Ch36: Demographic TrendsCh36: Demographic Trends

Higher Human BiologyHigher Human Biology

Why do populations increase & Why do populations increase & decrease?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

The study of population change and the factors that cause these changes is called population dynamics.

• immigrants• emigrants

Population Population ChangeChangebr = Birth rate

dr = death rateir = immigration rateer = emmigration rate Change in

population size

Per 1000 population

= (br + ir) – (dr + er)

br – dr + ir - erChange in population

size =

So

Comparing a developing Comparing a developing & developed country& 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 ModelDemographic Transition ModelThis model relates rate of population growth with cultural development. As a country develops it passes through 4 stages:

Stablepopulation

1

Early Expanding population

2

Late Expanding population

3

Stablepopulation

4

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

Anticipating future needsAnticipating future needsPopulation pyramids can:

e.g.

transport

Health care

education

water

electricity

• allow prediction of future population structure• indicate the needs of future generations

DevelopDevelopinging country – country – Government strategiesGovernment strategies

Invest in:

Nearly 50% population are young dependents

under 16Less investment in care of the elderly

•Medical care build hospitals,promote family planning, provide birth control

•Education – build schools•Employment – training programs

DevelopDeveloped ed country – country – Government strategiesGovernment strategies

No need to build many new

schools

Small proportion of young people

Invest in:• Health care for elderly• Housing for elderly

old folk’s homes sheltered housing

• More hospitals Geriatric hospitals

Large elderly population

Gender Imbalance Gender Imbalance in Developed in Developed

countriescountriesWomen tend to live longer than men. The higher death rate in men could be due to:• Stress• Smoking• Excessive alcohol• Lack of exerciseThis difference is now getting less possibly

due people adopting healthier lifestyles.

More females in the elderly population

Population ControlPopulation ControlAlthough 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 : DeerPopulation Control : DeerWhen a small population of deer come across an uninhabited grassy island free of predators the population explodes reaching the environment’s carrying capacity. If the population exceeds the carrying capacity the environment will become damaged and the deer population goes into ‘free fall’ decreases rapidly.

Image source: www.guardian.co.uk

The population then stabilises at a lower carrying capacity. If the environment recovers the carrying capacity increases again.

Birth control is considered the most humane & and realistic option to control the human

population.

• 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 ControlPopulation Control: Birth Control

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

Population Control: Population Control: Birth ControlBirth 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.

India

Energy Consumption

Population Control: Population Control: Moral dilemmaMoral dilemma

6% of world

population

use 30% of the world’s

energy

Is it fair?

20% of world population

use 2% of the world’s

energy

USA

Population Control: Population Control: Moral dilemmaMoral 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?

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: Population Control: Situation in Developing Situation in Developing

countriescountries

Despite…• increased deaths due to AIDs• decreased birth rate due to use of contraception

Population Control: The futurePopulation Control: The future

… the population will still rapidly increase!!

A global solution is needed!

What will happen if the world’s population continues to grow at the

present rate?