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POPULATION
DISTRIBUTION,
GROWTH AND
DENSITY
POPULATION
¡ Refers to a group of organisms of the
same kind or species living in the same
place at the same time
¡ A population may increase or decrease
due to birth, death, immigration and
migration
Daile M eek S. M em breve
Biology Departm ent, College of science
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POPULATION GROWTH
POPULATION CHARACTERISTICS
¡ Is the change in a population over time, and can be
quantified as the change in the number of individuals of any
species in a population using ‘per unit time’ for measurement
¡ In demographics, population growth rate (PGR) is the rate at
which the number of individuals in a population increases in
a given time period as a fraction of the initial population.
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Natality
Mortality
Sex ratio
Age
distribution
Growth
rates
Special
distribution
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NATALITY OR BIRTH RATE
MORTALITY OR DEATH RATE
¡ Refers
¡ The number of deaths per year.
to the number of
individuals added to the
population through reproduction.
¡ It is usually discussed in terms of the number of individuals who die
per one thousand individuals in the population per year
¡ It is the number of individuals
born
per
one
thousand
individuals in the population per
year.
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POPULATION AGE DISTRIBUTION
POPULATION CHARACTERISTICS
¡ The individuals of different age groups in a population.
¡ Age distribution
¡ Models that incorporate age structure allow better prediction of population growth, plus
the ability to associate this growth with the level of economic development in a region.
¡ Population growth rate
¡ Bodenhelmer (1938) recognizes three ecological ages as:
¡ Population density
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¡
Pre-reproductive
Reproductive
¡
Post reproductive
¡
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https://image.slideserve.com/228323/population-pyramids-for-the-four-demographic-transitionphases-l.jpg
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https://cdn.thinglink.me/api/image/786025515705171970/1240/10/scaletowidth
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POPULATION GROWTH CURVE
¡ Biotic potential is biological ability to produce
offspring
¡ Sex ratios and age distribution directly affect the
rate of reproduction within a population.
Population | Department of Health website (doh.gov.ph)
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TYPICAL POPULATION GROWTH CURVE
TYPICAL POPULATION GROWTH CURVE
¡ Deceleration phase
¡ occurs when the population growth rate begins to
slow.
¡ Lag
phase is the period of time
immediately following the establishment
of a population, when the population
remains small and fairly constant
¡ The number entering the population by
reproduction remains high but the number leaving
by death increases and the population growth rate
begins to slow
¡ Stable Equilibrium Phase
¡ Exponential growth phase: period of time
when a population is growing rapidly
¡
¡ Period of time when a population stops growing
and maintains itself at a reasonably stable level
Birth rate > death rate
¡ Birth rate ~death rate
The Population Growth Curve - Population Ecology - EVOLUTION AND ECOLOGY - CONCEPTS IN BIOLOGY (schoolbag.info)
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The Population Growth Curve - Population Ecology - EVOLUTION AND ECOLOGY - CONCEPTS IN BIOLOGY (schoolbag.info)
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CARRYING CAPACITY
POPULATION GROWTH LIMITING FACTORS
¡ The number of individuals of a species that can survive in that area
¡ Density-dependent
over time
¡ Linked to population size
¡ Four broad categories of factors that determine the carrying capacity
¡ Diseases
for a population
¡ Lack of food
1. Availability of raw materials
¡ Density-independent
2. Availability of energy
3. Accumulation of waste products and mean of disposal
¡ Droughts, floods, habitat destruction
4. Interactions among organisms
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POPULATION
DENSITY
•
Is the number of individuals
per unit area
•
High population density
needs more resources
(competition)
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FACTORS THAT INFLUENCE HUMAN POPULATION GROWTH
ECOLOGICAL
FOOTPRINT
•
The impact of a person or
community
on
the
environment, expressed as
the amount of land required
to sustain their use of
natural resources
•
Calculates the amount of
land and water we need to
provide everything we use in
life
•
To
be
ecologically
sustainable, each person should
consum e no m ore than 1.8 ha of
land
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SOCIAL FACTORS
¡ Religious
¡ Cultural
¡ Women education
ECONOMICS FACTORS
¡ In
less developed countries, the
economic benefits of children are
extremely important
¡ In
the developed world, large
numbers of children are an
economic drain
https://i.pinimg.com/736x/95/7a/de/957adeffa95e9a0d87940214d86fb793--sustainable-tourism-carbon-footprint.jpg
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FACTORS THAT INFLUENCE HUMAN POPULATION GROWTH
FAMILY PLANNING
POLITICAL FACTORS
¡ Governments can reward or punish high fertility rates:
¡ China’s one-child policy decreased the country’s fertility rate
paid maternity, child tax deduction
from 6 to 1.8 in two decades (very controversial).
¡ Policies to encourage more children (low birth rate
country)
¡ Family planning strategies
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