Review and Assessment Preparation » Practical Skills Review

What you'll learn this session

Study time: 30 minutes

Essential laboratory safety rules and procedures
How to use common laboratory equipment correctly
Techniques for accurate measurements and observations
Methods for recording and analyzing experimental data
Skills for planning and conducting biological investigations
How to evaluate experimental procedures and results

Introduction to Practical Skills in Biology

Practical work is a vital part of biology. It helps you understand scientific concepts, develop important skills and learn how scientists work in the real world. In your IGCSE Biology exams, you'll be tested on your practical skills even if you don't do a practical exam!

Key Definitions:

Variable: A factor that can change during an experiment.
Control variable: A factor kept the same to ensure a fair test.
Independent variable: The factor you deliberately change.
Dependent variable: The factor you measure as a result.
Accuracy: How close a measurement is to the true value.
Precision: How close repeated measurements are to each other.

⚠ Laboratory Safety

Always follow these essential safety rules:

Wear safety goggles when handling chemicals
Tie back long hair and secure loose clothing
Never eat or drink in the laboratory
Know the location of safety equipment (fire extinguisher, eye wash, etc.)
Report all accidents immediately
Wash hands before leaving the lab

🔬 Common Equipment

You should be familiar with using:

Microscopes (light and dissecting)
Measuring cylinders and beakers
Pipettes and burettes
Thermometers and pH meters/paper
Bunsen burners and water baths
Stopwatches and rulers

Planning Investigations

A good biological investigation follows a logical sequence and addresses a clear scientific question. The planning stage is crucial for success.

Steps in Planning an Investigation

🤔 Ask a Question

Start with a clear, testable scientific question. For example: "How does light intensity affect the rate of photosynthesis in pondweed?"

💡 Form a Hypothesis

Make a prediction based on your scientific knowledge. For example: "Increasing light intensity will increase the rate of photosynthesis until a limiting factor prevents further increase."

📝 Plan Method

Design a step-by-step procedure that controls variables and collects reliable data. Consider equipment needed, safety precautions and how to record results.

Making Accurate Measurements

The quality of your results depends on how well you measure and observe. Here are key techniques for common measurements in biology:

📊 Volume Measurements

Read liquid levels at eye level
Look at the bottom of the meniscus
Use appropriate equipment for the volume needed:
- Beakers: rough measurements
- Measuring cylinders: medium accuracy
- Pipettes/burettes: high accuracy
Record to the appropriate number of decimal places

🌡 Temperature Measurements

Ensure thermometer bulb is fully immersed in the substance
Don't let the bulb touch the sides of the container
Allow time for the reading to stabilize
Read at eye level
Record to the nearest 0.5°C for standard thermometers
Digital thermometers may offer greater precision

Microscopy Skills

The microscope is one of the most important tools in biology. Knowing how to use it properly is essential.

Preparing a Microscope Slide

Place a small sample of the specimen in the center of a clean slide
Add a drop of water if needed (for wet mounts)
Lower a coverslip at an angle to avoid trapping air bubbles
Blot excess water with filter paper
For staining: add a drop of stain before the coverslip, or add stain at the edge of the coverslip and draw it under using filter paper

Using a Light Microscope

Follow these steps for successful microscope use:

Start with the lowest power objective lens
Place slide on stage and secure with clips
Use coarse adjustment to focus while looking from the side
Look through eyepiece and fine-tune focus with fine adjustment
Adjust light using diaphragm/light intensity control
Once focused, you can switch to higher power objectives
Remember to refocus using ONLY the fine adjustment when changing magnification

Calculating Magnification: Total magnification = Eyepiece lens magnification × Objective lens magnification

Example: 10× eyepiece with 40× objective = 400× total magnification

Recording and Analyzing Data

How you record and analyze your data is just as important as how you collect it.

📄 Tables and Graphs

Tables should:

Have clear headings with units
Show repeated readings where appropriate
Include calculated means for repeated measurements
Present data in a logical order

Graphs should:

Have labeled axes with units
Use appropriate scales
Plot points accurately
Include a title
Independent variable on x-axis, dependent on y-axis

📈 Analyzing Results

When analyzing your data, consider:

Patterns and trends in your results
Whether your results support your hypothesis
How your results compare to scientific theory
Possible sources of error in your experiment
The reliability of your data (consistency of repeats)
The validity of your conclusions (did you test what you intended to?)

Evaluating Investigations

Every scientific investigation has limitations. Being able to evaluate your work critically is an important skill.

Common Sources of Error

Consider these potential issues in your practical work:

Systematic errors: Consistent errors in one direction, often due to equipment calibration
Random errors: Unpredictable variations in measurements
Human errors: Mistakes in reading instruments or following procedures
Environmental factors: Uncontrolled variables like room temperature

Case Study: Investigating Enzyme Activity

A common IGCSE practical involves investigating how temperature affects enzyme activity. Students often use catalase (from potato or liver) and hydrogen peroxide, measuring oxygen production over time.

Common evaluation points:

Difficulty maintaining constant temperatures
Variations in enzyme concentration between samples
Challenges in accurately measuring gas production
Limited time leading to fewer temperature points tested

Improvements might include: using a water bath for better temperature control, standardizing enzyme extraction method, using gas syringes for more accurate measurement and testing more temperature points.

Practical Skills Checklist

Use this checklist to ensure you're prepared for practical assessments:

✅ Planning Skills

Can you identify variables in an experiment?
Can you write a clear hypothesis?
Can you design a method that controls variables?
Do you know how to determine sample size and repeats?
Can you select appropriate equipment?
Do you understand safety considerations?

✅ Implementation Skills

Can you follow a method accurately?
Can you use laboratory equipment correctly?
Can you make and record accurate measurements?
Can you organize data in appropriate tables?
Can you work safely and tidily?
Can you adapt if things don't go as planned?

Remember, practical skills develop with practice. The more hands-on work you do, the more confident you'll become. Even if you're revising for a theory exam, understanding practical techniques will help you answer questions about experimental design and data analysis.

🧠 Test Your Knowledge!