Problem Solving�Higher Biology

• Percentages
• Percentage Change
• Averages
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• Selecting Statement
• Ratios
• Population Calculations
• Drawing a Graph
• Describing Relationships
• Selecting Information
• Making Predictions
• Describing Trends

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• Two Scale Graphs
• Variables
• Controls
• Reliability
• Validity
• Accuracy
• Conclusions
• Converting to %
• Error Bars

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1. Percentages

ATTEMPT THIS QUESTION�

Calculate the percentage number of deaths for each year

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• 45÷1070 x 100= 4.21
• 12÷420 x 100= 2.86
• 60÷1960 x 100= 3.06
• 90÷2290 x 100= 3.93

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Answer A

ATTEMPT THIS QUESTION

60% of 155= 60/100 x 155=93

93

2. Percentage change

ATTEMPT THIS QUESTION

Use DOOTH (Difference Over Original Times a Hundred) to calculate a percentage decrease

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Men in England

• 603-324= 279

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• 279/603 x 100= 46.3%

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Woman in England

• 402-221= 181

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• 181/402 x 100= 45.0%

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Men in Scotland

• 684-396= 288

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• 288/684 x 100=42.1%

Woman in Scotland

• 476-275= 201

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• 201/476 x 100= 42.2%

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Men in England

ATTEMPT THIS QUESTION

Use DOOTH

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870-200= 670

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670/200 x 100= 335

Answer C

3. Averages

Calculating an Average:

An average is the result that you get when you add two or more numbers together and divide the total by the number of numbers you added together.

• Add (total) all of the numbers in the set you want to average.
• Count how many individual values( groups) are in the set of numbers.
• Divide step 1 by step 2 (Divide the total by the number of groups.)

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ATTEMPT THIS QUESTION

Increase in number of species is 14 over 2.8 million years

To get it per million years you must divide 14 by 2.8= 5

5

ATTEMPT THIS QUESTION

For 2.5g of food 42 times entering torpor per week

= 42/7 per day =6

Average time spent = 120 x 6 = 720.

720

4. General Calculations

How many times greater is 400 compared to 50.

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Simply divide the larger number by the smaller

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400 ÷ 50= 8

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400 is 8 times bigger that 50.

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3.2 x 10⁹ ÷ 4.0 x 10⁶ = 800

800

Calculations

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Calculations

1mg per kg

= 0.1mg per 100g (divide both by 10)

=0.01mg per 10g (divide both by 10)

=0.02mg per 20g (times both by 2)

Given the drug twice a day 0.02mg x 2 = 0.04 mg per day

For 15 days 0.04 x 15= 0.6mg Answer D

5. Selecting the correct statement

• You will be given 4 statements – work through each one to decide if they are true or false
• You may have to do calculations for each statement
• There will only be one right answer!

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Answer D

Add up total costs, early + late!

Answer C

Answer C

6. Ratios

Hints

• What you do to one number you must do to the other(s)
• You can only multiply or divide
• Find the highest factor that divides into both values
• Try dividing all numbers by the highest number first eg 250:50, try 250/50 = 5

50/50 = 1

so 5:1

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ATTEMPT THIS QUESTION

324: 396 divide both by 36

9: 11

9

11

9: 15: 90 divide all by 3

3: 5: 30

3

5

30

19:2

38:4

7. Calculations involving populations

ATTEMPT THIS QUESTION

Step 1- select correct value from graph 1.

400 / 100 000

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Step 2-select the population size

From graph 2.

3 000 000.

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Step 3- calculate how many 100 000 are in 3 000 000

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3 000 000 ÷ 100 000 = 30.

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Step 4 – times 400 by 30= 12000.

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Answer C

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8. Drawing a graph

1) Draw axes clearly with a ruler

2) Label axes including the quantity involved (e.g: mass, distance, time) AND include units (e.g: kg, m, s).

3) Use an appropriate and even scale.

4) Fill over 50% of the graph paper.

5) Plot points on the graph using small and neat points.

6) Join plotted points with a ruler.

8. Drawing a graph

BUT…How do I know when to use a bar graph or a line graph?

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Bar graphs should be used with discrete data e.g. groups or categories such as hair colour or eye colour

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Line graphs should be used with continuous data – a range of numbers e.g. time in minutes

9. Drawing a graph

ATTEMPT THIS QUESTION

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10. Using data to describe relationships from a graph /table

Question: Use values from the graph/table to describe .. The relationship between two variables ~ 1/2 marks (usually 2!)

• To access the marks you must get the ‘cause and effect’ correct.
• In biology the variable on the X axis always influences the variable of the Y axis.
• Graphs/Data in 2 mark Qs will generally have one/two ‘changing points’ where there is a noticeable change in the data – these are important and values should be included in your answer!
• Need to include the names and the units of both variables at least once to access all marks.

Things to think about …..

• Which parts of the table are you looking at?
• Which variable is the cause? The effect?
• Where is the ‘changing point’?
• What happens up to this point?
• What happens after this point?

Answer:

ATTEMPT THIS QUESTION

Answer:

Things to think about …..

• Which Y axis are you looking at? Are you using all of the X axis?
• Where is the ‘changing point (s)’?
• What happens up to this point?
• What happens after this point?

Answer:

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Answer:

HH2019

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Answers

H2019

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11. Selecting from a graph / table

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Regular:

830 -780 = 50

HIIT:

820 – 740 = 80

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Difference =

80 -50 = 30s

Answer A

4.5

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Death rate 80-89 = 12 per 100,000

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Death rate 90-99 = 7.5

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12-7.5 =

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ATTEMPT THIS QUESTION

35% of 1000

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35÷100 x 1000 = 350.

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ATTEMPT THIS QUESTION

Birth rate with donor eggs at age 38 is 54% from table

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Birth rate with own eggs at age 38 is 18% from graph

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54 -18 = 36.

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ATTEMPT THIS QUESTION

At 60 mins glucose concentration is 250mg per 100cm³

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5 litres of blood contains 5000cm³

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Calculate how many 100 cm³ are in 5000.

5000 ÷100 = 50 cm³

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250mg x 50 = 12,500mg

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ATTEMPT THIS QUESTION

Fruit fly- percentage of genome is 18%

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18÷100 x 1.4 x10 = 2.52 x 10⁷ or 25, 200 000

12. Making predictions from �a graph / table

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Read from left hand scale and blood glucose line.

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Blood glucose dropped from 250 mg/100cm³ to 205 mg/100 cm³ in 90 mins

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So it dropped 45 mg/100 cm³ in 90mins.

Thus it takes (90/45 = 2) = 2 mins to drop 1 mg/100 cm³

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To return to normal 145 mg/100 cm^3, blood glucose concentartions must drop (205-145) another 60 mg/100 cm³ .

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It will take 60 x 2 to get back to normal + 120 mins.

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Add decrease in yield % for weeds and insects for all crops.

D is largest.

Answer D

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An increase 0.6 x 10⁶ causes and increase in proteins of 300

This is an increase of 50 (300 / 6) per 0.1 x 10⁶ which equals an increase of 50 x 4 per per 0.4 x 10⁶ = 200

3900+200= 4100

4100

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Decrease in pH of 0.8 every 2 days, so at 10 days 4.2 - 0.8 = 3.4

pH 3.4

13. Describing trends from a graph/�making conclusions from data

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Answer:

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✓

✓

✓

×

×

×

Answer = A

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14. Interpreting data on a two scale graph

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300

1.

2.

3.

300

Answer = B

C

Answer = 37.2

Experimental design

15. Variables

The independent variable

This is the variable that the experimenter would deliberately change.

The dependent variable

This is the thing that is measured at the end of the investigation.

The controlled variables

This is any other variable that could effect the measured variable and must be controlled to ensure it stays the same.

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Question:�Identifying control variables …

• If asked to state variables to be kept constant, you must include variables that are not already mentioned in the stem of the question.
• This is the variables that must be controlled to keep the experiment valid (fair)
• Think pH, concentration, volume, time, gender, age etc.
• Careful reading = maximum marks

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Answer:

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Answer = C

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16. Control experiment�

Question:�Control experiments…

• A control experiment is an identical ‘dummy’ experiment set up with one exception: the factor causing the result is missing.
• You can be asked:
• To suggest a control

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• State the purpose of including a control

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Basic answer structure:

• Set up identical apparatus except use X instead of Y.

Basic answer structure:

• To prove that ‘independent variable’ was causing …..

• Control experiments use identical apparatus but substitute the key chemical for an equal volume/mass of something else:

Question:�Control experiments…

Set up identical apparatus but use an equal volume of boiled catalase solution instead of active catalase

To show the change in dependent variable is due to the change in the independent variable.

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To show the increase in heart rate is due to the effect of the hormone.

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To allow comparison with the fleas with the hormone

ATTEMPT THIS QUESTION

17. Reliability�

Question:�Reliability…

You can be asked this one of two ways:

• How would you increase reliability?
• You must state precisely what you would do – e.g. repeat the experiment at each pH
• E.g. ‘repeat the experiment and calculate an average’

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2. Describe how the design of the experiment ensured reliability.

• READ the information available to you – the answer is in there!
• E.g. They had 5 samples at each pH instead of just one.

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Answer:

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18. Validity

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To be valid both the treatment group and placebo group must have the same balance of the females smokers, female non smokers, males smokers and male non smokers.

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so Answer = B

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Answer = D

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19. Accuracy

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21. Conclusion

Question:�Drawing conclusions…

• You must first READ the stem of the questions and identify what the investigation was aiming to find out.

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• Secondly, READ the data given (graphs, tables etc)

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• You must correctly identify the cause and effect

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• Most conclusions are one sentence long.

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• Ensure your conclusion relates to the dependent variable and not the measured variable.

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ATTEMPT THIS QUESTION

Answer:

A protein supplement is used by some people who take part in sport. They

believe its use increases muscle mass and therefore improves performance in

sporting activities such as weightlifting.

An investigation was carried out to test if protein supplements improved the

ability of the upper leg muscles to raise weights.

ATTEMPT THIS QUESTION

ATTEMPT THIS QUESTION

22. Explaining data expressed as /1000�or as a percentage

Question:�Converting data into percentages….

• Experiments that compare data from different groups of individuals rarely have the same number of participants.
• To allow data to be compare it is often converted into percentages.

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• You can be asked why the data has been converted into percentages…

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Basic answer structure:

• Because each of the groups/experiments had different numbers of participants/starting values.

Question:�why is data expressed as per 1000….

• Experiments that compare data from different populations of individuals rarely have the same number of participants.
• To allow data to be compare it is often expressed as a value / 1000

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• You can be asked why the data is expressed as /1000

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Basic answer structure:

• Because each of the groups had different population numbers.

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23. Error bars

The error bars on a graph show several things:

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• The variability of the data (large error bars means the data is more variable).

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Data bar “e” has the largest error bars so is more variable than

data set “b” which has the smallest error bars so is the least

variable

The error bars on a graph show several things:

2. The statistical significance

The data is not significantly different as the error bars overlap

The data is significantly different as the error bars do not overlap

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The end