1. Ch36: Demographic Trends
Higher Human Biology

2. 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.

3. 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

4. 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

5. 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

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

7. 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

8. 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

9. 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

10. 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.

11. 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.

12. 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:
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.

13. 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.

14. 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.

15. 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

16. 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?

17. 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.

18. 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!