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Collect Process DiscussPlan
WorldPopulation
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Collect Process DiscussPlan
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
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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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Lets use a computer model to see what happens as the bacteria multiply over time.
World Population
When each bacterium has had enough nutrients it divides in two.
If it does not manage to take in enough nutrients it dies.
Time Number minutes
0 1 20 3 40 6 60 10 80 19100 38120 66140 89160 104180 131200 157220 180240 183260 181
Task : Can you plot the population number against time?
Time
Number
Nutrients
Bacterium
Deadspace
Bacterial growth
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Your graph should look something like this.
Chart showing population of bacteria against time
300
What do you think will happen to the bacteria next?
350
?
Data plotted
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What is happening during the ‘stationary’ phase?Hint: as quickly as new bacteria are appearing…
Scientists have discovered from growing different cultures of bacteria that they follow the same pattern:
The chart is often broken up into four phases.
Time
Number
Lag
Log
Stationary
Death
Four phases
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World Population
Time
Number
Do you think that the human population grows in the same way as the bacteria?
Time
Number
Perhaps the World’s Population will move into the death phase?
2006?
2006?
2006?
Is it still racing up or has it levelled off?Human growth curve
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World Population
We can think of each country (or continent) as a separate petri dish (of different sizes).
Collecting data for the whole world is difficult.
Are there parts of the world that have increasing populations, others which are steady and others in decline?
Countries as dishes
Something you believe might be true is called a hypothesis. For example
“I believe Mexico has a steady population.”
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Which parts of world do you think might have
• an increasing population?
• a steady population?
• a declining population?
Something you believe might be true is called a hypothesis.
To help investigate a hypothesis, we can use the Problem Solving Approach…
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World Population
Making hypotheses
Time
Number
steady
incr
easi
ng
declin
ing
First we decide what problem to
solve and what
First we decide what problem to
solve and what data we need
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Then we collect suitable data.
Then we examine our data and make it easier to understand.
We report back what we found – and compare it to what we expected.
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World Population
PSA cycle
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World Population
Important: It doesn’t matter if your hypothesis is wrong, because you’ll always learn something new from the data!
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….”
Your hypothesis
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How far back in time should/can we go?
What information do we need to collect?
World Population
Types of data
What data to collect?
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The Problem Solving Approach
You are now here.
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A number of websites contain information on population sizes.
prb.org
census.gov
wikipedia.org unfpa.org
It is difficult to find the world’s actual population; we use estimates based on national censuses and calculations using birth and death rates.
Suitable sources
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World Population
www.rsscse.org.uk/qca/population
First choose“Total Population”
Then selecta country
Choose the years you want to use.
(1950 onwards)
A webpage will appear with your
selected data.
US census
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World Population
www.rsscse.org.uk/qca/population
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
You arenow here.
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World PopulationNow that we have collected some data, what can we do to make it easier to understand?
We will plot time on the x-axis
We will plot population on the y-axis
We can draw a line graph of the data
Plotting data
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World Population
Mexico
0.00
20.00
40.00
60.00
80.00
100.00
120.00
1950 1960 1970 1980 1990 2000 2010 2020 Year
Mil
lion
s o
f p
eop
le
+10+14
+16
+16
+15
+13 predictedHow would you
describe the growth of this country since
1950?Lets see how the population has grown every 10
years.
By how much will it grow between
2000 and 2010?
Looking at growth
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The Problem Solving Approach
You arenow here.
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Describe the growth curve for your chosen population.
Where do you think the country is on the growth curve?
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
Time
Number
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The Problem Solving Approach
You arenowhere.
You can build on your investigation by continuing here...
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How fast is the population growing in your country compared to
• neighbouring countries?
• richer or poorer countries?
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You may like to continue your investigation by considering household size in the UK or population pyramids in different countries:
Some additional investigations:
Population pyramids
Household numbers
Number of womenSize of family
Extending the work
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Household sizes
What does it show?Describe the pattern that you can see.What impact could decreasing household size have?What other factors relating to household size could you investigate?
As populations grow, space and available housing becomes important. Consider at the graph below:
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Household sizes
The graph below shows the change in household size since 1971.Can you create a similar graph for your class?What is the mean household size in your class?How do you compare to the national picture?
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