
dying due to better health care, production of food,
improved way of life.

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