demography and population growth - …...demography and population growth by danilo villar rogayan...

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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


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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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• Population Density, the number of

individuals per unit area.


• 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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• Age Structure,

configuration of the

age of the

individuals in a

population


• Demography – the quantitative description of

a population

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• 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


• 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.


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.


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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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?


Example:

6 720 / 16 760 = 0.40

40 % birth rate

400 crude birth rate

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Example:

3 678 / 16 760 = 0.22

22 % death rate

220 crude death rate


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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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


• 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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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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Example:

400 – 220 / 10 =

18 % growth rate


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


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


• 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?


Example:

70% / 18% = 3.89 years

3.89 years

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Example:

0.7/ .18 = 3.89 years

3.89 years


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


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


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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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?


Solution:

30,745,538 people x ( 1.0097 )6 years =

32,578,886 people

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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?


Solution:

30,745,538 people x ( 1.0097 )36 years =

43,521,807 people

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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?


Solution:

102 908 690 people x ( 1.12 )4 years =

161 928 816 people

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Solution:

102 908 690 people x ( 1.12 )9 years =

285 373 902 people


Solution:

102 908 690 people x ( 1.12 )14 years =

502 926 323 people

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Solution:

102 908 690 people x ( 1.12 )34 years = 4

851 374 717 people

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• 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


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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• 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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• 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


• Emigration – movement of individuals

out of a population and into another

population

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Population Growth


• Births – increase of the number of

individuals in a population

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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