AP HUMAN GEO Unit 2 Review (EVERYTHING You NEED to Know!)

Main Ideas & Concepts Covered (AP Human Geo – Unit 2 Review / Module 2)

1) Population Distribution (Where People Live)

• Population = groups of people.
• Population distribution = the pattern of human habitation across Earth’s surface.
• People are unevenly distributed: some areas are sparsely populated, others are densely populated.

Two main factors explain distribution

Physical Factors

• Climate: harsh climates limit large concentrations of people.
  • Example: most of Australia is near the coast (moderate temperatures), while the interior is sparsely populated (dry/hot).
  • A common preference: mid-latitudes (30°–60°) due to milder temperatures and sufficient rainfall.
• Landforms:
  • Low-lying areas: easier to build and farm → more population.
  • Mountainous areas: often sparsely populated due to cold, low food availability, and thinner air.
  • Exception: near the equator, some mountains can be densely populated if they are cooler/temperate.
• Water bodies: settlements cluster near rivers, oceans, and lakes because water supports:
  • drinking
  • farming
  • transport and trade

Human Factors

• Culture: people may live where they feel cultural belonging or entitlement.
  • Example: cultural ties of Jews and Muslims to Israel/Palestine.
• Economy: people settle where jobs and resources are available.
  • Economic incentives can also drive migration.
  • Examples:
    • African slave trade (economic incentives to relocate enslaved people)
    • 19th-century immigration to the U.S. (unemployed Europeans seeking work)
• History: past settlement/migration patterns influence today’s distribution.
  • Examples:
    • Many Black Americans in the South due to slavery history
    • Nearly half of Asian Americans in the West due to ancestor migration/settlement
• Politics: people may move due to political dislike or political force.
  • Voluntary example: European immigrants in the 19th century fleeing oppressive regimes.
  • Forced example: Khmer Rouge (1975) forcing Cambodians from the capital to the countryside.

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2) Population Density (How Many People Live on a Land Area)

• Population density = how many people occupy a unit of land.
• Key distinction:
  • Distribution = where people live
  • Density = how many people live there

Methods of Calculating Population Density

1. Arithmetic Density

   • Formula: total population ÷ total land area
   • Includes all land, even uninhabitable areas.
   • Limitation: can suggest people are spread evenly when they aren’t.
   • Example: Taiwan
     • High arithmetic density, but most people live in a smaller portion of land.

2. Physiological Density

   • Formula: total population ÷ area of arable land (land suitable for agriculture)
   • Measures ability to support food needs.
   • Higher physiological density → more pressure on farmland; lower → less pressure.
   • Example: United Arab Emirates (UAE)
     • Arithmetic density seems moderate, but physiological density is extremely high due to limited arable land.

3. Agricultural Density

   • Formula: total number of farmers ÷ arable land area
   • Lower agricultural density can still be okay in wealthy countries due to mechanization.
   • High agricultural density often suggests many subsistence farmers.

Key message: No single metric tells the whole story—combine them for a fuller picture.

Why Density/Distribution Matters (Four Processes)

• Political: census data can change House seats and shift congressional power.
• Economic: population density influences spending on services and where businesses/infrastructure invest.
• Social: density affects access and cost-effectiveness of services (e.g., hospitals).
• Environmental / Natural resources:
  • growing populations increase demand for land and water.
  • Central concept: Earth’s carrying capacity = maximum population environment can support
  • Complicated by climate, agricultural productivity, technology, and unequal resource use.
  • Estimates vary widely (from hundreds of millions to over a trillion).

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3) Population Composition (Characteristics of Populations)

• Population composition = characteristics such as age, race, gender, etc.

A) Age Structure

• Age structure = population organized into age groups.
• Helps determine whether population is growing, stable, or declining.

Population Dependency Ratio

• Dependents: typically children under 15 and seniors over 65 (not usually working to support themselves).
• Shows pressure on working-age people.
  • Higher dependency ratio = fewer workers support more dependents.
  • Lower dependency ratio = more workers support fewer dependents.
• Formula (given):
  • (number of dependents ÷ number of working-age people) × 100

B) Sex Ratio

• Sex ratio compares males vs. females.
• Varies by scale:
  • Global: ~101 men per 100 women
  • Europe: ~95 per 100
  • China (example): ~110 per 100 (linked to one-child policy discussed in the video)

Population Pyramid

• Tool for comparing age structure and sex ratio.
• Y-axis: age increments (e.g., 5-year groups)
• X-axis: % of men and women
• Used to infer population trajectory from shape:
  1. Rapidly growing: broad base (many young people), high birth rates
     • Example: developing countries (e.g., Democratic Republic of Congo)
  2. Slow growth: narrower base than rapid growth but still pyramid-shaped
     • Example: China (one-child policy discussed)
  3. Stable growth: birth and death rates similar; more even distribution
     • Example: United States
  4. Population decline: narrower base than top (deaths exceed births)
     • Example: Germany; labor shortages and reduced consumer demand

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4) Population Dynamics (Trends in Growth/Decline)

Geographers examine three components:

1. Birth rates
2. Death rates
3. Migration

Birth Rate Measures (Fertility)

• General Fertility Rate (GFR):
  • Births per thousand people per year
  • Useful for predicting future growth.
• Total Fertility Rate (TFR):
  • Average number of children a woman will have during childbearing years (~15–49)
  • More accurate than GFR because it focuses on the population capable of giving birth.
  • Often reflects access to healthcare/family planning.
• Replacement level: TFR = 2.1 for stable population.
• Examples mentioned:
  • Europe ~1.5 (declining)
  • Africa ~4.3 (increasing)

Mortality Measures

• Mortality rate: overall death rate per thousand
  • globally around 8 per thousand, down from ~13 in 1960
• Life expectancy: average expected lifespan
  • Higher with better nutrition, medicine, and clean water.
  • Examples: ~80 years in rich developed countries vs. ~50 in many developing countries.
• Infant mortality rate:
  • deaths before age 1 per 1,000 live births
  • Often a stronger indicator of healthcare access than general child mortality.

Natural Increase (Combining Births and Deaths)

• Natural increase rate (RNI):
  • RNI = CBR − CDR
  • If positive → natural growth
  • If negative → natural decline
• Note: RNI excludes migration, so migration can still change total population size.

Population Doubling Time

• Time it takes for a population to double under current trends.
• Examples:
  • Ethiopia: ~27 years
  • United States: ~233 years

Factors That Influence Birth, Death, and Migration

• Social/cultural: especially gender roles and expectations for women
• Political: policies may encourage/discourage births; migration constraints/encouragement
  • Examples: China’s one-child policy; governments may expand benefits when populations shrink
• Economic:
  • birth rates tend to drop during downturns
  • migration increases when job opportunities rise
  • Example: 19th-century U.S. attracting European immigrants

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5) Theoretical Models of Population Change

A) Demographic Transition Model (DTM)

• Developed to explain European/American population patterns.
• Focuses on how fertility, mortality, and natural increase change across stages, driven mainly by industrialization.

Stages:

1. High stationary phase (pre-industrial/agrarian)
   • birth rate high, death rate high → stable or slight change
2. Early expansion
   • birth stays high; death drops sharply → rapid growth/demographic explosion
3. Late expansion
   • birth declines due to education/urbanization; deaths lower but births still exceed deaths → slower growth
   • Often associated with many developing countries today
4. Low stationary
   • birth and death similar → slow growth/stabilization
   • Often associated with developed countries; population aging concerns
5. Natural reduction (possible extra stage)
   • death exceeds birth → decline
   • Examples: some European countries and Japan

Migration can still increase population even in later DTM stages.

B) Epidemiological Transition Model (ETM)

• Focuses on how mortality changes due to disease patterns, not industrialization.
• Stages:
  1. Starvation
     • high mortality from infectious/parasitic diseases; low life expectancy
     • Example: Black Death spread (killed a quarter to half)
  2. Recession phase of pandemics
     • sanitation/nutrition/medicine reduce major epidemics
     • pandemics still occur; urban crowding accelerates spread
  3. Degenerative and man-made diseases
     • mortality low; life expectancy rises
     • chronic age-related diseases increase (heart disease, cancer)
  4. Delayed phase of degenerative diseases
     • highest life expectancy; improved medical tech for aging-related illnesses
  5. Re-emergence phase of infectious diseases
     • infectious diseases adapt; antibiotic resistance leads to renewed threats; life expectancy decreases

Main criticism:

• oversimplifies disease causes across different times/places
• does not adequately address poverty as a major driver of disease spread and mortality differences

C) Malthusian Theory (Population vs. Resources)

• Malthus argued:
  • population grows geometrically
  • food grows arithmetically
  • this would lead to starvation/epidemics unless people delay marriage/have fewer children
• Video conclusion: Malthus was “wrong” because technology (mechanized farming, fertilizers) helped food production keep pace with population growth.

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6) Consequences of Population Growth/Decline

Government Responses (Population Policy)

• Anti-natalist policies (reduce births)
  • Example: China’s one-child policy
• Pro-natalist policies (increase births)
  • used to counter aging-related labor shortages
  • tools mentioned: parental leave, free childcare, reducing costs of raising children
• Immigration policies to manage migration-driven population change
  • Example: Western Europe post-WWII inviting immigrants during economic recovery

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7) Women’s Changing Roles and Demographic Effects

• As women gain:

  • education
  • healthcare
  • contraception
  • autonomy birth rates tend to decrease.

• Conversely, traditional gender roles (women primarily as homemakers/childbearers) tend to produce more children.

Three Ways to Increase Women’s Role (and Reduce Birth Rates)

1. Access to education (“more books, fewer children” principle)
2. Access to family planning (birth control pills, IUDs)
3. Access to employment (postponed marriage/childbearing for career)

Broader Effects Beyond Fertility

• Mortality: fewer children can mean improved infant survival (implied lower infant mortality)
• Migration: referenced Ravenstein’s laws of migration (Law #6 noted):
  • women more likely to migrate within their own country
  • men more likely to migrate internationally
  • rural-to-urban migration is common

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8) Population Aging: Causes & Consequences

• Population aging features:
  • rising dependency ratio
  • lower total fertility rate (below ~2.1)
• On a population pyramid: middle cohorts are larger than lower cohorts.

Causes

• fertility rates
• mortality rates
• longer life expectancy

Consequences

1. Political: older voters shape policy priorities
   • Example: social security/healthcare focus in the U.S.
2. Social: fewer people available to care for elders at home (nuclear families)
   • more elderly in retirement/nursing homes
3. Economic: fewer workers and more retirees → tax base strain
   • Example concern mentioned: Social Security fund exhaustion forecast by 2031

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9) Migration (Causes, Types, Consequences)

Immigration vs. Emigration

• Immigration: coming into a country
• Emigration: leaving a country

Push vs. Pull Factors

• Push factors: negative conditions in the origin
  • war/persecution (refugees)
  • famine/natural disaster (e.g., Hurricane Katrina)
• Pull factors: positive opportunities in the destination
  • jobs
  • more stable government
• Migration often results from a combination of push and pull factors.

Intermediate Obstacles/Opportunities

• Obstacles: barriers encountered during travel
• Opportunities: unexpected chances that can change where someone settles

Five Categories of Migration Factors (Push/Pull/In-Between)

• Cultural: persecution/identity conflict
  • Example: India partition after WWII—Muslims north to Pakistan; Hindus south to India
• Demographic: lack of services in rural areas; city overcrowding; insufficient jobs
• Economic: job seeking
  • Example: Bracero Program (Mexican workers filling U.S. labor needs)
• Environmental: climate differences or disasters
  • Example: moving to Florida to escape cold winters
• Political: war and instability
  • Example: Syrian civil war (from 2011) → millions fled

Types of Migration

• Forced migration: leaving against one’s will

  • examples:
    • slavery
    • refugees fleeing war/persecution (right to seek asylum under international law)
    • internally displaced persons (same country, different area)

• Voluntary migration (7 listed categories)

  1. Transnational: maintain strong cultural ties across borders (often remittances)
  2. Transhuman: nomadic groups; movement is part of lifestyle
  3. Internal migration: within-country movement (often shorter distances)
  4. Chain migration: earlier migrants encourage others; networks expand settlements
     • Example: Irish famine-driven migration waves
  5. Staged migration: moving in steps with temporary stops
  6. Guest workers: temporary labor migration to fill jobs for a set period
     • Example: Bracero Program
  7. Rural-urban migration: rural-to-urban movement; increasing since the Industrial Revolution

Consequences of Migration (Three Categories)

1. Political
   • can change political power distribution (e.g., North/Midwest → Sun Belt shifts)
   • may cause restrictive policies if natives resent newcomers
   • Example: Chinese Exclusion Act of 1882 (10-year ban)
2. Economic
   • destination country benefits from labor (often lower-wage jobs natives avoid)
   • key sectors mentioned: agriculture and construction
   • origin country impacts:
     • “brain/workforce” outflow (possible slow growth)
     • remittances (World Bank estimate mentioned: $630B+ in 2022)
3. Cultural
   • destination: more exposure to language/religion/music
     • Example: Mexican food popularity in the U.S.
   • origin: remittances improve living standards, but family separation can strain social structures and worsen dependency burdens

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Speakers / Sources Featured

• Steve Heimler (main speaker; host/creator of the Heimler Review content)