Chapter 5- Populations
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Transcript of Chapter 5- Populations
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Chapter 5- Populations
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How many people are in the world?
6.7 Billion
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Population Density of the World
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World Population over Time
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Important Characteristics Geographic distribution Density Growth Rate
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Important CharacteristicsGeographic distribution- area that
is inhabited Density Growth Rate
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Important Characteristics Geographic distributionDensity- number of individuals
per unit area Growth Rate
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Important Characteristics Geographic distributionDensity- number of individuals
per unit area Growth Rate
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Important Characteristics Geographic distribution DensityGrowth Rate- how fast the
population grows
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Growth Rates
Population size is determined by Number of births
Number of deaths
Number of individuals that enter or leave the population
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Growth Rates
Birth rate- how many are born Baby Boom
Death rate- how many die Black Plague
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Growth RatesBirth Rate Death Rate Overall Rate
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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?
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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?
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What limits a population’s growth?
-ability to reproduce quickly-nutrients-space-water
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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?
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Exponential Growth
When a population reproduces at a constant rate. This occurs only under ideal conditions with unlimited resources.
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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
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Carrying capacity
Carrying capacity- The largest number of individuals that an environment can support
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Limits to growth
Limiting factor- a factor that causes population growth to decrease
CompetitionPredationParasitism and diseaseHuman disturbancesDrought and other climate extremes
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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
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Density-dependent limiting factor Predation
predator-prey relationship
Parasitism and Disease
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Density-Independent FactorsDensity-Independent Factors- affect all
populations, regardless of size
Unusual weatherNatural disastersSeasonal cyclesHuman activities- damming rivers and
clear-cutting forests
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Human Population Growth
Demography- the scientific study of human populations
Demographic transition- a dramatic change in birth and death rates
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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
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Age Structure
Age-Structure Diagram- graph of the numbers of people in different age groups
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Future Population Growth How many people can the world
support?
What are the things that people need to live?
-food -water -housing -jobs
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Future Population GrowthResources vs. Population