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CHAPTER 8: POPULATION - Coggle Diagram
CHAPTER 8: POPULATION
8.2 Changes in population size
Population growth
Population = all organisms of one species living in an area
Exponential growth:
Growth rate increases rapidly
J-shaped curve
Population doubles repeatedly
Population growth curve
Lag phase
Organisms adapt to new environment
Growth is slow
Log (exponential) phase
Rapid population growth
Resources are plentiful
Stationary phase
Population reaches carrying capacity
Birth rate = death rate
Population stays almost constant
Carrying capacity
Maximum population an environment can support
Depends on:
food
water
shelter/resources
If exceeded:
food shortage
environmental damage
population may crash (example: reindeer on St Matthew Island)
Human population growth
10 000 years ago → about 5 million
Farming began (~6000 years ago)
more food
population increased
About 2000 years ago → 250 million
Took another 1800 years to reach 1 billion
1930 → 2 billion
1975 → 4 billion
2016 → over 7 billion
Birth rate
Total number of live births over time
Death rate
Total number of deaths over time
Rate of natural increase
Birth rate − death rate
2015:
Births ≈ 350 000/day
Deaths ≈ 150 000/day
Increase ≈ 200 000/day
≈ 73 million/year
Factors affecting birth rate
High birth rates
High infant mortality
Farming economies need workers
Children support families
Limited birth control
Low birth rates
Expensive to raise children
Pensions provided
Widespread contraception
Better education
Women delay marriage and childbirth
Migration
Population growth can also be affected by migration:
Population growth =
(births + immigration) − (deaths + emigration)
Immigration
People moving into an area
Emigration
People moving out of an area
Push factors (rural → urban)
Drought/famine
Poverty
Poor links with outside world
Poor services
Subsistence farming
Desertification
Sea-level rise
Seasonal weather events (monsoons, cyclones)
Pull factors (urban)
Reliable food supplies
Better-paid jobs
Good roads
Hospitals
Schools
Water
Electricity
Factory/shop/office work
8.3 Population structure
Population pyramid
Age
Sex
Number of males and females
Population groups
Young (0–16)
Dependent
Middle aged (16–65)
Independent
Working
Pay taxes
Old (65+)
Dependent
Types of population pyramids
Expanding population (LEDC)
Wide base
Many young people
High birth rate
Stationary population (MEDC example: USA)
Nearly rectangular
Birth rate and death rate similar
Declining population (Japan)
Narrow base
Low birth rate
Large elderly population
Effects of population structure
Young populations
Need more schools
Education is a priority
Ageing populations
Need hospitals
Need care homes
More money spent on elderly care
8.4 Managing human population size
Family planning
Helps couples choose:
when to have children
how many children to have
Includes:
contraception
sterilisation
abortion
IVF
Governments may provide contraception
Improved health and education
Health
Reduces infant mortality
Couples choose to have fewer children
Education
More knowledge of family planning
Women delay marriage
Women have fewer children
Better careers reduce family size
National population policies
Pronatalist policy
Purpose: Increase birth rate
Antinatalist policy
Purpose: Reduce birth rate
Methods
Family planning
Contraception
Education
Laws encouraging fewer children
8.1 Human population distribution and density
Population density
Number of people living in a place ÷ area
Average world density ≈ 50 people/km²
Density varies greatly:
Monaco = very high
Greenland = very low
USA average ≈ 33 people/km², but varies between states and even within states (example: Wyoming)
High density areas
Coasts
Near ports
Near fresh water
Low density areas
Deserts
Mountains
Population distribution
Describes where people live
Populations are spread unevenly
Some regions have very high populations while others have few or none