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 period X 100

Task Come up with a list of factors that affect  Birth rate  Death 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 year X 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 year X 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 pyramid  Decreasing 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