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Demography and
Population Growth
By Danilo Villar Rogayan Jr.Instructor I, Natural Sciences
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History of World Population
History of World Population
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History of World Population
Defining Populations
• Population –
is a group of
conspecifics
inhabiting a
specific place
at a specific
time
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Characteristics of Populations
• Geographic Distribution, or range,
describes the area inhabited by a
population
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Characteristics of Populations
• Population Density, the number of
individuals per unit area.
Characteristics of Populations
• Growth Rate, affected by the number of
births, number of deaths and the number
of individuals that enter or leave the
population.
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Characteristics of Populations
• Age Structure,
configuration of the
age of the
individuals in a
population
Defining Populations
• Demography – the quantitative description of
a population
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Defining Populations
• Demographers – concerned with the “vital
statistics” of a population: its size, its age and
sex composition, its spatial distribution, and
the like.
Population Density
• Population Density – calculated by
dividing the total number of individuals
by the total area they occupy
• ex.: 200 mice per hectare, 1 grizzly per
100 km2, 106 diatoms cm3
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Population Density
World Population Density 2010
people per square mi (mi2)
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Population Density
• Crude Density, measure of the number of
individuals per unit area across a study site
without regard to the variation in the quality of
the habitat.
• Ecological Density – number of individuals
per unit area of appropriate habitat.
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Techniques to Measure Density
• Census – direct tally of the number of
individuals in a study area
Techniques to Measure Density
• Estimates of
Absolute Density –
uses a sampling
scheme to
approximate the total
number of organisms
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World Population (as of December 1, 2016, 12:14 AM)
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World Population (as of December 1, 2016, 12:14 AM)
Philippine Population
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Population Calculation Population Density
( population ) = Population Density
area
Ex.:
270,000,000 people
9,166,605 sq. km.
29 people per square kilometer
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Population Calculation
Example:
Olongapo City is an autonomous city
with 12 800 square miles. There are
currently 320 000 inhabitants in the city.
Find the population density.
Population Calculation
Example:
320 000 / 12 800 =
25 people/sq.mi.
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Answer
1. 9 people per sq. km.
2. 3 cows per sq. mi
3. 9 dandelions per sq. m.
4. 5 167 dinoflagellates per sq.km.
Population Calculation
Birth or Death Rates
# of births or deaths per year = Birth or Death Rate
total population
NOTE: to find Crude Birth/Death Rates, multiply the rate by 1,000
Ex.: 23,452 births = 0.025 = 2.5% birth rate
942,721 people 25 = Crude Birth Rate
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Population Calculation
Example:
Castillejos is a third-class municipality of
Zambales with 13 750 sq. km. As of
yesterday, there are 16 760 people in the
town. Last year, there were 6 720 new
children born and 3 678 people were recorded
as deceased. What are the birth and death
rates?
Population Calculation
Example:
6 720 / 16 760 = 0.40
40 % birth rate
400 crude birth rate
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Population Calculation
Example:
3 678 / 16 760 = 0.22
22 % death rate
220 crude death rate
Population Calculation
Let’s Try.
1. Mautog City is a first-class city of Aklan with
25 890 sq. km. As of yesterday, there are 5
691 people in the city. Last year, there were
1678 new children born and 954 people were
recorded as deceased. What are the birth and
death rates?
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Answer
• 0.29 x 100
• Birth rate = 29%
• Crude birth rate = 290 people
Answer
• 0.17 x 100
• Death rate = 17%
• Crude death rate = 170 people
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Population Calculation
Let’s Try.
2. Lathegue City in Germany has a total area
of 568 543 sq. m. As of today, there are 269
074 population in the city. Data shows there
were 26 843 new children born and 17 531
people died this year. What are the birth and
death rates?
Answer
• 0.10 x 100
• Birth rate = 10%
• Crude birth rate = 100 people
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Answer
• 0.07 x 100
• Death rate = 7%
• Crude death rate = 70 people
Population Calculation
• FINDING POPULATION GROWTH RATE (r):
(This does not include immigration or emigration)
crude births – crude deaths = r %
10
40-30 = 1.0% OR
10
births – deaths X 100 = r%
total population
28,546 births – 24,389 deaths = 0.9%
455,387 total people
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Population Calculation
Example:
Castillejos is a third-class municipality of Zambales with 13 750 sq. km. As of yesterday, there are 16 760 people in the town. Last year, there were 6 720 new children born and 3 678 people were recorded as deceased. What is the population growth rate (r) ?
Population Calculation Example:
6720 – 3678 / 16 760 x 100 = r
3042 / 16 760 = 0.18 x 100 =
18 % growth rate
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Population Calculation
Example:
400 – 220 / 10 =
18 % growth rate
Population Calculation
Let’s Try.
1. Mautog City is a first-class city of Aklan. As
of yesterday, there are 5 691 people in the
city. Last year, there were 1678 new children
born and 954 people were recorded as
deceased. What is the population growth?
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Answer
• 0.13 x 100
• 13% population growth rate
Population Calculation
Let’s Try.
2. Lathegue City in Germany. As of today,
there are 269 074 population in the city. Data
shows there were 26 843 new children born
and 17 531 people died this year. What is the
population growth?
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Answer
• 0.03 x 100
• 3% population growth rate
Population Calculation
• FINDING THE DOUBLING TIME OF A POPULATION: THE RULE OF 70!!!
• (This only applies if the population is growing exponentially)
70% or 0.7) = Doubling Time (dt) in yrs
r in % r (in decimal form)
70% 0.7 = 10 years
7% 0.07
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Population Calculation Example:
Castillejos is a third-class municipality of
Zambales. As of yesterday, there are 16
760 people in the town. Last year, there
were 6 720 new children born and 3 678
people were recorded as deceased. In
how many years will the population of
Castillejos double?
Population Calculation
Example:
70% / 18% = 3.89 years
3.89 years
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Population Calculation
Example:
0.7/ .18 = 3.89 years
3.89 years
Population Calculation
Let’s Try.
Lathegue City in Germany has a total area of
568 543 sq. m. As of today, there are 269 074
population in the city. Data shows there were
26 843 new children born and 17 531 people
died this year. In how many years will the
population of Lathegue City double?
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• Population growth rate = 3%
• 70% / 3%
• 23.33 years
Population Calculation
Let’s Try.
SM Campus City has a total population of 1.75
M. Data shows there were 500 678 new
children born and 25 689 people died this
year. In how many years will the population of
SM Campus City double?
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• Population growth rate = 27%
• 70% / 27%
• 2.59 years
Population Calculation
FINDING FUTURE POPULATION FROM GROWTH
RATE:
Initial Population x (growth rate)years = Final
Population
NOTE: a growth rate of 3% is expressed as 1.03; a growth rate of
0.25% is 1.0025
468,843 people x ( 1.03 )10 years = 630,085 people
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Population Calculation
Example:
In April of 2014 the Zambales population
was 30,745,538 and it is growing by about
0.97%. Assuming a constant growth rate,
what will the population be in 2020?
Population Calculation
Solution:
30,745,538 people x ( 1.0097 )6 years =
32,578,886 people
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Population Calculation
Example:
In April of 2014 the Zambales population
was 30,745,538 and it is growing by about
0.97%. Assuming a constant growth rate,
what will the population be in 2050?
Population Calculation
Solution:
30,745,538 people x ( 1.0097 )36 years =
43,521,807 people
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Population Calculation
Example:
As of today, the Philippines has a total
population of 102 908 690 and it is
growing by about 12%. Assuming a
constant growth rate, what will the
population be in 2020, 2025, 2030 and
2050?
Population Calculation
Solution:
102 908 690 people x ( 1.12 )4 years =
161 928 816 people
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Population Calculation
Solution:
102 908 690 people x ( 1.12 )9 years =
285 373 902 people
Population Calculation
Solution:
102 908 690 people x ( 1.12 )14 years =
502 926 323 people
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Population Calculation
Solution:
102 908 690 people x ( 1.12 )34 years = 4
851 374 717 people
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Techniques to Measure Density
• Lincoln-Peterson method, relies on capturing and
marking some fraction of the total population and then
using this fraction to estimate the actual population
size
Techniques to Measure Density
3. Index of Relative Abundance – frequently relies
on indirect evidence for making comparisons of the
numbers of organisms.
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Population Dispersion
• Population Dispersion –
second fundamental
demographic characteristic
of a population; refers to the
spatial distribution of
individuals in the population
Three Types of Population Dispersion
• Clumped Dispersion – also called
aggregated dispersion, individuals may
live close together in groups in order to
facilitate mating, gain protection, or
access food resources
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Three Types of Population Dispersion
• Uniform Dispersion – also called
hyperdispersed dispersion, territoriality
and intraspecies competition for limited
resources lead to individuals living at
specific distances from one another.
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Three Types of Population Dispersion
• Random Dispersion – individuals are
spread randomly within an area or
volume.
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Age Structure
• Age Structure – the distribution of individuals
among age classes
• Life tables contain information on the age-specific
birth and death rates of individuals. From this
information, we can calculate other demographic
parameters, such as age-specific life expectancy
and the expected number of offspring produced by
each female in the population (Ro).
Age Structure
• Survivorship curve – generalized
diagram showing the number of
surviving members over time from a
measured set of births.
• Survivorship curves help to describe the
reproductive strategy of a species.
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Types of Survivorship Curves
• Type I: common among large mammals and humans; low
level of infant mortality and a population that generally will
survive until old age
• Type II: exhibited by birds, small mammals and some
reptiles; roughly equal at all ages of an organism’s life
• Type III: generally invertebrates, fish, amphibians and
plants; have a very high birth rate and also a very high
infant mortality rate.
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Sex Ratio
• Sex Ratio – ratio of males to females or
as the number of males per 100 females
Population Growth
Factors Affecting Population Growth
• Immigration – movement of individuals
into a population from another
population
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Population Growth
Factors Affecting Population Growth
• Emigration – movement of individuals
out of a population and into another
population
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Population Growth
Factors Affecting Population Growth
• Births – increase of the number of
individuals in a population
Population Growth
Factors Affecting Population Growth
• Deaths – decrease of the number of
individuals in a population
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Distinct Types of Population Growth
• Exponential Growth – occurs when a population
size increases dramatically over a period of time;
appears as J-shaped curve
• Logistic Growth – also called as sigmoid growth, a
population begins with a period of slow growth
followed by a brief period of exponential growth
before leveling off at a stable size; appears as S-
shaped curve.
The Exponential curve (also known as
a J-curve) occurs when there is no
limit to population size.
The Logistic curve (also known as an S-
curve) shows the effect of a limiting factor
(in this case the carrying capacity of the
environment).
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Carrying Capacity and Population Crash
• The carrying capacity of an environment
is the maximum number of individuals of a
particular species that the environment can
normally and consistently support.
• Population crash – dramatic decline in the
size of a population over a short period of
time.
Density-Dependent and Density-
Independent Limiting Factors
• Limiting Factor – the factor that has the greatest
effect in keeping down the size of a population
• Density-dependent Liming Factors – limiting
factors that are affected by the number of
individuals in a given area
• ex.: competition, predation, parasitism and disease
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Density-independent Liming Factors
• Density-independent Liming Factors –
aspects of the environment that limit a
population’s growth regardless of the density
of the population
• ex.: unusual weather, natural disasters,
human activities.
FLA: Zambales Population by Town (2010 Data)
• Infographic
• Source:
https://psa.gov.ph/content/population-
zambales-reached-more-half-million-
results-2010-census-population-and-
housing
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References:
• Krohne, David T. 2012. General Ecology, 2nd Edition.
Cengage Learning Asia Pte Ltd: Singapore.
• Fernandez, Elsha Vienna M. 2011. Biological Science: A
Reviewer for the Licensure Examination for Teachers.
PNU University Press : Taft Avenue, Manila.
• Melchor, Marciano B., et al. 2008. Laboratory Manual in
Biology. Rex Book Store: Manila, Philippines.
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Lakô hã salamát!Maraming salamat!
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