Download - Chapter 5- Populations
Chapter 5- Populations
How many people are in the world?
6.7 Billion
Population Density of the World
World Population over Time
Important Characteristics Geographic distribution Density Growth Rate
Important CharacteristicsGeographic distribution- area that
is inhabited Density Growth Rate
Important Characteristics Geographic distributionDensity- number of individuals
per unit area Growth Rate
Important Characteristics Geographic distributionDensity- number of individuals
per unit area Growth Rate
Important Characteristics Geographic distribution DensityGrowth Rate- how fast the
population grows
Growth Rates
Population size is determined by Number of births
Number of deaths
Number of individuals that enter or leave the population
Growth Rates
Birth rate- how many are born Baby Boom
Death rate- how many die Black Plague
Growth RatesBirth Rate Death Rate Overall Rate
Growth Rates
Immigration- movement into area
Emigration- movement out of area
What causes people to immigrate or emigrate?
What causes bears to immigrate or emigrate?
Growth rates?
Where are the high birth rates in the world?
Where are the high death rates in the world?
Many developed nations have a negative growth rate. Why?
What limits a population’s growth?
-ability to reproduce quickly-nutrients-space-water
Growth limiting factors
Bacteria- divide every 20 minutesone day- 4,720,000,000,000,000,000,000
What is the reproduction rate for a mouse?
What is the reproduction rate for a human?
Exponential Growth
When a population reproduces at a constant rate. This occurs only under ideal conditions with unlimited resources.
Logistic growth
Logistic growth- occurs when a population’s growth slows or stops after exponential growth
Why does a population stop growing exponentially?
Birth rate decreases Death rate increases Immigration decreases Emigration increases
Carrying capacity
Carrying capacity- The largest number of individuals that an environment can support
Limits to growth
Limiting factor- a factor that causes population growth to decrease
CompetitionPredationParasitism and diseaseHuman disturbancesDrought and other climate extremes
Density-dependent limiting factor Density-dependent limiting factor-
depends on the population size
Competition- food, water, space, sunlight Same species Different species
Competitive exclusion principle No two species can occupy the same
niche in the same habitat at the same time
Density-dependent limiting factor Predation
predator-prey relationship
Parasitism and Disease
Density-Independent FactorsDensity-Independent Factors- affect all
populations, regardless of size
Unusual weatherNatural disastersSeasonal cyclesHuman activities- damming rivers and
clear-cutting forests
Human Population Growth
Demography- the scientific study of human populations
Demographic transition- a dramatic change in birth and death rates
Demographic transition
1. Birth rates stay same, Death rates decline
2. Birth rates decline, death rates stay low
Birth Rate Death Rate Overall Rate
Birth Rate Death Rate Overall Rate
Age Structure
Age-Structure Diagram- graph of the numbers of people in different age groups
Future Population Growth How many people can the world
support?
What are the things that people need to live?
-food -water -housing -jobs
Future Population GrowthResources vs. Population