POPULATION DENSITY

1
POPULATION DENSITY

• NUMBER OF INDIVIDUALS PER UNIT AREA

2
POPULATION CHARACTERISTICS

• Geographic distribution
• Density
• Growth rate
• Age Structure

3
POPULATION GROWTH

• Number of births
• Birth rategtDeath rate (increase)
• Birth rateDeath rate (same size)
• Number of deaths
• Birth rateltDeath rate (decrease)
• Number of individuals entering (immigration) and
  leaving (emigration) population

4
WORLD BIRTH/DEATH RATES

• Which continent is having greatest population
  growth?
• What is the population growth rate of the United
  States?
• Correlation between birth and death rates in
  particular parts of the world

5
COMPARING BIRTH/DEATH RATES

• Developing countries have high birth rates
• High birth rate Expectation that some will die
  because of the high infant mortality rate
• Help in looking after the farm
• Care for parents if they become old or sick
  there may not be a old age pension scheme
• Shortage of family planning facilities and advice

6
COMPARING BIRTH/DEATH RATES

• Developed countries have low birth rates
• Expensive to look after large families
• More women prefer to concentrate on careers
• Women have more control over their own fertility
• Ready availability of contraception and family
  planning advice

7
EXPONENTIAL GROWTH

• Reproduction of a population at a constant rate
• Initial slow growth
• Exponential growth would continue under ideal
  conditions with unlimited resources
• Bacteria colony growth

J CURVE
8
LOGISTIC GROWTH

• Growth slows/stops following a period of
  exponential growth
• Graph is S-shaped
• Point of graph where it levels off (roughly zero
  growth) is the carrying capacity (largest number
  of individuals environment can support)

9
THINK TANK

• 1200 penguins at beginning of year
• 1600 penguins at end of year
• WHAT WAS POPULATION GROWTH?
• During year 250 penguin chicks died
• WHAT WAS POPULATION GROWTH?
• During same year, 220 adults died
• WHAT WAS POPULATION GROWTH?

10
THINK TANK

• Define and/or describe how the following factors
  affect the size of a population

• birth rate)
• b. mortality ( death rate)
• c. growth rate
• d. immigration
• e. emigration
• Briefly describe exponential growth and what it
  looks like when graphed.
• Briefly describe logistic growth, and what it
  looks like when graphed. Define carrying capacity
  and describe how it affects logistic growth

11
LIMITS TO GROWTH

• Factors that cause population growth to decrease
• Density-dependent factors
• --competition
• --predation
• --parasitism
• --Disease

12
Density-Dependent Factors

• Strongly affect a large, dense population, NOT
  small, scattered populations as greatly
• Competition
• --food/water
• --space
• --sunlight
• Larger populations use up available resources
  faster than smaller ones

13
Density-Dependent Factors

• Predation
• Prey population decreases over time
• Predator decline will soon follow
• Lag time between decline an rise

14
Density-Dependent Factor

• Parasitism-Disease

15
Density-Independent Factors

• Affect all populations in similar ways,
  regardless of size
• Unusual weather, natural disasters, seasonal
  cycles, human activities

16
THINK TANK

• Identify as density-dependent or
  density-independent
• --flood
• --lack of food source
• --clear cutting forests
• --predation
• --parasitism

17
Human Population Growth

• Demography scientific study of human
  populations
• Age Structure Diagrams Show population by age
  and gender groups

18
THINK TANK

• Why might a contagious virus that causes a fatal
  disease be considered a density-dependent
  limiting factor?
• Using the age-structure, describe the population
  demographic transition of Sweden.