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Plan
Collect
Process
Discuss
World
Population
Title slide
Plan
Collect
Process
Discuss
World Population
Every second the number of
people in the world grows.
How many people do you think
there are in the world right now?
How many babies do you think
will be born during this lesson?
Online population clock
Population clock
Plan
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Discuss
World Population
If the population is increasing,
will we ever run out of space?
If so, when might it happen?
What is the maximum number of
people the world can support?
To help answer this scientists have studied the way bacteria
grow on a petri-dish filled with nutrients.
They start with a few bacteria and give them lots of food
(nutrients) and space in which to multiply.
Petri dish model
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World Population
Discuss
Time Number
minutes
Nutrients
Dead
space
Bacterium
Number
When each bacterium
0
1has had
20 it divides
3
enough nutrients
in two.
40
6
60
10
If it does not manage
to take in
80
19
enough nutrients
100 it dies.
38
120
66
Lets use a computer
model
to
140
89
160
see what happens
as104
the bacteria
multiply over 180
time. 131
200
157
220
180
240
183
260
181
Time
Task : Can you plot the population number against
time?
Bacterial growth
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World Population
Your graph should look something like this.
Chart showing population of bacteria against time
?
300
350
What do you think will happen to the bacteria next?
Data plotted
Plan
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World Population
Scientists have discovered from
growing different cultures of
bacteria that they follow the
same pattern:
Number
Stationary
Log
Lag
Death
Time
The chart is often broken up into four phases.
What is happening during the ‘stationary’ phase?
Hint: as quickly as new bacteria are appearing…
Four phases
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World Population
Do you think that the human population grows in the same way
as the bacteria?
Number
Time
Number
2006?
2006?
2006?
Time
Perhaps the World’s Population will move into the death phase?
Is it still racing up or has it levelled off?
Human growth curve
Plan
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Discuss
World Population
Collecting data for the whole world is difficult.
We can think of each country (or continent) as a separate petri
dish (of different sizes).
Are there parts of the world that have increasing
populations, others which are steady and others in decline?
Countries as dishes
Plan
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World Population
Number
Discuss
steady
Which parts of world do you think might
have
• an increasing population?
Time
• a steady population?
• a declining population?
Something you believe might be true is called a hypothesis.
For example
“I believe Mexico has a steady population.”
To help investigate a hypothesis, we can use the
Problem Solving Approach…
Making hypotheses
Plan
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World Population
We report back what
we found – and
compare it to what
we expected.
Plan
Discuss
Then we examine
our data and make it
easier to understand.
Discuss
First we decide
what problem to
solve and what
data we need
Collect
Process
Then we collect
suitable data.
PSA cycle
Plan
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Process
Discuss
World Population
Which part of world are you going to consider?
What do you think is happening to the population there?
What might be causing the population to grow like that?
Write your ideas down, see if you can
form them into a hypothesis.
“I think that….because….”
Important: It doesn’t matter if your hypothesis is wrong,
because you’ll always learn something new from the data!
Your hypothesis
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World Population
What information do we need to collect?
How far back in time should/can we go?
Types of data
What data to collect?
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Discuss
The Problem Solving Approach
Plan
Discuss
You are
now here.
Collect
Process
PSA cycle
Plan
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World Population
It is difficult to find the world’s actual population; we use
estimates based on national censuses and calculations using
birth and death rates.
A number of websites contain information on population sizes.
census.gov
prb.org
wikipedia.org
unfpa.org
Suitable sources
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World Population
www.rsscse.org.uk/qca/population
Discuss
A webpage will
appear with your
selected data.
First choose
“Total Population”
Then select
a country
Choose the years
you want to use.
(1950 onwards)
US census
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World Population
www.rsscse.org.uk/qca/population
Discuss
A webpage will
appear with your
selected data.
If you want to use this data as a spreadsheet
(to use in Excel) then click on File  Save As.
Then rename the file to population.CSV
Creating a CSV
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The Problem Solving Approach
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Discuss
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You are
now here.
PSA cycle
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World Population
Now that we have collected some data, what
can we do to make it easier to understand?
We can draw a line graph of the data
We will plot population on the y-axis
We will plot time on the x-axis
Plotting data
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Millions of people
World Population
+13
120.00
predicted
100.00
+15
80.00
+16
40.00
Lets see how the
population has
grown every 10
years.
+16
60.00
+14
+10
Mexico
20.00
0.00
1950
1960
1970
1980
How would you
describe the growth
of this country
since 1950?
1990
2000
2010
2020
Year
By how much will it
grow between
2000 and 2010?
Looking at growth
Plan
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The Problem Solving Approach
Plan
Discuss
You are
now here.
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PSA cycle
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World Population
Discussion
Describe the growth curve for your chosen population.
Where do you think the country is on the growth curve?
Number
Time
What do you think will happen to this country over the next
• 10 years (decade)?
• 100 years (century)?
Could you work out the maximum population your country is
likely to reach?
Discussing findings
Plan
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The Problem Solving Approach
You can build on
your investigation by
continuing here...
Plan
You are
now
here.
Discuss
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PSA cycle
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World Population
Discussion
Some additional investigations:
How fast is the population growing in your country compared to
• neighbouring countries?
• richer or poorer countries?
You may like to continue your investigation by considering
household size in the UK or population pyramids in different
countries:
Household
numbers
Population
pyramids
Size of family
Number of women
Extending the work
Plan
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World Population
Discussion
As populations
What
impact
could
grow,
decreasing
space andhousehold
available size
housing
have?
does it show?
What
becomes
other
important.
factors
relating
Consider
to at
household
the
graph
size
below:
could you
Describe
the
pattern
that you
can
see.
investigate?
Household sizes
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World Population
Discussion
Can graph
The
you create
belowa shows
similarthe
graph
change
for your
in household
class?
size since
1971. is the mean household size in your class?
What
How do youHousehold
compare tosizes
the national
picture?
sizes
in
the
UK
Household
in
the
UK
Household
sizes
in
the
UK
Household sizes in the UK
Household
sizes
in
the
UK
Household
sizes
in
the
UK
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in
the
UK
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sizes
in
the
UK
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sizes
in
the
UK
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sizes
in
the
UK
Household
sizes
in
the
UK
Household sizes
sizes in
in the
the UK
UK
Household
100%
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100%
Percentage
Percentage
Percentage
Percentage
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Percentage
Percentage
Percentage
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Percentage
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Key
100%
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6+
80%
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6 6++6 +
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80%
5
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80%
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6 5+
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6
60%
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60%
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555455 5 5
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3444 4 4
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3
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22
20%
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2
1
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20%
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20%
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111 1 1
20%
11
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Household sizes
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