APES 2.1 - Human Population Dynamics

Lesson 2.1

• Explain age structure diagrams (population pyramids)
• Explain how human populations experience growth and decline.
• Explain factors that affect total fertility rate (TFR) in human populations.

Human Population Dynamics

START HERE: Interpreting Age Structure Diagrams

EXPANDING

STABLE

DECLINING

Rule of 70

Population Math:

A stable population is at replacement-level fertility.

Total Fertility Rate (TFR) is the average number of children born to a woman over her lifetime. TFR for a country is impacted by:

• the age at which a woman has her first child (lower in developing countries)
• educational opportunities for females (women who go to college tend to have children later)
• access to family planning (contraceptives, etc.)

Replacement-level fertility is usually around 2 (two children replaces the couple that had them) but globally, it is higher - 2.1. The extra 0.1 accounts for children that die before reaching childbearing age. Something to think about: What would replacement-level fertility be for a country that has a high infant mortality rate?

Interpreting Age Structure Diagrams

• The shape of an age structure diagram (also called a population pyramid) can be used to infer how a population size will change.

• A rapidly growing population will have a higher proportion of younger people compared to stable or declining populations.

• A population pyramid can only show percentages of each age cohort. It DOES NOT show total population size!

GROWING

STABLE

What limits the growth of populations?

Density-Dependent Limiting Factors

Density-Independent Limiting Factors

• The impact of these depends on the amount of people present

• Also applies to other living things besides humans!

• Access to clean water and air, food availability, disease transmission, territory size

• Does not depend on the amount of people present.

• Also applies to other living things besides humans!

• Major storms, fires, heat waves, droughts

It is very important to note that human populations don't always shrink because something bad happens! In many scenarios, especially in wealthy countries, humans choose to have few or no children (TFR <2), so the population begins to decline.

Basic Population Formulas

• These are not provided on the AP test, so you will need to memorize them.

What causes populations to grow?

Birth Rate > Death Rate

Low Infant Mortality Rate

• Infant Mortality refers to the number of deaths per 1,000 live births that occur before the first birthday.

• Access to quality health care for the mother and infant improves infant mortality rate.

• Typically, birth rates are high due to cultural factors.

• Birth rate tends to be higher in developing countries where access to contraception is limited.