General Bio Knowledge & Science Skills for Exams

Question 1

e.g. if coloured juice leaks out of a frozen fruit, what word would you use to describe the colour?

Answer 1

pigment

Question 2

By changing the temperature, a student concludes that yeast cells are killed between 50°C and 70°C. Suggest one way that the student can improve the accuracy of the experiment.

Answer 2

Repeat experiment with smaller temperature intervals between 50°C and 70°C.

Question 3

By changing the temperature, a student concludes that yeast cells are killed between 50°C and 70°C. Suggest one way that the student can improve the reliability of the experiment.

Answer 3

• Repeat the experiment four more times at each temperature.
• Ignore any anomalous results.

Reliablility = repeats

Question 4

Explain why repeats are important.

Answer 4

Anomalies can be ignored so the mean is more reliable.

Question 5

You have drawn a graph of the absorption of red light (from 0.25 a.u. to 1 a.u.) against the percentage of glucose concentration. An unknown solution has an absorption of 0.19 a.u. of red light. How can you estimate the glucose concentration of the unknown solution?

Answer 5

You can’t as you can’t extrapolate data.

Question 6

You measured the glucose concentration at 0.06%, 0.13%, 0.25% and 0.50%. Where does your line of best fit end?

Answer 6

Ends at your first data point to the last one - you can’t extrapolate your line of best fit. This means it never reaches the y-axis (never goes beyond 0.06% glucose concentration).

Question 7

What lines do you need to draw for a table?

Answer 7

Pencil lines between the columns and rows & box it - you must draw a box around the whole table.

Question 8

unit M = ?

Answer 8

mol/dm³ or
moldm^-3

Question 9

unit mol/dm³ or
moldm^-3 = ?

Answer 9

M

Question 10

negative control

Answer 10

A control test that isn’t expected to have any effect on the experiment, used to check that only the independent variable is affecting the dependent variable (and not any other external factors). They do not have the reagents/treatments that is expected to have an effect

Question 11

negative control example

Answer 11

• Not giving a group of people the treatment (e.g. antibiotic) that might have an effect
• Not adding an enzyme when investigating enzyme activity

Question 12

positive control

Answer 12

A control which shows what positive results look like, to check that it is possible with the current setup

Question 13

positive control example

Answer 13

Known treatment/reagent/material that works

Question 14

difference between a reading and a measurement

Answer 14

Reading = judgement of 1 value
Measurement = judgement of 2 values, difference of these values is recorded

Question 15

uncertainty and margin of error for a 10cm³ syringe with increments of 1cm³

Answer 15

Uncertainty = +- half of resolution = =- 0.5cm³
Margin of error = resolution or twice the uncertainty = 1cm³

Question 16

How can you minimise the uncertainty in data?

Answer 16

• Use equipment with a greater resolution
• Use a larger sample size
• Measure a greater quantity (the uncertainty of the measuring equipment stays the same but the reading increases, decreasing the percentage uncertainty)

Question 17

greater/higher resolution

Answer 17

apparatus with a greater resolution have smaller increments (e.g. 0.01g rather than 0.1g) so can measure a quantity more finely

Question 18

valid data

Answer 18

Data that can answer the original question (it’s precise & accurate). All other variables must have been controlled

Question 19

reliable

Answer 19

A measure of how repeatable an experiment is, so that it gets the same results. Reliability encompasses accuracy and precision

Question 20

What causes a lack of precision?

Answer 20

Random error

Question 21

What causes a lack of accuracy?

Answer 21

Random and systematic errors

Question 22

How can you increase precision?

Answer 22

Reducing the effect of random errors e.g.
* Use equipment with a greater resolution
* Allow things to acclimatise (e.g. letting something sit in a water bath for a constant but long enough time)

Question 23

How can you increase accuracy?

Answer 23

• Use quantitative data rather than qualitative data (more accurate methods)
• Repeat the measurements at least three times (minimum) to discount anomalies and calculate the mean

Question 24

How can you increase validity?

Answer 24

• Keep control variables constant throughout the experiment
• Repeat the measurements at least three times (minimum) to discount anomalies
• Use more intermediate values so the trend can be identified more clearly

Question 25

How can you increase reliability?

Answer 25

• Keep control variables constant throughout the experiment
• Repeat the measurements at least three times (minimum) to discount anomalies

Question 26

How does repeating an experiment at least twice improve the investigation? [2 marks but 3 points]

Answer 26

improves reliability (accuracy not credited?)
assess the variability / spread of results (or calculate the standard deviation)
allows calculation of (more accurate) mean

Question 27

impervious

Answer 27

not allowing fluid to pass through

Question 28

structural diagram

Answer 28

The diagram showing the elements and bonds between them in a molecule

structural formula