Home

Biology

Biology practicals

Investigating specimens using microscopes

Select Lesson

Exam Board

Select an option

Biology practicals

Investigating specimens using microscopes

Investigating the effect of pH on amylase activity

Investigating molecules in food using food tests

Investigating osmosis in potatoes

Investigating the effect of antimicrobials

Investigating limiting factors of photosynthesis

Investigating the rate of respiration

Using field-work techniques

Ecosystems and material cycles

Ecosystems, competition and environmental changes

Trophic levels and biomass transfer

Human impacts on biodiversity

Conservation and maintaining biodiversity

The carbon cycle

The water cycle

Obtaining potable water

The nitrogen cycle

Pollution indicators - Higher

Decomposition and biogas

Exchange and transport in animals

Specialised exchange surfaces

Factors affecting the rate of diffusion

Human circulatory system

Aerobic and anaerobic respiration

Animal coordination, control and homeostasis

The human endocrine system

Hormones: adrenaline and thyroxine - Higher

Hormones in human reproduction

Treating infertility - Higher

Homeostasis and blood glucose

Controlling body temperature

The urinary system

Plant structures and their functions

Photosynthesis and limiting factors

Factors limiting the rate of photosynthesis - Higher

Water and mineral transport in plants

Plant adaptations

Plant hormones

Health, disease and the development of medicines

The relationship between health and disease

Communicable disease

Sexually transmitted infections

How the body fights disease

Vaccination, immunisation and medicines

Aseptic techniques

Drug development and testing

Monoclonal antibodies and their uses - Higher

Non-communicable diseases

Calculating BMI and the waist-to-hip ratio

Cardiovascular disease and treatment

Plant defences and diseases

Natural selection and genetic modification

Evolution by natural selection

Fossils as evidence for evolution

Classifying living organisms

Selective breeding

Uses and evaluation of genetic engineering

The process of genetic engineering - Higher

Uses of genetic engineering

Genetics

Meiosis, sexual and asexual reproduction

Sexual and asexual reproduction

DNA: structure, genes and chromosomes

Protein synthesis - Higher

Inheritance and genetic diagrams

Inherited disorders

Blood groups, co-dominance and haemophilia

Types and sources of variation

The human genome project

Cells and control

The cell cycle and stages of mitosis

Cell differentiation, stem cells and ethics

The structure of the brain

The nervous system and the reflex arc

The eye: structure, reflexes and defects

Key concepts

Eukaryotic and prokaryotic cells

Specialised animal and plant cells

Types of microscopes and calculations

Enzymes

Calorimetry and energy calculations

Transport systems in cells

Practical skills

Measuring techniques

Safety and ethics

Designing experiments

Methods of heating substances

Working with electronics

Random sampling and sampling methods

Comparing results using percentage change

Working scientifically

The scientific method

Science communication and ethics

Evaluating risks and hazards

Collecting data

Processing and presenting data

Units and equations

Structuring a scientific report and drawing conclusions

Uncertainties and evaluations

Explainer Video

Tutor: Holly

Summary

Investigating specimens using microscopes

In a nutshell

Cells and other microscopic specimens can be viewed using a light microscope. It is also important to be able to draw good scientific drawings and identify the structures that you can see under the microscope. Using the power of the microscope lenses, the total magnification of the image can be calculated.

Equations

These are the equations that you will need to know for these microscopy practicals.

$total\space magnification = eyepiece \space lens \space magnification\times objective \space lens \space magnification$

$magnification = \frac{image\space size}{real\space size}$

Quantitative units

The specimens you will be examining are very small so you will need to know how to express their size using the following units.

Unit name	Unit	Standard form
$millimetre$	$mm$	$\times10{^-}{^3}\space m$
$micrometre$	$\mu m$	$\times10{^-}{^6}\space m$
$nanometre$	$nm$	$\times10{^-}{^9}\space m$
$picometre$	$pm$	$\times10{^-}{^1}{^2}\space m$

Equipment

The following equipment can be used to view microscopic specimen.

Equipment	Use
Microscope	To view the specimens.
Microscope slide	To hold the specimen so it can be viewed under the microscope.
Water	To place a drop on the slide and prevent the specimen drying out.
Cotton swab	To collect cheek cells.
Pipette	Used to put a drop of water on the slide.
Tweezers	To transfer the specimen onto the slide.
Stain	A stain is used if the specimen is colourless. Staining the specimen will make it easier to see.
Coverslip	A small piece of glass that is put on top of the specimen on the slide to flatten the specimen and stop the slide from drying out.
Filter paper	To absorb excess stain.

Experiment 1: Preparing a specimen on a microscope slide

Specimens must be prepared before they are viewed under a microscope. You must be careful when you do this as you don't want to damage the specimen. Onion cells and cheek cells are most commonly used for plant and animal cells respectively.

Experimental variables

Every experiment will have an independent, dependent and constant variable. The independent variable is the variable that you change. The dependent variable is the variable which depends on the independent variable, therefore it is the one you measure. The control variable is the variable that is kept the same during the experiments.

Independent variable	$The\space specimen\space you\space are\space examining.$
Dependent variable	$Magnification.$
Control variable	$The\space type\space of\space dye\space used\space and\space the\space stage\space micrometer.$

Safety precautions

When carrying out experiments it is very important to consider the safety precautions so nobody gets hurt.

Hazard	Risk	Safety measure
Stains	The stains may stain your skin.	Wear gloves when using the stains or just be careful not to get the stain on your skin or clothes.
Coverslips and microscope slides	These are made of glass and may cut you.	Be careful when handling the coverslips and microscope slides.

Method for preparing an animal cell specimen

Biology; Biology practicals; KS4 Year 10; Investigating specimens using microscopes

1.	Collect the specimen. Use a cotton swab to swab the inside of your cheek.
2.	Using a pipette, add a drop of water to the slide.
3.	Gently rub the cotton swab on the slide.
4.	Add a drop of methylene blue stain to the slide. This stain turns the nucleus of the cell blue.
5.	Using tweezers, place a coverslip over the specimen.
6.	Use filter paper to absorb any excess stain.

Method for preparing a plant cell specimen

1.	Collect the specimen. Using the tweezers, peel away a layer of skin from an onion.
2.	Using a pipette, add a drop of water to the slide.
3.	Using the tweezers, place the onion skin layer on the slide. *Note:* Make sure it is laying flat on the slide and there are no air bubbles.
4.	Add a drop of iodine stain to the slide.
5.	Using tweezers, place a coverslip over the specimen.
6.	Use filter paper to absorb any excess stain.

Experiment 2: Viewing the specimen using a microscope

Parts of a microscope

	Part of the microscope	Explanation
1.	Eyepiece	The eyepiece is what you look through to see the magnified image. The eyepiece contains the eyepiece lens which magnifies the specimen to produce the image you can see.
2.	Body tube	The body tube separates the eyepiece and objective lenses.
3.	Rough focusing knob	The rough focusing knob is used to move the stage to bring the image into focus.
4.	Fine focusing knob	The fine focusing knob is used to bring the image into focus after the rough focusing knob is used.
5.	Objective lenses	The objective lens magnifies the specimen. There are usually three lenses with increasing power. The highest-powered lens will create a greater magnification.
6.	Handle	The microscope should be held by the handle.
7.	Stage	The stage is where the slide is placed.
8.	Mirror	The mirror should be angled towards a light source and up through the hole in the stage. This provides the light that enables you to see the image. *Note:* In some microscopes there will be a lightbulb instead of a mirror.

Method

1.	Place the prepared slide onto the stage and clip it in place so the specimen is positioned where the light will come through.
2.	Select the lowest powered objective lens. Rotate the lens so it is over the slide.
3.	Use the coarse adjustment knob to move the stage. Move the stage up so the slide is just underneath the objective lens.
4.	Look down the eyepiece lens and use the coarse adjustment knob to move the stage downwards until the specimen is almost in focus.
5.	Use the fine adjustment knob to bring the specimen into focus. The image should now be clear.
6.	If you need a greater magnification, switch to a higher powered lens and refocus the image.

Analysis

To report on what you have observed through the microscope, you need to calculate the size of the specimen, report on the magnification and be able to draw biological drawings.

Here are two methods for calculating the size of the specimen.

Method one

1.	Place a clear ruler on the stage.
2.	Measure the diameter of the circle that you can see when looking down the eyepiece. This is your field of view (FOV).
3.	If you increase the magnification, recalculate your FOV. Note: The FOV allows you to estimate the size of the specimen.

Method two

1.	Place an eyepiece graticule (A) on the eyepiece lens. If you look down the lens you should now see a scale. Before being able to measure the cells, you must calibrate the eyepiece graticule. This means you need to find out the distance that each division on the eyepiece graticule represents. *Note:* Each objective lens will give a different value so you must calibrate the eyepiece graticule each time you use a new lens.
2.	Remove the slide with your specimen and place a stage micrometer (B) onto the stage. Note: A stage micrometer is a slide with an accurate scale on it.
3.	Line up the stage micrometer and the eyepiece graticule. Select a set measurement on the stage micrometer and count the number of divisions on the eyepiece graticule that fit in this set measurement. Using the stage micrometer, calculate the distance (in micrometers) of one division on the eyepiece graticule.
4.	Remove the stage micrometer and use the calibrated eyepiece graticule to measure the cell on your original specimen slide.

Calculating the magnification

You can use the equation below to work out the total magnification if you know the magnification of both the eyepiece lens and the objective lens.

total\space magnification = eyepiece \space lens \space magnification\times objective \space lens \space magnification

If you do not know the magnification of the lenses, you can still work out the magnification. To do this, you will need to measure the image and know the real size of the specimen.

magnification = \frac{image\space size}{real\space size}

Note: The units for the image size and the real size should be the same. The units shown in the table at the top of this summary can be used.

Creating biological drawings

Biological drawings are needed to show what you have seen down the microscope. These are different to normal drawings and it is important that you follow the steps below.

1.	Use a sharp pencil to draw the outline of all the main features you can see.
2.	Make sure your drawing takes up at least half of the space you are given and that all of the parts are proportionally the correct size.
3.	Draw straight lines from each structures and write the name of the structure.
4.	Include the magnification you have used and a scale bar.

Example

Evaluation

After completing the experiment, you must comment on the quality of your data. You should also think about how your method could be improved. If you have calculated the magnification from the actual size of the specimen and the size of the image created, you can compare this to the actual magnification you used. The two values for magnification should be the same.

The most common mistake with calculating the magnification is to reverse the formula. In order to calculate the correct magnification, it is also crucial to correctly calibrate the eyepiece graticule (or calculate the FOV). If you do not do this correctly, the sizes will be incorrect. Therefore, your result for the magnification will also be incorrect.

Learn with Basics

Length:

Unit 1

Animal cells, plant cells, and unicellular organisms

Unit 2

How to observe cells under a microscope

Jump Ahead

Optional

Unit 3

Investigating specimens using microscopes

Final Test

Create an account to complete the exercises

FAQs - Frequently Asked Questions

When is a stain used?

A stain is used if the specimen is colourless. Staining the specimen will make it easier to see.

Which cells are commonly used when studying plant and animal cells?

Onion cells and cheek cells are most commonly used for plant and animal cells respectively.

What is a coverslip?

A coverslip is a small piece of glass that is put on top of the specimen on the slide to flatten the specimen and stop the slide from drying out.

Home

Biology

Biology practicals

Investigating specimens using microscopes

Videos

Summary

Exercises

Select Lesson

Exam Board

Select an option

Biology practicals

Investigating specimens using microscopes

Investigating the effect of pH on amylase activity

Investigating molecules in food using food tests

Investigating osmosis in potatoes

Investigating the effect of antimicrobials

Investigating limiting factors of photosynthesis

Investigating the rate of respiration

Using field-work techniques

Ecosystems and material cycles

Ecosystems, competition and environmental changes

Trophic levels and biomass transfer

Human impacts on biodiversity

Conservation and maintaining biodiversity

The carbon cycle

The water cycle

Obtaining potable water

The nitrogen cycle

Pollution indicators - Higher

Decomposition and biogas

Exchange and transport in animals

Specialised exchange surfaces

Factors affecting the rate of diffusion

Human circulatory system

Aerobic and anaerobic respiration

Animal coordination, control and homeostasis

The human endocrine system

Hormones: adrenaline and thyroxine - Higher

Hormones in human reproduction

Treating infertility - Higher

Homeostasis and blood glucose

Controlling body temperature

The urinary system

Plant structures and their functions

Photosynthesis and limiting factors

Factors limiting the rate of photosynthesis - Higher

Water and mineral transport in plants

Plant adaptations

Plant hormones

Health, disease and the development of medicines

The relationship between health and disease

Communicable disease

Sexually transmitted infections

How the body fights disease

Vaccination, immunisation and medicines

Aseptic techniques

Drug development and testing

Monoclonal antibodies and their uses - Higher

Non-communicable diseases

Calculating BMI and the waist-to-hip ratio

Cardiovascular disease and treatment

Plant defences and diseases

Natural selection and genetic modification

Evolution by natural selection

Fossils as evidence for evolution

Classifying living organisms

Selective breeding

Uses and evaluation of genetic engineering

The process of genetic engineering - Higher

Uses of genetic engineering

Genetics

Meiosis, sexual and asexual reproduction

Sexual and asexual reproduction

DNA: structure, genes and chromosomes

Protein synthesis - Higher

Inheritance and genetic diagrams

Inherited disorders

Blood groups, co-dominance and haemophilia

Types and sources of variation

The human genome project

Cells and control

The cell cycle and stages of mitosis

Cell differentiation, stem cells and ethics

The structure of the brain

The nervous system and the reflex arc

The eye: structure, reflexes and defects

Key concepts

Eukaryotic and prokaryotic cells

Specialised animal and plant cells

Types of microscopes and calculations

Enzymes

Calorimetry and energy calculations

Transport systems in cells

Practical skills

Measuring techniques

Safety and ethics

Designing experiments

Methods of heating substances

Working with electronics

Random sampling and sampling methods

Comparing results using percentage change

Working scientifically

The scientific method

Science communication and ethics

Evaluating risks and hazards

Collecting data

Processing and presenting data

Units and equations

Structuring a scientific report and drawing conclusions

Uncertainties and evaluations

Explainer Video

Tutor: Holly

Summary

Investigating specimens using microscopes

In a nutshell

Equations

These are the equations that you will need to know for these microscopy practicals.

$total\space magnification = eyepiece \space lens \space magnification\times objective \space lens \space magnification$

$magnification = \frac{image\space size}{real\space size}$

Quantitative units

The specimens you will be examining are very small so you will need to know how to express their size using the following units.

Unit name	Unit	Standard form
$millimetre$	$mm$	$\times10{^-}{^3}\space m$
$micrometre$	$\mu m$	$\times10{^-}{^6}\space m$
$nanometre$	$nm$	$\times10{^-}{^9}\space m$
$picometre$	$pm$	$\times10{^-}{^1}{^2}\space m$

Equipment

The following equipment can be used to view microscopic specimen.

Equipment	Use
Microscope	To view the specimens.
Microscope slide	To hold the specimen so it can be viewed under the microscope.
Water	To place a drop on the slide and prevent the specimen drying out.
Cotton swab	To collect cheek cells.
Pipette	Used to put a drop of water on the slide.
Tweezers	To transfer the specimen onto the slide.
Stain	A stain is used if the specimen is colourless. Staining the specimen will make it easier to see.
Coverslip	A small piece of glass that is put on top of the specimen on the slide to flatten the specimen and stop the slide from drying out.
Filter paper	To absorb excess stain.

Experiment 1: Preparing a specimen on a microscope slide

Experimental variables

Independent variable	$The\space specimen\space you\space are\space examining.$
Dependent variable	$Magnification.$
Control variable	$The\space type\space of\space dye\space used\space and\space the\space stage\space micrometer.$

Safety precautions

When carrying out experiments it is very important to consider the safety precautions so nobody gets hurt.

Hazard	Risk	Safety measure
Stains	The stains may stain your skin.	Wear gloves when using the stains or just be careful not to get the stain on your skin or clothes.
Coverslips and microscope slides	These are made of glass and may cut you.	Be careful when handling the coverslips and microscope slides.

Method for preparing an animal cell specimen

1.	Collect the specimen. Use a cotton swab to swab the inside of your cheek.
2.	Using a pipette, add a drop of water to the slide.
3.	Gently rub the cotton swab on the slide.
4.	Add a drop of methylene blue stain to the slide. This stain turns the nucleus of the cell blue.
5.	Using tweezers, place a coverslip over the specimen.
6.	Use filter paper to absorb any excess stain.

Method for preparing a plant cell specimen

1.	Collect the specimen. Using the tweezers, peel away a layer of skin from an onion.
2.	Using a pipette, add a drop of water to the slide.
3.	Using the tweezers, place the onion skin layer on the slide. *Note:* Make sure it is laying flat on the slide and there are no air bubbles.
4.	Add a drop of iodine stain to the slide.
5.	Using tweezers, place a coverslip over the specimen.
6.	Use filter paper to absorb any excess stain.

Experiment 2: Viewing the specimen using a microscope

Parts of a microscope

	Part of the microscope	Explanation
1.	Eyepiece	The eyepiece is what you look through to see the magnified image. The eyepiece contains the eyepiece lens which magnifies the specimen to produce the image you can see.
2.	Body tube	The body tube separates the eyepiece and objective lenses.
3.	Rough focusing knob	The rough focusing knob is used to move the stage to bring the image into focus.
4.	Fine focusing knob	The fine focusing knob is used to bring the image into focus after the rough focusing knob is used.
5.	Objective lenses	The objective lens magnifies the specimen. There are usually three lenses with increasing power. The highest-powered lens will create a greater magnification.
6.	Handle	The microscope should be held by the handle.
7.	Stage	The stage is where the slide is placed.
8.	Mirror	The mirror should be angled towards a light source and up through the hole in the stage. This provides the light that enables you to see the image. *Note:* In some microscopes there will be a lightbulb instead of a mirror.

Method

1.	Place the prepared slide onto the stage and clip it in place so the specimen is positioned where the light will come through.
2.	Select the lowest powered objective lens. Rotate the lens so it is over the slide.
3.	Use the coarse adjustment knob to move the stage. Move the stage up so the slide is just underneath the objective lens.
4.	Look down the eyepiece lens and use the coarse adjustment knob to move the stage downwards until the specimen is almost in focus.
5.	Use the fine adjustment knob to bring the specimen into focus. The image should now be clear.
6.	If you need a greater magnification, switch to a higher powered lens and refocus the image.

Analysis

To report on what you have observed through the microscope, you need to calculate the size of the specimen, report on the magnification and be able to draw biological drawings.

Here are two methods for calculating the size of the specimen.

Method one

1.	Place a clear ruler on the stage.
2.	Measure the diameter of the circle that you can see when looking down the eyepiece. This is your field of view (FOV).
3.	If you increase the magnification, recalculate your FOV. Note: The FOV allows you to estimate the size of the specimen.

Method two

1.	Place an eyepiece graticule (A) on the eyepiece lens. If you look down the lens you should now see a scale. Before being able to measure the cells, you must calibrate the eyepiece graticule. This means you need to find out the distance that each division on the eyepiece graticule represents. *Note:* Each objective lens will give a different value so you must calibrate the eyepiece graticule each time you use a new lens.
2.	Remove the slide with your specimen and place a stage micrometer (B) onto the stage. Note: A stage micrometer is a slide with an accurate scale on it.
3.	Line up the stage micrometer and the eyepiece graticule. Select a set measurement on the stage micrometer and count the number of divisions on the eyepiece graticule that fit in this set measurement. Using the stage micrometer, calculate the distance (in micrometers) of one division on the eyepiece graticule.
4.	Remove the stage micrometer and use the calibrated eyepiece graticule to measure the cell on your original specimen slide.

Calculating the magnification

You can use the equation below to work out the total magnification if you know the magnification of both the eyepiece lens and the objective lens.

total\space magnification = eyepiece \space lens \space magnification\times objective \space lens \space magnification

If you do not know the magnification of the lenses, you can still work out the magnification. To do this, you will need to measure the image and know the real size of the specimen.

magnification = \frac{image\space size}{real\space size}

Note: The units for the image size and the real size should be the same. The units shown in the table at the top of this summary can be used.

Creating biological drawings

Biological drawings are needed to show what you have seen down the microscope. These are different to normal drawings and it is important that you follow the steps below.

1.	Use a sharp pencil to draw the outline of all the main features you can see.
2.	Make sure your drawing takes up at least half of the space you are given and that all of the parts are proportionally the correct size.
3.	Draw straight lines from each structures and write the name of the structure.
4.	Include the magnification you have used and a scale bar.

Example

Evaluation

Learn with Basics

Length:

Unit 1

Animal cells, plant cells, and unicellular organisms

Unit 2

How to observe cells under a microscope

Jump Ahead

Optional

Unit 3

Investigating specimens using microscopes

Final Test

Create an account to complete the exercises

FAQs - Frequently Asked Questions

When is a stain used?

A stain is used if the specimen is colourless. Staining the specimen will make it easier to see.

Which cells are commonly used when studying plant and animal cells?

Onion cells and cheek cells are most commonly used for plant and animal cells respectively.

What is a coverslip?

A coverslip is a small piece of glass that is put on top of the specimen on the slide to flatten the specimen and stop the slide from drying out.

Investigating specimens using microscopes

Videos

Summary

Exercises

Select Lesson

Exam Board

Biology practicals

Ecosystems and material cycles

Exchange and transport in animals

Animal coordination, control and homeostasis

Plant structures and their functions

Health, disease and the development of medicines

Natural selection and genetic modification

Genetics

Cells and control

Key concepts

Practical skills

Working scientifically

Explainer Video

Summary

Investigating specimens using microscopes

In a nutshell

Equations

Quantitative units

Unit name

Unit

Standard form

Equipment

Equipment

Use

Experiment 1: Preparing a specimen on a microscope slide

Experimental variables

Safety precautions

Hazard

Risk

Safety measure

Method for preparing an animal cell specimen

Method for preparing a plant cell specimen

Experiment 2: Viewing the specimen using a microscope

Parts of a microscope

Part of the microscope

Explanation

Method

Analysis

Example

Evaluation

Learn with Basics

Unit 1

Animal cells, plant cells, and unicellular organisms

Unit 2

How to observe cells under a microscope

Jump Ahead

Unit 3

Investigating specimens using microscopes

Final Test

FAQs - Frequently Asked Questions

When is a stain used?

Which cells are commonly used when studying plant and animal cells?

What is a coverslip?

Investigating specimens using microscopes

Videos

Summary

Exercises

Select Lesson

Exam Board

Biology practicals

Ecosystems and material cycles

Exchange and transport in animals

Animal coordination, control and homeostasis

Plant structures and their functions

Health, disease and the development of medicines

Natural selection and genetic modification

Genetics

Cells and control

Key concepts

Practical skills

Working scientifically

Explainer Video

Summary

Investigating specimens using microscopes