INTRODUCTION TO BIOLOGY

WHAT IS BIOLOGY?

The word Biology is delivered from two Greek words, namely: Bios – means life and Logos – means study

Therefore, Biology is the study of life

Another meaning of biology

Biology: is a branch of science which deals with the study of living things.

A person who studies biology is called Biologist.

BRANCHES OF BIOLOGY

There are two main branches of biology, namely

(i) Zoology

(ii) Botany

(i) ZOOLOGY

Is the study of animals. Examples of animals are human beings, goat and birds

A person who study zoology is called Zoologist

(ii) BOTANY

Is the study of plants. Examples of plants beans and maize

– A person who study botany is called Botanist

OTHER BRACHES OF BIOLOGY

The following are other branches of biology:

1. MICROBIOLOGY

Is the study of microorganism

– Fern plants

– Pines, cypress and

– Christmas tree

Microorganisms are very small organisms that cannot be seen with naked eyes.

Examples of microorganisms

-Bacteria

-Viruses

A person who studies microbiology is called microbiologist

2. BACTERIOLOGY

Is the study bacteria

Examples of bacteria

– Salmonella typhi

-Vibrio cholera

∆A person who studies bacteriology is called bacteriologist

3. VIROLOGY

Is the study of viruses Example of fungi

-HIV (Human Immunodeficiency Virus)

-Corona virus

-A person who studies virology is called virologist

4. MYCOLOGY

Is the study of fungi

Examples of fungi

– Yeast

-Mushroom

-A person who studies mycology is called mycologist

5. GENETICS

Is the study of inheritance

– A person who studies genetics is called geneticist

6. CYTOLOGY

Is the study of cells

– A person who studies cytology is called cytologist

7. ANATOMY

Is the study of internal structures of living things.

Example of internal structures of living things

– Heart

– Brain

– Kidneys     –

Lungs

– A person who studies anatomy is called anatomist

8. ENTOMOLOGY

Is the study of insects

Example of insects

-Locust     –

– Grasshoppers

– Butterflies

– Butterflies

– A person who studies entomology is called entomologist

9. PHYSIOLGY

Is the study of how body structures of an organism function

– A person who studies physiology is called physiologist

10. HOLTICULTURE

Is the science and art of growing fruits, vegetables, flowers or ornamental plants.

11. IMMUNOLOGY

Is the study of body immune system

– A person who studies immunology is called immunologist

12. PARASITOLOGY

Is the study of parasites

Example of parasites

-Plasmodium

– Some fungi

-Viruses

– Some bacteria

– A person who studies parasitology is called parasitologist

13. TAXONOMY

Is the study of classification

– A person who studies taxonomy is called taxonomist

14. ECOLOGY

Is the study of relationship between organisms and their environment

– A person who studies ecology is called ecologist

15.    ORNITHOLOGY

Is the study of birds Examples of birds

– Hen

– Hawk

– Penguin

– Vulture

– A person who studies ornithology is called ornithologist.

16. ICHTHYOLOGY

Is the study of fish.

17. MORPHOLOGY

Is the study of external forms and structures of organisms

THE IMPORTANCE OF STUDYING BIOLOGY

The following is an outline of why the study of biology is important:

(i)    It helps us to understand ourselves better.

(ii)    Biology helps us to understand our environment better and how to conserve it

(iii)    Biology helps us to know the causes, transmissions, signs and symptoms of diseases.

(iv)    Biology enables scientists to come up with ways of preventing, treating and curing diseases.

(v)    Biology enables researchers to come up with improved breeds of crops and animals.

(vi)    It is a foundation for getting into careers such as medicine and agriculture.

(vii)    Biology helps us to answer some fundamental questions such as, what do we need to survive?

(viii)    Biology helps us to get professional people like doctors, pharmacists and teachers.

(ix)    It encourages international cooperation.

(x)    It helps us to acquire research skills such as measuring, observing, analysis and making conclusions.

QUESTION

1. Form one students in a certain secondary school were interested to know why it is necessary to study biology. Assume you are a Biology teacher: educate these students on the importance of studying Biology by giving six (6) points.

2. Outline six reasons why it is important to study Biology?

3. Biology is more than a study of animals and plants. Explain

4. Distinguish between unicellular organisms from multicellular organisms giving an example in each case.

5. How Botany differs from Zoology?

CHARACTERISTICS OF LIVING THINGS

There are seven (7) characteristics (life processes) that distinguish living things from nonliving things. These are: –

(i)    Movement and locomotion

(ii)    Respiration

(iii)    Nutrition

(iv)    Irritability or sensitivity

(v)    Growth

(vi)    Excretion

(vii)    Reproduction

NB: For easy study of these characteristics the word MR NIGER can be used

(i) MOVEMENT

Is the act of changing position or postures by the whole organism or part of an organism.

– Living things moves in order to search for food, water, mate, light and to escape from dangers.

– It can occur at a cellular level e.g. cytoplasmic streaming in amoeba and it can also occur in an organ level. E.g. Closing and opening of leaves, folding of leaves in plants.

Example of movement

– Singing

– Closing and opening

– Yawning of leaves

– Clapping hands

LOCOMOTION

Is the change in position by the whole body of an organism from one place and another. Example of locomotion

– Walking     – Swimming

– Running     – Crawling

(ii) RESPIRATION

Is the process of breaking down of food materials within the cells to release energy.

– Living things need energy for movement, growth and development, and functioning of body organs.

(iii) IRRITABILITY (SENSITIVITY)

Is the ability of an organism to detect and respond to a stimulus.

Stimulus

Is a change in the external and internal environment of an organism.

Examples of stimulus

– Light

– Temperature

– Cold

– Wind

-An alarm clocks

– A smell of food

– A fly landing on your eye.

Response

Is the change shown by an organism in reaction to a stimulus

Example of response

– Salivation when food smells

– Blinking when a fly landing on the eye

– Picking up a phone after hearing it ringing

(iv) NUTRITION (FEEDING)

Is the process of taking in food, absorb and assimilate nutrients

– Nutrition is the characteristic of living things which is the basic difference between plants and animals.

– Plants make their own food through photosynthesis process hence called autotrophs

– Animals get their food by eating other living things hence called heterotrophs.

– All living things need food to provide energy for such activities such as growth, repair and health.

(v) GROWTH AND DEVELOPMENT

Growth: Is an irreversible and permanent increase in size and dry mass of an organism.

– All living things grow and build up their bodies.

– Animals grow until they reach certain adult size, but most plants can grow continuously throughout their lives.

Example of growth

– Increase in body weight

– Increase in body height

– Increase in body size and shape

DEVELOPMENT

Is the change in the complexity of an organism.

Example of development

– Emergence of a new structure

– Ripening of fruits.

(vi) REPRODUCTION

Is the process by which living things produce new individuals of their kind.

– All living things reproduce, to replace organisms lost by death.

– Human beings bear babies; birds hatch chicks; and plants produce seedlings as new organisms, which eventually grow to mature organisms to replace those lost by deaths.

(vii) EXCRETION

Is the process of removing metabolic waste products from the body of living organisms.

– Excretion is shown by both animals and plants

Example of waste products

– Carbon dioxide

-Urea

– Excess water

-Ammonia

– Waste products are removed from the body by excretory organs such skin, kidneys, lungs and liver

DIFFERENCES BETWEEN LIVING THINGS AND NON-LIVING THINGS     

RELATIONSHIP BETWEEN BIOLOGY AND OTHER RELATED FIELDS

Biology relates with many other fields, some of them are:

(i)    Agriculture

(ii)    Medicine

(iii) Pharmacy

(iv)    Nutrition

(v)    Forestry

(vi)    Veterinary science

RELATIONSHIP BETWEEN BIOLOGY AND OTHER FIELD

SCIENTIFIC PROCESSES IN BIOLOGY

The study of biology involves scientific processes.

– Scientific processes are conducted in order to solve different life problems and help us to understand well our environment.

WAYS USED IN CARRYING OUT SCIENTIFIC PROCESSES IN BIOLOGY

There are three basic skills that are needed in studying biology (scientific studies)

(a)    Observation

(b)    Measurement

(c)    Scientific method

(a) OBSERVATION

This method is done by using sense organs

– All scientific investigations involve observation using sense organs

SENSE ORGANS USED IN OBSERVATION

There are five sense organs used in observation, namely;

(i) Eyes

(ii) Ears

(iii) Nose

(iv) Tongue

(v) Skin

THE FUNCTION OF EACH SENSE ORGAN

EYES

Used for seeing or vision.

Example: shape, colour and size of the object

SKIN

Used for touch

Used to detect pain, heat, cold and pressure

Example: texture of an object, temperature and sharpness of an object.

NOSE

Used for smelling.

Example: smell of chemicals or foods

EARS

Used for hearing.

Example: sounds of living and non-living things

TONGUE

Used for tasting.

Example: tastes of different specimens such as sugar and salt.

Example: If you have a coconut, you can use sense organs to determine that:

(i) It is round – by seeing

(ii) It contains a liquid – by hearing the sound when shaken

(iii) It has rough husk (surface) – by touching

(iv) It has good smell – by smelling

(v) It has good taste – by tasting after breaking the coconut

WEAKNESS OF USING SENSE ORGANS IN MAKING OBSERVATION

(i) Sense organs are based on person’s ideas rather than facts.

(ii) Sense organs alone cannot be enough to give out all the details in accuracy way.

ADVANTAGE OF USING SENSE ORGANS IN OBSERVATION

– Enables us to study living things.

PRECAUTIONS WHEN USING SENSE ORGANS IN OBSERVATION

(i) Avoid smelling everything in the laboratory without permission from your teacher or laboratory technician.

(ii) Avoid tasting anything in the laboratory unless you are told do so by the teacher or laboratory technician.

Topic 1: Introduction To Biology – Biology Notes Form 1

(b) MEASUREMENT

Is the system of using specific instruments and units to make investigations. Or is the process of assigning numerical values to different things in order to find their size or magnitude.

– For any meaningful measurement in Biology, we need to state the physical quantity (parameter) to be measured and its units.

– The units applied in measurement are International System of units (SI-Units).

COMMON PHYSICAL QUANTITIES (PARAMETERS) MEASURED IN BIOLOGY

The following are common physical quantities (parameters) measured in biology with their standard units and instrument used for measuring each parameter:

1. LENGTH (l)

Is the distance between any two points

– The instrument used to measure length is called ruler or tape measure

– It is expressed in millimetres (mm), centimetres (cm), metres (m), and kilometers (km)

Where:

1cm = 10 mm

1m = 100 cm

1km = 1000 m

WORKED EXAMPLES

1.    Convert the following units into millimeter

(i)    10 cm

(ii)    10 km

(iii)    50 m

2.    Change the following units as directed

(i)    1000km to cm

(ii)    320 to km

(iii) 200mm to km

(iv) 900km to m

2. MASS (m)

Is the quantity (amount) of matter in the object

◊ The instrument that can be used to measure mass is called weighing balance such as beam balance, electronic balance

◊ It is expressed in grams (g) or kilograms (kg)

Where

1kg = 1000g

WORKED EXAMPLES

1.    Convert the following units as directed

(i)    70g into kg

(ii)    40g into kg

(iii)   10kg into g

3. TEMPERATURE

Is the measure of relative hotness and coldness of a body or object

– The instrument used to measure temperature is called thermometer

– It is expressed in Kelvin (K), degrees Celsius (℃) and degrees Fahrenheit (℉)

– The normal body temperature is between 36℃ to 37℃

Temperature in different units can be calculated by using the following formula

(i)    K = ℃ + 273

(ii)    ℉ = ( × ℃) + 32

(iii)    ℃ = × (℉ − 32)

WORKED EXAMPLES

1. Convert the following units into Kelvin (K)

(i)    85℃

Solution

From: K = ℃ + 273

Where: ℃ = 85

K = 85 + 273 = 358

Therefore: 85℃ = 𝟑𝟓𝟖K

(ii)    −450℃

Solution

From: K = ℃ + 273

Where: ℃ = −450

K = −450 + 273 = −177

Therefore: −𝟒𝟓𝟎℃ = −𝟏𝟕𝟕K

(iii)115℃

(iv) 40℉

2.    Convert the following units into degrees Celcius (℃)

(i)    20K

(ii)    40℉

(iii)100℉

3.    Convert the following temperature into degrees Fahrenheit (℉)

(i)    85℃     (iii)100℃

(ii)    115℃     (iv) 20K

4. PULSE RATE

Is the number of times the heart beats per minute.

– The instrument used to measure pulse rate is called stethoscope

– It is expressed in number of heart beats per minute.

NB: For a person in normal health, the pulse rate occurs 72 times per minute but for the embryo of human being aged about 60 days, the pulse rates is 150 beats per minute

Parts of the body where Pulse is felt

Pulse is felt in any artery by placing the index and middle fingers on:

– The neck

– Behind the knee,

– The wrist

– On the side of elbow

– Below ears

– Near the ankle joint.

NB: Do not use the thumb to make pulse because it has its own pulse.

(c) SCIENTIFIC METHOD

Is a set of steps that a scientist follows to solve a problem about nature.

OR is an organized set of guidelines used to solve scientific problem

– The scientific method is also called scientific process or scientific procedure

IMPORTANCE OF SCIENTIFIC METHOD

(i)    It helps us to solve scientific problem

(ii)    It helps us to gain new knowledge

(iii) It helps us to conduct project work or carry out field work

STEPS OF THE SCIENTIFIC METHOD

The scientific method involves the following steps;

1.    Identifying a problem

2.    Formulating a hypothesis

3.    Conducting experiment

4.    Collecting data

5.    Analysing data

6.    Interpreting data

7.    Conclusion

1. IDENTIFYING THE PROBLEM

This is the first step in the scientific method where a problem is recognized or identified.

– In our day to day life one often comes across questions which require explanations or answers.

PROBLEM

Is a specific event observed in the environment.

For example

In a certain region of Tanzania, Agricultural officers observed tomatoes yield was low despite frequent irrigation, correct planting techniques, timely planting and adequate sunlight.

Question (problem could be)

What could have caused poor yield of tomatoes in Jama’s garden despite all the efforts made?”

2. FORMULATING A HYPOTHESIS

This is the second step in the scientific method where a possible answer to a question is suggested.

Hypothesis

Is an intelligent guess which tries to answer the observed problem.

Or is a tentative explanation for the observation made.

– A hypothesis from the above problem could be that the low yield of tomatoes is caused by poor soil fertility.”

– Therefore, the agricultural officers suggested that application of fertilizer could increase the tomatoes yield.

Ways used to test hypothesis

(i) By careful observation in a natural setting

Example: Behaviour of a certain type of wild animal can be studied by carefully observing the animal in the field they live

(ii) By conducting experiment

3. EXPERIMENTATION

In this step, scientists plan and conduct an experiment

– In planning an experiment

– Scientists collect necessary information concerning the problem, determine which apparatus will be used, which materials will be required and what procedures will be followed to prove or reject the hypothesis.

Experiment

Is a test done to confirm or reject the hypothesis

– Experiment is conducted to determine if the hypothesis is correct or not.

– Experiment is repeated more times to obtain more accurate results

NB: In conducting experiment, two sets of subjects are involved:

(a) Experimental group or test experiment

(b) Control group or control experiment

(a) Test experiment

Is the one that receives treatment

Or is the experiment which is done by changing variables or factors from time to time

Example: addition of fertilizers (b) Control experiment

Is the one that does not receive treatment

Or is the experiment which is done without changing variables or factors.

Example: no addition of fertilizers

– Control experiment is usually set in order to compare it with the test experiment and to prove the hypothesis.

From our example of low tomatoes yield, a plan for investigation could be as follows: Aim of the experiment: To observe if low yield is due to poor soil fertility Requirements: Tomato seed from affected area, fertilizer Instructions:

(i) Set aside two plots and name them as: Plot A and Plot B

(ii) Subject all the two plots to the same ecological conditions

(iii) In plot A apply fertilizer as recommended by the agricultural officers

(iv) In plot B fertilizer should not be added.

(v) Harvest and compare the yields of the two plots

NB: In the above planned experiment, the plot B is not applied with fertilizer, this is a control experiment. The controlled experiment proves that the fertilizer is the one that determines the tomatoes yield.

The experiment is conducted by using variables

VARIABLES

Are conditions or factors that can change or be changed during an experiment

TYPES OF VARIABLES

There are three types of variables, namely;

(a) Dependent variable

Is the condition or factor that is investigated or observed to obtain the results of the experiment

(b) Independent variable (manipulated)

Is the condition or factor that is changed systematically to obtain different results

(c) Controlled variable

Is the condition that is kept constant during the experiment. Example light

4. COLLECTING DATA

Is the process of recording and presenting all the changes or information observed during experiment

– In this step, all changes observed during the experiment are collected and recorded.

Data

Is the information gathered during the experiment.

Or is unprocessed information that is collected from the experiment by observation or measurement.

5. DATA ANALYSIS

Is the process of translating information observed during an experiment.

– Data analysis involves comparing the results obtained and hypothesis

– Data are organized and analyzed in order to test the hypothesis, to see trends and patterns

– To enable one to see the results in an organized manner, data should be presented using different methods such as tables, bar charts, pie charts, histograms drawings or line graphs.

Example

A table below presents the data analyzed from our tomato experiment

PLOT TOMATO YIELD

A 2,300 kg

B 150 kg

6. DATA INTERPRETATION

Is the process of giving meaning of the collected data.

– In our tomato yield experiment, the data in the table above shows that there is a difference in tomato yield from the two plots.

– The yield of plot A was higher than of the plot B. this mean that, the amount of fertilizer has effect on the amount of tomato yield.

7. CONCLUSION

Is the statement that summarizes the results of the experiment conducted.

– In conclusion, a hypothesis can be accepted or rejected based on the data collected and analyzed. Example

– In our tomato yield experiment, the results have shown that the application of the right amount of fertilizer increased crop yield.

– Therefore, low tomato yield was a result of poor soil fertility.

– The results support the hypothesis that low crop yield was caused by poor soil fertility

– In this case, the hypothesis was accepted or confirmed.

– In some cases, when the hypothesis selected and involved for experiment is rejected another hypothesis is formed and an experiment is conducted again.

– Conclusion results to the formation of law, theory and principle. The steps for scientific method are summarized in the figure below.

The steps for scientific method are summarized in the figure below.     

         CONCLUSION

THE BIOLOGY LABORATORY

The word ‘laboratory’ originates from Latin name ‘laborare’ which means “a place for work”

Laboratory is a room or building designed for carrying out scientific experiments.

There are various types of laboratory such as;

(i)    Biology laboratory

(ii)    Chemistry laboratory

(iii)    Physics laboratory

(iv)    Clinical laboratory

(v)    Industrial laboratory

BIOLOGY LABORATORY

Biology laboratory is a special room or building where biological experiments are conducted.

The biology laboratory differs from other scientific laboratories in the following ways;

(i)    Biology laboratory has preserved specimens

(ii)    Biology laboratory has models of organs

(iii) Biology laboratory has microscope

(iv)    Biology laboratory has dissecting kit

(v)    Biology laboratory has charts showing different body systems and organs

(vi)    Biology laboratory has cages Cage is an enclosure made to hold animals

(vii)    Biology laboratory has aquaria (single–aquarium) Aquarium is tank made for keeping live aquatic animals

QUALITIES OF A GOOD LABORATORY

(i)    Laboratory has doors which exit outwards. This is for easy escape when accident occurs.

(ii)    Laboratory should have source of water. Water help in boiling, mounting specimens and cleaning.

(iii)    Laboratory should have source of heat. Heat is needed for experiments

(iv)    Laboratory should have electricity supply. Electricity is for lighting and electronic devices.

(v)    Laboratory should have adequate apparatus for conducting experiments

(vi)    Laboratory should have adequate storage room and cupboards. For storing apparatus and specimens

(vii)    Laboratory should have adequate space for carrying out experiments.

(viii)    Laboratory should have emergency facilities placed in area where can be reached easily. Example fire extinguishers and sand buckets

LABORATORY SAFETY RULES

Laboratory can be a dangerous place if the safety rules are not observed.

The following are some rules to ensure safety in a laboratory.

(i)    Do not enter the laboratory or do an experiment without permission from a teacher.

(ii)    Do not run, play or make noise in the laboratory. (iii) Do not eat any food or drink in the laboratory

(iv)    Do not use broken apparatus or unlabeled chemicals.

(v)    Do not take any laboratory tool or specimen out of the laboratory.

(vi)    Do not taste anything without being instructed

(vii)    Do not put laboratory equipment at the edge of benches or tables.

(viii)    Do not leave water and gas taps open

(ix)    Do not block the emergency facilities and passage ways.

(x)    Follow all instructions before starting any experiment.

(xi)    Wash your hands with clean water and soap after the experiment.

(xii)    Wash the apparatus and benches at the end of the experiment

(xiii)    Wear safety tools before you start the experiment

(xiv)    Read and understand all the warning signs on the container.

(xv)    Report all accidents occurred to your teacher or laboratory technician.

COMMON APPARATUS AND EQUIPMENT USED IN THE BIOLOGY

LABORATORY APPARATUS

Apparatus is a tool used for carrying out experiments in laboratory.

Some common biology laboratory apparatus and equipment include:

1.    TEST TUBE

It is used to hold, mix or heating small amounts of substance

2.    TEST TUBE HOLDER

It is used to hold test-tubes during heating

3.    TEST TUBE RACK

Used to hold and support test tubes

4.    PETRI DISH

– Used for putting specimens

– Used for growing small organisms

5.    BUNSEN BURNER

Used to heat materials in the laboratory

6.    THERMOMETER

Used to measure temperature

7.    DROPPER

◊ Used for adding liquids drop by drop

8.    BEAM BALANCE

◊ Used to measure mass of substances

9.    MORTOR AND PESTLE

◊ Used for crushing and grinding substances

10.    MICROSCOPE

Used to magnify micro-organisms

11.    HAND LENS

Used to magnify small organism/objects for observation.

12.    POOTER

Used for catching up small organisms without hurting them

It is made with two tubes where one is for sucking organisms and another for drawing in the apparatus

13.    FISH NET

Used for catching organisms living in water Example fishes and tadpoles

14. SWEEP NET

Used for catching flying insects

15. SPECIMEN BOTTLE

Used for keeping preserved organism

16. DISSECTING KIT

It carries tools used for dissection

THE MICROSCOPE

MICROSCOPE

Is an instrument used to magnify micro-organism.

Micro-organisms are very smallest organism which cannot be seen by our naked eyes.eg bacteria.

TYPES OF MICROSCOPE

There are two types of microscope

(i)    Light microscope (compound)

(ii)    Electron microscope

1. ELECTRON MICROSCOPE

Is a microscope that uses beams of electrons to magnify specimen.

The maximum useful magnification of most electrons microscope is one million times (100, 0000×)

Electron microscope is very expensive.

It is mostly found in research centres.

2. LIGHT MICROSCOPE

Is a microscope that uses light to illuminate and magnify small specimen. − Light microscope is also called compound microscope

It has low magnification compared to that of electron microscope

Maximum useful magnification of most light microscope is about one thousand time (1000×).

Light microscope is commonly found in school laboratories and health centres.

DIFFERENCES BETWEEN ELECTRON AND LIGHT MICROSCOPE

A WELL LABELLED DIAGRAM OF A LIGHT MICROSCOPE

PARTS OF THE LIGHT MICROSCOPE AND THEIR FUNCTION

Light microscope has the following parts:

(i)    Eyepiece lens (ocular lens)

(ii)    Eyepiece (ocular)

(iii)    Body tube

(iv)    Coarse adjustment knob

(v)    Fine adjustment knob

(vi)    Rotating nose piece

(vii)    Objective lens

(viii)    Stage

(ix)    Stage clip

(x)    Condenser

(xi)    Diaphragm

(xii)    Mirror

(xiii)    Arm

(xiv)    Hinge screw

(xv)    Base

HOW TO USE LIGHT MICROSCOPE

(i)    Place the microscope on the laboratory bench or table. Position the microscope such that the arm faces you and the stage faces away from you.

(ii)    Mount the specimen on slide and cover it with a cover slip.

(iii)    Make sure that the low objective lens is in line with the eye piece lens.

(iv)    Place the slide with the specimen on the stage and hold it in place with the stage clip.

(v)    While looking through the eyepiece use your hand to adjust the mirror so that the light is directed to the specimen on the stage. Always keep both eyes open when looking through eyepiece

(vi)    Adjust the coarse adjustment knob to bring the specimen into focus (vii) Adjust the fine adjustment knob to bring the specimen into a sharp focus.

(viii) Rotate the nose piece to a higher power objective lens if you want to observe more details of the specimen.

PRECAUTIONS WHEN HANDLING AND CARING OF A LIGHT MICROSCOPE

(i)    Always use two hands when carrying a light microscope. One hand holding the arm and the other holding the base.

(ii)    Never place the microscope at the edge of the bench or table. This is because it could be knocked over.

(iii)    Do not touch the surface of the mirror or lenses with your fingers.

(iv)    Clean dirty lenses using lens tissue or a soft cloth

(v)    Lubricates the moving parts regularly

(vi)    Always use the cover slip in order to protect the lenses of the microscope from getting into contact with the specimen

(vii)    Remove the slides from the stage immediately after use.

(viii)    Turn the adjustment knob slowly. Always start with the course adjustment knob.

(ix)    When not in use, cover the microscope with clean cloth and store it in dry and dustless place.

(x)    When not in use for a long time, remove the lenses and put them in a desiccator (xi) Move the objective lenses up when storing the microscope.

(xii) When storing the microscope rotate the nose piece so that the low magnification lens is in line with the eyepiece lens.

NB: SLIDE

Is a flat rectangular piece of glass used to hold a specimen for microscopic observation

SLIDE COVER (COVER SLIP)

Is a small glass used to cover the specimen on slide

MAGNIFICATION

Is the number of times the image has been enlarged

– In microscope, magnification is determined (calculated) by multiplying the eye piece lens magnification by the objective lens magnification.

Worked Example

1. Calculate the total magnification of the image seen by ×5 of eyepiece lens and by ×10 of the objective lenses

Solution

Data given

Total magnification =Asked

Eyepiece lens magnification = 5

Objective lens magnification =10

Total magnification = eyepiece lens magnification × objective lens magnification

Total magnification = 5 ×10 =50

Therefore, the total magnification of the image is ×50

2. Calculate the objective lens magnification of the object, if the total magnification is ×250 and the eyepiece lens is ×10

Solution

Data given

Total magnification =250

Eyepiece lens magnification = 10

Objective lens magnification =Asked

From:

Total magnification = eyepiece lens magnification × objective lens magnification

250 = 10 × objective lens magnification

Objective lens magnification = = 25

Therefore, the objective lens magnification is ×25

REVISION QUESTIONS

1. Calculate the total magnification of image, if the objective lens magnification is ×20 and eyepiece lens magnification lens is ×10.

2. If the magnification power of eyepiece lens of a compound microscope is ×10 and that of the high-power objective lens is ×50, what is the total magnification of the specimen under observation?

3. Calculate the objective lens magnification of object. If the total magnification of the object is ×300 and the eyepiece lens magnification is ×5.

4. Calculate the eyepiece lens magnification of an object. If the objective lens magnification of the object is ×15 and the total magnification of an object is ×120.

HAND LENS

Is an instrument composed of a convex lens used for magnifying small objects.

The Diagram of hand lens

PARTS OF HAND LENS

Hand lens has three main parts, namely:

(i) Convex lens: used for magnifying small objects.

(ii) Frame: gives support to the convex lens

(iii)Handle: helps to handle the hand lens when moving it.

HOW TO USE A HANDLENS

In order to magnify an object by using a hand lens, the following procedures should be followed:

(i)    Place the object or specimen under observation on the bench or table.

(ii)    Move the hand lens with one hand from the object or specimen to the eye

(iii)As the object or specimen comes into focus an enlarged image will be observed

How to determine magnification of an object or specimen viewed under a hand lens Magnification of an object or specimen viewed under a hand lens is determined (calculated) by dividing the length of a drawing by the length of the actual object. As follows:

𝐋𝐞𝐧𝐠𝐭𝐡 𝐨𝐟 𝐚 𝐝𝐫𝐚𝐰𝐢𝐧𝐠(𝐢𝐦𝐚𝐠𝐞)

Drawing magnification =

𝐋𝐞𝐧𝐠𝐭𝐡 𝐨𝐟 𝐭𝐡𝐞 𝐚𝐜𝐭𝐮𝐚𝐥
𝐨𝐛𝐣𝐞𝐜𝐭

OR

𝐒𝐢𝐳𝐞 𝐨𝐟 𝐚 𝐝𝐫𝐚𝐰𝐢𝐧𝐠(𝐢𝐦𝐚𝐠𝐞)

Magnification of a drawing =

𝐒𝐢𝐳𝐞 𝐨𝐟 𝐭𝐡𝐞 𝐚𝐜𝐭𝐮𝐚𝐥 𝐨𝐛𝐣𝐞𝐜𝐭

WORKED EXAMPLES

1. A drawing of 10cm in length was made of Bee of 5cm in length. Calculate the magnification of drawing.

Solution

Data given

Length of a drawing =10

Length of the actual object = 5

Magnification of a drawing =Asked

From:

Length of a drawing

Magnification of a drawing =

Length of the actual object

10cm Magnification of a drawing = = 2

5cm

Therefore, Magnification of a drawing is ×2

REVISION QUESTIONS

1.    If the length of the drawing is 8cm and the actual length of the object is 2cm. What will be the magnification of a drawing?

2.    (a)How do you determine the magnification of an object viewed under a hand lens?

3.    Basically, there are two types of microscope, name them:

4.    Compare and contrast a light microscope and an electron microscope.

5.    How do you determine the magnification of an object viewed under a light microscope

6.    Mention three parts of a hand lens

7.    (a) Draw a well labelled diagram of a light microscope.

(b) State the function of each part labelled in the diagram 7 (a) above.

8.    Draw a well labelled diagram of a hand lens.

The following are warning signs that are found on apparatus and chemical containers in the laboratory or on the boxes in which chemicals and apparatus are kept.

(i)    Toxic

(ii)    Corrosive

(iii)    Flammable

(iv)    Oxidant

(v)    Explosive

(vi) Harmful

(vii) Irritant

(viii)    Fragile

(ix)    Radioactive

(x)    Biohazard

1.    TOXIC

Is a poison substance which may cause death when touched, swallowed or inhaled.

Examples of toxic substances

– Pesticides

– medicine

A diagram of toxic warning sign

2.    CORROSIVE

Is a substance that can burn the skin or a surface.

= It can cause body wounds or burn various things such as a clothes and furniture

Examples of corrosive substances

– Concentrated acids e.g. sulphuric acid,

– Concentrated alkaline e.g. Sodium hydroxide.

A diagram of corrosive warning sign

3.    FLAMMABLE

Is a substance which can catch fire easily.

– The substances should never be brought near open flame

Examples of flammable materials

– Alcohol

– Petrol

– Kerosene

– Diesel

A diagram of flammable warning sign

4. OXIDANT

These are chemical that can accelerate burning of materials.

Example of oxidant substances

– Potassium permanganate

– Potassium hydroxide

A diagram of oxidant warning sign

5. EXPLOSIVE

An explosion is a forceful rapid reaction, which involves throwing off of particles at high speed.

Example of explosive substances

– Gunpowder

– Mosquito spray

6. HARMFUL

Is the substance which can cause illness.

This substance may not kill immediately but may have effects when used for a long period.

Examples of harmful substances

-Alcohol

– Cigarettes

DIAGRAM OF HARMFUL

7. RADIOACTIVE

Is the substance that emits harmful radiations.

– Radioactive substances are elements that emit radiations either alpha, beta, gamma or neutrons.

– Radioactive substances can cause dangerous effects such as skin damage, skin diseases, disabilities, death, blindness and various types of cancer ases Example of radioactive

– X- rays

– Uranium splits to emit neurons

– Radium emits alpha and gamma rays

– Tritium emit beta rays

– Cesium emit gamma rays

A diagram of radioactive warning sign

BIOHAZARD

Is a biological substance that can cause disease or threat to the health of humans.

– Biohazard contains microbes

– Biohazard is a short form of biological hazard

Example of biohazards substances

– Medical waste e.g. wound dressings

– Sludge waste