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 Characteristics

Geographic 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 Rates

Birth 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

Predationpredator-prey relationship

Parasitism and Disease

Density-Independent Factors

Density-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 Growth

Resources vs. Population