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
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
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
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
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
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).