Population Dynamics by yurtgc548

VIEWS: 2 PAGES: 32

									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
   Saudi Arabia           Canada         Greece          Sweden

           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,
    resources gone, invader species.
       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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