Tools

5. Tools — IB Biology SL Revision Notes & Topical Questions

5 min read 13 parts Lesson 1 of 10

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Lesson summary

5. Tools — IB BIOLOGY SL notes: Apply safe and ethical practice, choose measuring tools, use sensors and data loggers, and draw and analyse graphs from biological data.Hazard = a feature of a procedure that can cause harmA chemical may be an irritant to the skin.Slippery rocks on…

Risk assessment
Justified precautions
Chemicals used in biology
Hazard warning symbols
Human participants
Field work

Part 1 of 11Hazard, risk and risk assessment

Hazard

Hazard a feature of a procedure that can cause harm

A chemical may be an irritant to the skin.
Slippery rocks on a shore are a hazard.
A Bunsen burner flame can cause burns.

Risk

Risk how dangerous the hazard is, which depends on the likelihood and the severity of harm

Risk assessment

Risk assessment identifies hazards, judges the risk and changes the procedure to reduce it
In a rocky-shore quadrat study slippery rocks are a hazard and a fall is quite likely.
A fall could cause bruises or twisted ankles.
Reduce the risk by requiring shoes with good grip, avoiding rocks covered in seaweed and walking slowly.

Justified precautions

Justified precautions name the hazard and justify the precaution
Iodine is an irritant, so wear goggles and wash any skin contact immediately.

Part 2 of 11Hazard symbols

1Chemicals used in biology

Chemicals used in biology stains, enzyme-reaction reagents and chromatography solvents

2Hazard warning symbols

Hazard warning symbols nine standardised symbols in a red diamond on labels and safety data sheets

Symbol	Meaning
Health hazard	Can cause skin rashes, eye damage or harm if swallowed
Corrosive	Skin burns and permanent eye damage
Flammable	Catches fire if heated or near a flame
Acute toxicity	Life-threatening effects even in small amounts
Hazardous to the environment	Threat to aquatic life and the environment
Oxidising	Can cause fire or explosions

Part 3 of 11Ethics and environment

Ethics and environment

Animals

IB policy allows animals to be used only when there is no alternative
Experiments must not be cruel and must minimise distress.
Keep experiments short, handle animals as little as possible and release them at the end.

Human participants

Human participants they must give fully informed consent, for example when using a spirometer

Laboratory waste

Do not pour toxic waste down the sink.
Use sharps bins.
Dispose of biological waste such as bacterial plates and dissected organs correctly.

Field work

Field work avoid sensitive habitats, work in small groups and take litter away

Part 4 of 11Measuring mass and volume

1Mass

Mass a digital balance, usually to two decimal places, tared before use so the container is not included
1 kg = 1000 g.

2Volume

Volume units cm³, dm³, ml and l, with 1 ml = 1 cm³
A measuring cylinder gives approximate volumes from 10 cm³ to 1 dm³.
A volumetric pipette is the most accurate way to measure a fixed volume, usually 10 or 25 cm³, with the bottom of the meniscus on the mark.
A burette is the most accurate for variable volumes from 0 to 50 cm³ and is read from top to bottom because 0.00 is at the top.

3Gases

Gases a gas syringe, or an inverted cylinder of water if the gas is insoluble

4Time, temperature and length

Time, temperature and length a stopwatch, a thermometer or probe, and a ruler, with human reaction time affecting short times

Part 5 of 11Counting, observing and required techniques

Counting populations

Counting populations accurate counts are rare, so sampling is used
Errors arise from large populations, missed individuals, misidentification and miscounting large groups.
Cell counts use a haemocytometer or counting chamber.

Observation

Labelled biological drawings are line drawings of observed features that follow drawing conventions.
Qualitative observations such as sex, fur colour or number of limbs cannot be measured numerically.

Required techniques

Required techniques paper or thin-layer chromatography, colorimetry and serial dilutions, physical and digital molecular modelling
Light microscopy with an eyepiece graticule and preparation of temporary mounts.
Identifying and classifying organisms and random and systematic sampling.
Karyotyping and cladogram analysis.

Part 6 of 11Sensors and data loggers

Sensor

Sensor detects changes in the surroundings and converts them to electrical signals that a data logger stores
A computer then tabulates the data, calculates averages and gradients and plots graphs faster and more accurately than by hand.

pH meter

pH meter measures H⁺ concentration as a pH value, which is useful for enzyme investigations

Temperature probe

Temperature probe replaces a thermometer for experiments needing specific temperatures

Other sensors

Other sensors gas, light, heart rate and lung volume monitors, and abiotic measurements in ecology

Part 7 of 11Databases and models

Database

Database a structured collection of data, such as DNA and chromosome sequences, that can be searched, sorted and filtered

Spreadsheets

Spreadsheets they record and process data, draw graphs and perform statistical analyses

Models and simulations

Population growth curves predict real populations.
Mesocosms are model ecosystems used to test the effect of changing one variable.

Part 8 of 11Drawing graphs

Choice of graph

Choice of graph a line graph for continuous data over time and a bar chart for grouped data

Axes

Axes the independent variable goes on the x-axis and the dependent variable on the y-axis
Label both axes with units.
Choose a scale that fits all the points.

Plotting

Plotting plot points accurately in pencil so corrections are easy

Line of best fit

Line of best fit a straight line or curve that shows the trend
It passes through the majority of points with points evenly spread on both sides.
It is not a join-the-dots line.

Part 9 of 11Reading graphs

Reading graphs

Interpolation

Interpolation reading between plotted points

Extrapolation

Extrapolation extending the line beyond the points, which is less reliable

Origin

Origin decide whether (0,0) is a true data point, and if so it is a useful anchor

Intercepts

Intercepts where the line crosses an axis

Maxima and minima

Maxima and minima peaks and troughs where the gradient changes sign

Uncertainty bars

Uncertainty bars show the uncertainty or variability of each measurement

Biology-specific diagrams

Biology-specific diagrams dichotomous keys, food chains, webs and energy pyramids, and pedigree charts

Part 10 of 11Gradient and tangent

Gradient

Gradient for a straight line it is change in y divided by change in x, and it is constant

Curved graphs

Curved graphs many enzyme graphs are curves, so draw a tangent, a straight line touching the curve at one point, and find its gradient

Extrapolate the curve back to time 0.

Draw the tangent at t = 0 using a ruler.

Find the gradient as change in y divided by change in x.

State the initial rate, for example 72 cm³ in 20 s gives 72 / 20 = 3.6 cm³ s^-1.

Initial rate
- the gradient of the tangent at time 0

Part 11 of 11More from the specification

Key terms

Term	Meaning
Hazard	A feature of a procedure that can cause harm.
Risk	The likelihood and severity of harm from a hazard.
Tare	To set a balance to zero with the empty container on it.
Data logger	An electronic device that records sensor readings over time.
Tangent	A straight line touching a curve at one point whose gradient gives the rate there.
Line of best fit	A line or curve showing the trend with points evenly on both sides.
Uncertainty bar	A graph bar showing the uncertainty or variability in a value.
Interpolation	Reading values between plotted points.

Avoid these mistakes

Joining the points on a graph instead of drawing a best-fit line — draw a smooth line or straight line through the trend

Writing wear goggles with no hazard identified or justification given — name the hazard and justify the precaution

Reading a burette from the bottom up — zero is at the top

Extrapolating a trend beyond the data and treating it as a measurement — extrapolation is less reliable

Last updated: 18 October 2026