Ch36: Demographic Trends Higher Human Biology

Why do populations increase & decrease? A population is a group of individuals of the same species which makes up part of an ecosystem. Population size varies and is affected by : births deaths immigrants emigrants The study of population change and the factors that cause these changes is called population dynamics.

Population Change br = Birth rate dr = death rate ir = immigration rate er = emmigration rate Per 1000 population Change in population size = (br + ir) – (dr + er) So Change in population size = br – dr + ir - er

Comparing a developing & developed country The difference between br and dr increases so the population increases The difference between br and dr decreases so the population decreases

Demographic Transition Model This model relates rate of population growth with cultural development. As a country develops it passes through 4 stages: Early Expanding population 2 Late Expanding population 3 Stable population 1 Stable population 4

Population Pyramids A population pyramid represents the structure of a population in terms of the age and sex of the population at one time.

Anticipating future needs Population pyramids can: allow prediction of future population structure indicate the needs of future generations education e.g. water transport Health care electricity

Developing country – Government strategies Invest in: Medical care build hospitals, promote family planning, provide birth control Education – build schools Employment – training programs Nearly 50% population are young dependents under 16 Less investment in care of the elderly

Developed country – Government strategies Invest in: Health care for elderly Housing for elderly old folk’s homes sheltered housing More hospitals Geriatric hospitals Large elderly population Small proportion of young people No need to build many new schools

Gender Imbalance in Developed countries More females in the elderly population Women tend to live longer than men. The higher death rate in men could be due to: Stress Smoking Excessive alcohol Lack of exercise This difference is now getting less possibly due people adopting healthier lifestyles.

Population Control Although the population of many developed countries is now stable, the population of developing countries is increasing rapidly. If this continues the Earth will reach its carrying capacity and limiting factors will have a regulatory effect by increasing the death rate.

Population Control : Deer When a small population of deer come across an uninhabited grassy island free of predators the population explodes reaching the environment’s carrying capacity. Image source: www.guardian.co.uk If the population exceeds the carrying capacity the environment will become damaged and the deer population goes into ‘free fall’ decreases rapidly. The population then stabilises at a lower carrying capacity. If the environment recovers the carrying capacity increases again.

Population Control: Birth Control Birth control is considered the most humane & and realistic option to control the human population. But some people are choose not to use birth control because of: Religious beliefs Economic situation – in poor countries children are considered cheap labour needed to support the family Poor medical care – if child mortality is high, large families guarantee some children will survive Cultural & Social backgrounds - in poor societies large families are needed so that some children survive to look after the parents in their old age.

Population Control: Birth Control Birth control is more commonly used in developed countries because: Educational opportunities – Longer schooling tends to result in a decrease in birth rate as women seek career opportunities Degree of status – Women who have more control over their own lives choose to marry later and use contraception.

Population Control: Moral dilemma Energy Consumption USA use 30% of the world’s energy 6% of world population Is it fair? India use 2% of the world’s energy 20% of world population

Population Control: Moral dilemma In a lifetime… The average American consumes 40 x as much of the Earth’s resources as the average Asian Is it immoral to try to impose birth control on the people in developing countries when wealth & the use of resources is so unequal?

Population Control: Situation in Developing countries Family planning helps couples make a conscious effort to regulate the number & timing of new births. Governments of most countries support programmes of family planning. But to be successful they must be combined with social & economic developments to give families security.

Population Control: The future What will happen if the world’s population continues to grow at the present rate? Despite… increased deaths due to AIDs decreased birth rate due to use of contraception … the population will still rapidly increase!! A global solution is needed!