The document discusses the age-sex pyramid as a key tool for illustrating demographic characteristics of a population, including gender and age distribution. It outlines the different stages of the demographic transition model (DTM) that explain how birth and death rates change over time, from high rates in developing countries to low rates in developed ones. Additionally, factors influencing population pyramids are identified, such as fertility, migration, and health care advancements.

1. HGG1002
GEOGRAPHY OF THE HUMAN ENVIRONMENT:
Population systems :
Age Distribution

2. AGE SEX PYRAMID
DEF : This is a graphical illustration that outlines the most important
demographic characteristics of population which is the age sex
structure.
It also breaks down the country's or locations population into male
and female genders and age ranges.

3. D.T.M.
Relationship between DTM and Age-Sex Pyramids of the
population

4. Features :
1.Consists of two sides,
•The left side representing male population ,
•The right side representing female population
2.The pyramid starts from 0(O), it extends both directions to the left and
to the right respectively increasing in size or the proportion of the
population.
3. Along the vertical axis the pyramids display five year age increment
from birth at the bottom to old age at the top

5. Stage 1: High Birth rates and High Death rates.
High birth rates
•No birth control or family planning
•Many children die in infancy
•Many children born so as to labour for the family.
•Children are regarded as a sign of virility
•Religious beliefs encourage large families

6. High death rates
•Diseases and plagues (bubonic , cholera , kwashiorkor)
•Famine , uncertain food supplies and poor diet
•War
•Poor hygiene no piped water , clean water and no sewage disposal
•Little medical science , high doctor patient ratio.
•Competition for food
For example:
Least
economically
developed
countries
today:
Somalia, and
Britain in the
18th century

7. Stage 2: Birth rates remain high but Death rates fall rapidly
For example:
Britain in the
19th century,
Bangladesh
, Nigeria

8. The fall on death rates results from :
•Improved medical care – vaccinations , hospitals, doctors, new drugs and
scientific inventions.
•Improved sanitation
•Improvements in food supplies
•A decrease in child mortality.

9. Stage 3: Fall in both Birth rates and Death rates.
Usually as a result of :
•Improved economic conditions
•An increase in women status
•Access to contraception
•Increased mechanization reducing need for workers
•Increased standards of living

10. Stage 4 : Low fluctuating ,Low Birth rate and Low Birth rate
Due to
•Political stability
•Changes in personal lifestyles
•More women are in the workforce therefore less couples are having kids

11. Stage 5? : declining population
Theoretical
Death rate exceeds birth rates
Negative NIR (natural increase rate : crude birth rate – crude death rate)
Mostly eastern European countries are projected so :
Russia, Belarus Germany Italy Japan .
Most developed are predicted to experience population decline
•Factor of more elderly than young population in these countries
•Fewer young women who will be entering their child bearing years
•Elderly support ratio- the number of working age people (15-64)
divided by the number of persons 65 or older.

12. Factor affecting the population pyramids.
•Fertility
•Birth rate
•Death rate
•Migration (immigration and emigration)
•Disease out breaks
•Natural disasters

13. Presentation done by :
T. BERE – R164423S
T. SAMANYANGA – R164540T
T. MANGOSHO – R164538X
K.K. SADZAUCHI – R164430Z
M. MAFUMO – R164539K
J.J. MUKWEWA – R164525J
M.T. TSEKENI – R164424L
N. NYANDORO – R165832R
T. MADONDO – R165526Y
A. NYONI – R164522S
THE END