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AP Human Geo AMSCO 2.3

Population distribution

The pattern of where people live across Earth.

Population density

The number of people living in a specific area, usually measured per square kilometer.

Physical factors

Natural features that affect where people live, such as climate, water, elevation, and landforms.

Human factors

Human-made or social factors that affect population distribution, such as jobs, transportation, politics, and existing settlements.

Why do many people live near water?

Water provides drinking water, transportation, fertile land, and opportunities for trade and jobs.

Why are deserts and polar regions sparsely populated?

Extreme temperatures and limited water make it difficult to live there.

Population composition

The characteristics of a population, such as age and sex.

Population pyramid

A graph showing the age and sex composition of a population.

Cohort

A group of people who share a particular age range or characteristic.

Wide-base population pyramid

Shows a large young population, high birth rates, and rapid population growth.

Narrow-base population pyramid

Shows a smaller young population, lower birth rates, and slower or negative population growth.

Baby boom

A period when birth rates increase and a large generation is born.

Baby bust

A period when birth rates decrease and a smaller generation is born.

Echo

An increase in births caused when a large generation has children.

Birth deficit

A noticeable decrease in the number of people in an age group, often caused by war or another major event.

Migration anomaly

A change in the shape of a population pyramid caused by people moving into or out of an area.

Dependency ratio

A comparison of dependents to the working-age population.

Dependency ratio formula

(Young dependents + elderly dependents) ÷ working-age population × 100.

Young dependents

People ages 0–14.

Elderly dependents

People ages 65 and older.

Working-age population

People ages 15–64.

High dependency ratio

There are many dependents compared with the working-age population.

Carrying capacity

The largest population an environment can support with its available resources.

Overpopulation

When a population is larger than the environment can sustainably support.

Arithmetic density

Total population divided by total land area.

Arithmetic density formula

Population ÷ total land area.

Physiological density

The number of people supported by a country's arable land.

Physiological density formula

Population ÷ arable land.

Arable land

Land that can be used to grow crops.

Agricultural density

The number of farmers compared with the amount of arable land.

Agricultural density formula

Number of farmers ÷ arable land.

Clustered distribution

People live close together in groups or clusters.

Dispersed distribution

People are spread out over a large area.

Linear distribution

People are arranged along a line, such as a road, river, or coastline.

Infrastructure

Basic systems and structures needed for society, such as roads, transportation, water, and electricity.

Redistricting

Redrawing boundaries of political districts.

Daytime population density

Population density can increase during the day when people commute into an area for work or school.

Niger population pyramid

Niger has a wide-base pyramid, showing high birth rates, a large young population, and rapid growth.

Niger vs. United States

Niger has a younger, faster-growing population, while the United States has a more even age distribution and slower growth.

Arithmetic vs. physiological density

Arithmetic density uses all land; physiological density uses only arable land.

Arithmetic vs. agricultural density

Arithmetic density measures all people over all land; agricultural density measures farmers over arable land.