Population Growth

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Chapter 13 Population Growth
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13.1 How Populations Change
People are everywhere. Some People say that
there are too Many of us, but no one Wants to
leave.
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According to your book, There are over 6 billion
people In the world. (2000)
World Population Clock
As weve said before, many Scientists think that
this rapid Growth is a fundamental cause Of
many environmental problems.
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Usually, an organism can Produce many more
offspring Than can survive to grow up And
reproduce.
For example, a herring may lay Up to 1 000 000
eggs a year.
But each population has a Characteristic maximum
Growth rate.
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This maximum growth rate, Also known as biotic
potential, Is the rate at which a
population Would grow if every new Individual
survived to adulthood And reproduced at its
Maximum capacity.
Given the right conditions, any Population can
grow Exponentially.
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An exponential curve, or A J curve.
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The biotic potential for humans Is around 6 per
year, but For rats it is 1.5 per day, And for
bacteria it is 250 Per hour!
However, these are under the Right conditions,
there are Limits on how a population Can grow.
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As a population grows, it Consumes greater
amounts Of resources.
Eventually a resource will run Out. The resource
that limits A population from growing Is called a
limiting resource.
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Limiting resources for animals Include food,
water, shelter, And nesting sites.
For plants water, sunlight, And certain
nutrients are Limiting resources.
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When a population increases, Its individuals
compete for These limiting resources.
The combined effect of all the Factors that limit
population Size is called Environmental
resistance.
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The population eventually Ceases to grow as it
reaches, And often exceeds, its Carrying
capacity.
The carrying capacity is the Maximum population
size An environment can support For a long time.
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13.2 A Growing Human Population
The earths human population Is increasing by
about 149 People per minute, 8956 each Hour,
214934 each day, And 78 million each year!
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Human Population Growth
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Like a single ecosystem, The earth has a carrying
capacity.
The issue is that no one knows What that
carrying capacity is Because of advancements in
Technology and society.
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Throughout about 99 of our History, humans were
hunter- Gatherers.
Or people who obtain food by Hunting, fishing,
and Gathering wild plants.
Today, very few people survive That way.
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It is estimated that only about 1 million people
were on the The entire earth when humans Were
hunter-gatherers.
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Then the agricultural revolution Took care of all
that and The population grew to about 1 billion
around 1800 AD.
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Agriculture allowed people To produce more food
than they Could ever get by gathering it.
So farming increased the Carrying capacity of
the land.
So after thousands of years of Slow growth, the
population of The earth doubled by 1930.
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Then add another billion by 1960, Another in
1975, another in 1987 And yet another in 1999.
Why so fast?
Simple, people were living longer Because of
sanitation, Nutrition, and medicine.
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Although it seems that there Is an explosion (and
there is In certain places), in
industrial countries, it has slowed.
This is because birth rates have Slowed since
there is no need for extra kids to work the
farms.
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There is a theory to support this
It is the theory of demographic Transition by
Frank Notestein.
This states that the economic And social progress
of the Industrial revolution affects Population
growth in 3 stages.
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• Both birth and death rates
• Are high in preindustrial
• Societies, and the population
• Grows slowly, if at all.

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2. When health care improves, The population size
increases.
The birth rate stays high, and People are living
longer, so The population grows by 3 Each year.
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3. Birth rates fall until they are Roughly equal
to death rates, And population growth Slows and
stops.
Why do birth rates fall?
Women usually get a better Education, and
parents see kids Not as workers, but as a huge
Financial responsibility.
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Stages of Demographic Transition
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Some countries are still In the second stage.
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Population pyramids
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13.3 Problems
The Death Clock When Am I Going To Die?
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The united nations and the World bank have
determined That fuel wood is a Limiting resource
in many Developing countries.
Without the ability to have a Fire to cook their
food, Many people suffer from Malnutrition or
even starvation.
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Each year about 10 million people Die of diseases
contracted From dirty water.
People in industrialized Countries feel safe
drinking Water from the tap, However many people
in Underdeveloped countries Die from parasites
by drinking Unboiled water!
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As a countrys population grows, More and more
people move Toward The cities searching for
work.
The united nations projects that Up to ¼ of the
worlds Population will be homeless By 2020.
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Environmental refugees are People who are driven
from Their homes by severe Environmental damage.
The millions of people who left Their homes in
Kenya, Somalia, And Ethiopia in search of Food
are also environmental Refugees.
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Slowing the growth of the Human population is
considered Vital to future peace and Prosperity
throughout the world.
In order to be rich SEE THE SIGN ON THE WALL!
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Developed countries contain Only 21 of the
worlds Population, but they consume 75 Of its
energy, produce 70 of The global CO2, and 90 Of
the global hazardous waste.
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To achieve a sustainable future, The problems of
overpopulation And overconsumption must be
Solved.
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THE END