IB ESS Human population

1. HUMAN POPULATION
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2. •3.1.-Population Dynamics
•3.1.1-Describe the nature and explain the implications of exponential growth in human populations.
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3. This question is difficult to answer.
•Estimates are usually based on food, but human agriculture limits assumptions on available amounts.
•Human population growth rate has been growing more than exponentially.
What is the carrying capacity of Earth for humans?
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4. HUMAN POPULATION GROWTH
1999
1975
domestication of plants, animals 9000 B.C. (about 11,000 years ago)
agriculturally based urban societies
beginning of industrial, scientific revolutions
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5. What is HUMAN POPULATION?
•The total number of persons inhabiting a country, city, or any district or area.
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6. What is Exponential growth?
•Exponential population growth is when the birth rate is constant over a period of time and isn't limited by food or disease
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8. Measures of population changes are
1.Crude Birth Rate
2.Crude Death Rate
3.Rate of Natural Increase
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9. What is CRUDE BIRTH RATE?
•Crude birth rate is the childbirths per 1,000 people per year. This is a common measure of fertility for a given population.
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10. •Therefore, the formula for crude birth rate is
The crude birth rate = number of births per year x 1000
Total population
Example.
In 2007, there were 3,250 births in a city with population of 223,000. Therefore: CBR = 3,250 x1000
223,000
CBR =14.57
So, there were 14.57 births for every 1,000 people in the city.
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11. •The crude birth rate could be of concern for particular countries who may be experiencing population decline, or for national governments who are worried about population growth rates that are higher than their country can sustain
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16. •The birth rate is usually the dominant factor in determining the rate of population growth. It depends on both the level of fertility and the age structure of the population.
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17. CRUDE DEATH RATE
•The death rate, while only a rough indicator of the mortality situation in a country, accurately indicates the current mortality impact on population growth.
•This indicator is significantly affected by age distribution, and most countries will eventually show a rise in the overall death rate, in spite of continued decline in mortality at all ages, as declining fertility results in an aging population.
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18. How to calculate Crude Death Rate?
The crude death rate = number of death per year x 1000
Total population
Example.
In 2007, there were 4,000 death in a city with population of 2,000,000. Therefore: CBR = 4,000 x1000
2,000,000
CDR =2
So, there were 2 death for every 1,000 people in the city.
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23. Rates of Global Pop. Change
•CBR (crude birth rate) = number of births per 1000 population
–1990: 24 Today: 21.3
•CDR (crude death rate) = number of deaths per 1000 population
–1990: 9 Today: 8.93
•Growth rate = birth rate - death rate (often in %)
–1990: 1.5% Today: 1.3%
–growth rates have come down
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24. Special Kinds of Fertility and Mortality Rates
•TFR (total fertility rate) =
–number of children born to a woman during her reproductive years (or life time)
–1990: 3.1 2000: 2.8
•IMR (infant mortality rate) =
–infant deaths per 1000 live births (infant < 1 yr)
–1990: 62 2000: 56 (1900: 200)
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25. RECAP
What is Human population?
What is Crude Birth Rate? Formula
What is Crude Death Rate? Formula
What is Exponential growth?
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26. Population, population change, growth rates
•Population: number of persons
•Population change: increase in the number of persons (per year)
•Growth rates: rate of change (per year)
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30. Doubling Time
Doubling time (T) = 70 .
annual percentage rate
Doubling time (T) = 70 . = 50 years
1.4
Doubling time = the number of years it would take a population to double its size at its current growth rate.
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31. Doubling Time
•Number of years in which a population reaches twice its size
•Doubling time can be approximated using growth rates
•doubling time = 70 : growth rate
–rate: 1.4 doubling time: 49
–rate: 2.0 doubling time: 34.5
–rate: 0.5 doubling time: 138
–rate: -0.5 doubling time: ????
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32. How to calculate Rate of Natural Increase?
•The rate of natural increase shows the rate at which people are added to a given population by births and deaths (ignoring migration). It is usually represented as follows:
•Rate of Natural Increase
Crude Birth Rate - Crude Death Rate
10
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33. For example,
Madagascar's crude birth rate 37.89
The crude death rate 7.97
37.89 -7.97
10
29.92 =2.992%
10
divide that by 10 and the result is 2.992%, Madagascar's rate of natural increase
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34. Why has the world’s population grown at such different rates throughout history?
Natural increase = births – deaths
Net migration = immigrants – emigrants
•Births
•Deaths
•Migration
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35. What is mortality?
•Mortality rate is a measure of the number of deaths (in general, or due to a specific cause) in a population, scaled to the size of that population, per unit of time
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36. What is fertility rate ?
•The total fertility rate (TFR), sometimes also called the fertility rate, period total fertility rate (PTFR) or total period fertility rate (TPFR) of a population is the average number of children that would be born to a woman over her lifetime
•The number, which ranges from more than 7 children per woman in developing countries in Africa to around 1 child per woman in Eastern European and highly-developed Asian countries.
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37. Births per woman
< 2
2-2.9
3-3.9
4-4.9
5+
No
Data
Fertility Rates
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38. What affects fertility rates?
•Importance of children to labor force
•Urbanization
•Cost of raising and educating children
•Education and employment options for women
•Average age of marriage
•Availability of pension plans
•Availability of legal abortions
•Availability of birth control
•Religious beliefs, traditions and culture
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39. What affects death rates?
•Higher food supplies
•Better nutrition
•Improved medical and health technology
•Improved sanitation
•Safer water supplies
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40. Indicators of overall health
Growth = natural increase – net migration
•Life expectancy
•Infant mortality
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41. Infant deaths
per 1,000 live births
<10
<10-35
<36-70
<71-100
<100+
Data not available
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42. Population
(2002)
Population
projected
(2025)
Infant mortality rate
Life
expectancy
Fertility rate (TFR)
%Population under age 15
% Population
over
age 65
Per capita GNI PPP (2000)
288 million
174 million
130 million
346 million
219 million
205 million
6.8
33
75
77 years
69 years
52 years
2.1
2.2
5.8
21%
33%
44%
13%
5%
3%
$34,100
$7,300
$800
United States (highly developed)
Brazil (moderately developed)
Nigeria (less developed)
© 2004 Brooks/Cole – Thomson Learning
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43. Developed Countries
50
40
30
20
10
0
1775
1800
1850
1900
1950
2000
2050
Rate per 1,000 people
Year
Rate of natural increase
Crude
birth rate
Crude
death rate
Rate of natural increase = crude birth rate – crude death rate
© 2004 Brooks/Cole – Thomson Learning
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44. Developing Countries
50
40
30
20
10
0
1775
1800
1850
1900
1950
2000
2050
Rate per 1,000 people
Crude
birth rate
Rate of natural increase
Crude
death rate
Year
© 2004 Brooks/Cole – Thomson Learning
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46. Age Structure
•Age structure—the proportion of the population in each age class.
•Age structure influences whether a population will increase or decrease in size.
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47. Age Structure
•Countries that have high rates of growth usually have more young people than older people.
•In contrast, countries that have slow growth or no growth usually have an even distribution of ages in the population.
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48. Age Structure
•Age structure can be graphed in a population pyramid, a type of double sided bar graph.
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49. Age-Structure Diagrams
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51. Population Pyramids
•Graphic device: bar graph
•Shows the age and gender composition of a region
•Horizontal axis: gender
–male: left-hand female: right-hand
–absolute number of people or %
•Vertical axis: age
–5-year or 10-year age groups
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52. •A population pyramid, also called an age structure diagram, is a graphical illustration that shows the distribution of various age groups in a population which forms the shape of a pyramid when the population is growing.
What is Population Pyramid?
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53. •It show how many individuals are alive in different age groups in a country for a given year.
•They also show how many are male and female.
•Population numbers are always on the x-axis and age groups on the y-axis.
•The overall stage can depict the stage of development of the country at a particular time.
• LEDC’s tend to have expanding populations so they are wide at the bottom, whereas MEDC’s tend to have stationary or contracting pyramids as birth rates fall and individuals live longer.
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54. Stage 1: High birth rate; rapid fall in each upward age group due high death rates; short life expectancy.
Stage 2: High birth rate; fall in death rate as more living to middle age; slightly longer life expectancy.
Stage 3: Declining birth rate; low death rate; more people living to old age.
Stage 4: Low birth rate; low death rate; higher dependency ratio; longer life expectancy.
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55. •It typically consists of two back-to-back bar graphs, with the population plotted on the X- axis and age on the Y-axis, one showing the number of males and one showing females in a particular population in five-year age groups
•Males are conventionally shown on the left and females on the right, and they may be measured by raw number or as a percentage of the total population.
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57. Describe and explain the main features of the population pyramid below
This population pyramid has a very wide base showing that there are a lot of babies born every year. This shows that there is a good medical service within the country. The different sectors from 5 - 9 up to 25 - 29 decreases very quickly and decreases even more quickly on the male side. This is good for the country, as there are fewer people to feed and educate. As the ages increase up through the pyramid, it gets narrower and narrower. This might be because as people get older they leave the country in search of a job or a better standard of living
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58. 3.1.3-
•Analyse age/sex pyramids and diagrams showing demographic transition model
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59. How can economic development help reduce birth rates?
•Demographers have developed a hypothesis known as the DEMOGRAPHIC TRANSITION.
•It states that as countries become industrialized, first death rates go down and then their birth rates decline.
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60. AUGUST SUMMATIVE
•Date :3.09.2013
•Total Marks :45(IB Format)
•Time : 1 hour
•Syllabus :Human Population
•Unit :3.1.1, 3.1.2, 3.1.3 & 3.1.4
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61. AUGUST FORMATIVE
•Human Population Worksheet
•Total Marks :40
•Will be given today
•Due date : 29:08:2013
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62. Demographic Transition
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63. •The "Demographic Transition" is a model that describes population change over time.
•The demographic transition model (DTM) is the transition from high birth and death rates to low birth and death rates as a country develops from a pre-industrial to an industrialized economic system.
What is Demographic Transition?
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64. Stage 1 - High Fluctuating
Stage 2 - Early Expanding
Stage 3 - Late Expanding
Stage 4 - Low Fluctuating
Stage 5- Only Possible in some countries
FIVE STAGES IN DTM
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66. Birth Rate is high as a result of:
1.Lack of family planning
2.Need for workers in agriculture
3.Religious beliefs
Death Rate is high because of:
1.High levels of disease
2.Famine
3.Lack of health care
4.War
5.Lack of education
Stage One-DTM
Both high birth rates and death rates fluctuate in the first stage of the population model giving a small population growth. There are many reasons for this:
Typical of Britain in the 18th century and the Least Economically Developed Countries
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67. •Birth Rate remains high. Death Rate is falling. Population begins to rise steadily.
•Reasons
Death Rate is falling as a result of:
1.Improved health care (e.g. Smallpox Vaccine)
2.Improved Hygiene (Water for drinking boiled)
3.Improved sanitation
4.Improved food production and storage
•Typical of Britain in 19th century; Bangladesh; Nigeria
STAGE TWO-DTM
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72. Birth Rate starts to fall. Death Rate continues to fall slowly. Population rising.
Reasons:
1.Family planning available
2.Lower Infant Mortality Rate
3.Increased standard of living
4.Changing status of women
•Typical of Britain in late 19th and early 20th century; China; Brazil
STAGE THREE-DTM
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76. •Both birth rates and death rates remain low, fluctuating with 'baby booms' and epidemics of illnesses and disease. This results in a steady population.
Typical of USA; Sweden; Japan; Britain
STAGE FOUR-DTM
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79. •A stage 5 was not originally thought of as part of the DTM, but some northern countries are now reaching the stage where total population is declining where birth rates have dropped below death rates.
• One such country is Germany, which has taken in foreign workers to fill jobs.
STAGE FIVE-DTM
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80. Area
Birth Rate
Reason
Death Rate
Reason
LEDCs
High
No contraception Couples have many babies to compensate for the high death rate caused by poor health care Large families need to work on the land to contribute to family income Children look after old Religious reasons
High
Poor medical facilities Disease Poor nutrition High Infant mortality
NICs
High/ Decreasing
People are used to having many children. Takes time for culture to change Changing status of women
Decreasing
As an economy develops money becomes available for better health care Housing improves Better childcare
MEDCs
Low
Children are expensive People know their children are going to survive so they can keep their families small Widely available contraceptives Changing status of women
Low
Better health care Better standard of living
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82. What are the main factors that affect the growth of a population?
 The main factors that make populations grow are births and immigration.(The action of coming to live permanently)
 The main factors that make populations decrease are deaths and emigration.(moving from one place)
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83. •Two types of population curve
•S Population Curve
•J Population Curve
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84. TYPES OF POPULATION CURVE
•Two modes of population growth.
•J-Shape curve is also known as- Exponential curve occurs when there is no limit to population size.
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86. •S-Shape curve is also known as - Logistic curve shows the effect of a limiting factor
•S-Sigmoid
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87. What is S-Shaped Curve?
•In S - shaped or sigmoid growth the population show an initial gradual increase in population size in an ecosystem, followed by an exponential increase and then a gradual decline to near constant level.
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88. •In population of an ecosystem which factors determining the S shape curve?
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89. The curve obtained by plotting growth and time is called a growth curve. It is a typical sigmoid or S- shaped curve.
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90. What is J shaped?
•A curve on a graph that records the situation in which, in a new environment, the population density of an organism increases rapidly but then stops abruptly as environmental resistance
•It may be summarized mathematically as:
I. dN/dt = rN (with a definite limit on N)
II.where N is the number of individuals in the population, t is time, and
III.r is a constant representing the rate of increase for the organism concerned.
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91. •The growth of population is measured as increase in its size over a period of time and populations show characteristic patterns of growth with time.
• These patterns are known as population growth forms.
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93. What is Carrying Capacity ?
•Carrying Capacity is the maximum number of a species or load that can be sustainably supported by a given environment i.e without destroying the stock
•Population remain stable when the death rate and the birth rate are equal and so there is no net gain or reduction in population size
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95. Semester Syllabus
•Systems & Models
•The Ecosystem
•Conservation & Biodiversity
•Global Warming
•Human Population
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