1. Populations

1.6 Human Populations

Starter

Human population has doubled in the last 50 years and is now over 6 billion. What factors have led to this explosion of population?

The development of agriculture The development of manufacturing (the

industrial revolution)

Learning Objectives

Describe how the human population growth curve differs from most other organisms

Explain what factors affect the growth and size of human populations

Success Criteria You can describe factors affecting birth and

death rates You can explain population pyramids

Human population size and growth rate

Factors affecting the growth and size of human populations The balance between birth and death rate

determines if human population increases or decreases

Individual populations are affected by migration immigration (individuals join a population

from outside)emigration (individuals leave a population)

Working out population growth

Population growth = (births + immigration) – (deaths + emigration)

Percentage population growth rate in a given period = population change during the period

population at the start of the periodX 100

Task

Come up with a list of factors that affectBirth rateDeath rate

Factors affecting Birth Rates Economic conditions: countries with a higher per

capita income tend to have lower birth rates Cultural and Religious backgrounds: some countries

encourage larger families and some religions ban oppose birth control

Social pressures and conditions: a large family improves social standing in some countries

Birth control: birth rates depend on the availability and use of birth control

Political factors: Education and tax policies can influence birth rates

Birth rate equation

Birth rate = number of births per year

total population in the same yearX 1000

Factors affecting Death Rates Age profile: higher proportion of elderly people means a higher

death rate Life expectancy: those in economically developed countries

live longer Food supply: enough food and a balanced diet reduce death

rate Safe drinking water and effective sanitation: reduce death

rate by reducing diseases such as cholera Medical care: access to healthcare decreases death rate Natural disasters: some areas are more prone to drought or

famine War: decreases the number of fertile adults in addition to

raising the death rate

Death rate equation

Death rate = number of deaths per year

total population in the same yearX 1000

Population structure Societies change as life expectancy

increases and birth rates decrease. This is called demographic transition.

Population pyramids can show:Stable population: no change in population

size Increasing population: high birth rate, wider

base to the pyramidDecreasing population: lower mortality and

birth rates, wider apex to the pyramid

Task

Work through the Application questions on pages 22 – 23 of the textbook

Answers

1. a) Stage 3

b) Stage 1

c) Stage 2

d) Stage 1

e) Stage 4

2. Pyramid A represents stage 4 because there is a low birth rate (narrow pyramid base) and a low death rate (sides are fairly vertical and many people live beyond 65 years).

Pyramid B represents stage 2 because there is a high birth rate (wide pyramid base) and a falling death rate (slides slope upwards and some, but not many, people live beyond 65 years).

Learning Objectives

Describe how the human population growth curve differs from most other organisms

Explain what factors affect the growth and size of human populations

Success Criteria You can describe factors affecting birth and

death rates You can explain population pyramids