Biology Form One Notes – Introduction to Biology

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TOPIC ONE

INTRODUCTION TO BIOLOGY

Basic Concepts and Terminologies of Biology

Biology

Biology is derived from two Greck words, that is, bios which means life

and logos ot logia which means study or knowledge.

So biology can be defined as a branch of science which deals with the study of life. The term

biology ean also be defined as a branch of science which deals with the study of living things or

organisms

Biologist

A person specialized inthe study of biology

Life

Life means being alive or existing, Something is alive or existing if it possesses life processes.

The life processes are growth, movement or locomotion, respiration, excretion, reproduction,

sensitivity and nutrition

Organism

Organism is anything which has life. Its the other name ofa living thing. Organisms are made

up of cells

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A cell is a basic unit of living things. The cell has three main parts, cell

‘membrane, cytoplasm and nucleus. Cells which make up plants are called plant cells and those

Which make up animals are called animal cells.

Some organisms are made up of one cell. They ate called unicellular or single-celled organisms

eg, amoeba, euglena and yeast. Some organisms are made up of many cells, they are called

‘multi cellular organisms e.g. animals, plants, and most fungi.

“The Characteristics of Living Things

(Outline the characteristics of living things

View Teacher Notes

Movement/locomotion

All iving organisms are capable of movement. Movement is the change of position ofthe whole

‘organism or just part of an organism, For animals and unicellular organisms the movement is of

the whole body. This is known as locomotion. Most animals move about using legs, wings or

fins. Unicellular organisms such as amoeba, paramecium and euglena use the locomotory

structures pseudopodia, cilia and flagella respectively.

In plants only part of it may move towards different factors suchas light, water, gravity tc, They

move by growing, Their roots grow down in the soil and their shoots grow up into the air or

towards a source of light.

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Irritability (sensitivity)

Invitability isthe ability of an organism to respond to a stimulus. Stimulus (plural; stimuli) is

anything that causes a response in an organism,

‘Examples of stimuli include: an alarm clock, a smell of breakfast cooking and a fly landing on

your skin.

All living things are sensitive to certain changes in their surroundings, tat is, they are aware of

‘what is happening around them. This is possible because they have special organs known as

sense organs by which they detect these changes.

[Examples of sense organs include: eyes for vision (sight); skin for temperature, touch, pressure

<etection; rongue for tating; nose for smelling, and ears for hearing and body balance.

Plants do not have sense organs but are still able to detect and respond to things like gravity,

water and light

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Feeding (Nutrition)

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

health

Animals get their food by eating other living things or food materials that were once living

things. Herbivores (eg rabbits) eat plants, carnivores (e.g. lions) eat other animals, and

‘omnivores (e.g. humans) eat animals and plants. Pants make their own food through the process

called photosynthesis.

‘The process of taking in food, synthesizing i, digesting and oxidizing it to release energy of

build the body is called nutrition,

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Respiration

Respiration is the breaking down of food materials within cll to release enerny

Respiration usually involves the use of oxygen. All living things need eneray for movement,

growth and development, and funetioning of body organs.

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Excretion

All living things produce wastes such as carbon dioxide, water, urea, ammonia ete. Some of

these chemicals if left to accumulate in the cells would seriously poison the living organism

hhence they need to be removed, The process of removing metabolic waste products from the

body of living organisms is called excretion.

Waste products are removed ftom the body by excretory organs such skin, kidneys, lungs and

liver.

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Reproduction

Reproduction isthe process by which living things produce new individuals of their own kind.

All iving things reproduce, to replace organisms lost by death. Ifa group of organisms does not

reproduce fast enough to replace those which die, the group becomes extinct. Reproduction

{ensures continuation of life when parent generation dies

‘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.

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They respire Do not spire

They grow Do not grow

“They respond to stimuli ‘Do not respond to stimuli

They reproduce Do not reproduce

‘They excrete Do not excrete

They feed Do not feed

‘They move Do not move

Branches of biology

Biology isa subject and it has many branches. The main branches

are botany and zoology:Botany is a branch of biology which deals with the study of plants. A

person who studies botany is called a botanist. Zoology isa branch of biology which deals with

the study of animals. A person who studies zoology is called a Zoologist

Other branches of biology

“Mycology: ths isthe study of fungi. A person who studies mycology is called a mycologist

Bacteriology: this is the study of bacteria. A person who studies bacteriology is called

a bacteriologist.

Virology: this branch of biology deals with the study of viruses. A person who studies virology

is called a virologist.

Immunology: is concemed with body defense against diseases and foreign substances. A person

‘who studies immunology is called an immunologist

Entomology: refers to the study of insects A person who studies entomology is called

an entomologist.

Parasitology: this branch deals with study of parasites and ther effects on living organisms. A

person who studies parasitology i called a parasitlogist.

Dermatology: It is concerned with medical study of skin and its diseases. A person who studies

dermatology is called a dermatologist

Ecology: I a branch of biology that deals with relationship among living things and between

‘organisms and ther surroundings. A person who studies ecology i called an ecologist

‘Amatomy: Is the study which deals with structure of living things. A person who studies

anatomy i called anatomist

Diagram representing branches of Biology

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Endocrinology: This isthe study of structure of endocrine glands and the hormones associated

by them. A person who studies endocrinology is called an endocrinologist

Histology: Is the study of structure of tissues A person who studies histology is called

an histologist

Cytology: Is the study of structure, composition and function of cells. A person who studies

eytology is called a cyologis.

Microbiology: Is devoted to the study of organisms that can be seen only with a microscope e.g

bacteria, viruses, some fungi and some protoctists. A person who studies microbiology is called a

microbiologist.

Taxonomy: Is the scientific classification of organisms. A person who studies taxonomy is

called a taxonomist.

Genetics: Study of heredity and variation in organisms. A person who studies genetics is

called geneticist

‘The Importance of Studying Biology

The study of biology is very important to man.

‘The following isan outlines of why the study of biology is important:

1. Ithelps us to understand ourselves better since we are living things.

2. Skills and knowledge of biology can be applied to other scientific fields such as agriculture,

‘forestry medicine, nutrition, pharmacy and veterinary science,

3. Ithelps us to understand our environment better and principles of conserving it

‘4. Biology helps to answer some important questions such as, what do living things need, why do

\ve resemble with a monkey, why do ffogs lay many eggs but only few become adults?

5. Knowledge of biology helps us to improve our health since eauses, symptoms, transmission and

treatment are of various diseases are studied in biology.

6. Knowledge of biology helps us to avoid our selves from magical beliefs, superstitions and other

traditional taboos.

7. Knowledge of genetics helps us to clear some common doubts about certain inherited

characteristics eg. albinism, sickle cell anaemia, haemophilia ete

8. Knowledge of the structure and chemical composition of the organisms enable us to acquire

ood, clothes and shelter ffom them,

Relationship between Biological Science with other Related Fields

‘Veterinary science (Veterinary medicine)

‘Veterinary medicine isthe branch of medicine that deals withthe diseases of animals. Doctors

that treat animals are called Veterinarians. Veterinarians are trained to prevent, diagnose and

treat illness in large and small animals. Their work is valuable because many animal diseases can

be transmitted to human beings e.g. rabies, tuberculosis, tularemia (rabbit fever) anthrax ete

Basic knowledge of biology is required for successful study of veterinary science,

Agriculture

Agriculture is concerned with production of useful plants and animals through farming system.

Agriculture provides us with almost all our food. It provides materials for clothing and shelter. It

provides materials used for making many industrial products such as paints and medicines.

Agriculture uses knowledge of biology to improve plant and animal breeding. Genetically

‘modified organisms (GMOs) ensure beter quality early maturity and high yield products. Crop

and animal diseases and pests can only be overcome by applying biological knowledge.

Forestry

A forest isa large area of land covered with trees. Is much more than just trees. It also includes

smaller plants such as mosses, shrubs and wild flowers. Forestry is the science of managing

forest resources for human benefit. The practice of forestry helps maintain an adequate supply of

timber and management of such valuable forest resources such as water, wildlife, grazing areas

and recreational areas,

Biology helps in improving the qualities of the trees through manipulating the genetic

‘constitution ofthe particular plant species.

Climate, soil and water determine the type of plants to be grown which entirely applies

biological knowledge. Use of biological control to combat tree pests applies biological

principles.

Pharmacy

Pharmacy is the profession concerned with the preparation, distribution and use of drugs.

Members of this profession are called pharmacists or druggists. Pharmacy also refers toa place

‘where drugs are prepared or sold The drugs are made depending on the chemical composition of|

the body of an organism and how they can react with such medicines. Knowledge of biology also

helps to know the effects of drugs on living things (pharmacology) and possible remedies to be

taken

Medicine

Medicine isthe science and art of preserving health and treating illness. Medicine is a science

because itis based on knowledge gained through careful study and experimentation. It isan art

because its success depends on how skilfully medical practitioners apply their knowledge in

<ealing with patients. The goal of medicine include saving lives, relieving suffering and

‘maintaining the dignity of sick people. Biological knowledge helps the doctors, surgcons and

‘nurses to diagnose, treat and prescribe the right medicine to cure the disease.

Biological knowledge will also help them to offer education to the patients on how to prevent

themselves from the diseases e.g. purifying drinking water, vaccination against polio, measles

and other diseases

Nateition

[Ntrtion is the science which deals with food and how the body uses it. People, lik all living

things need food to live. Food provides substances that the body needs to build and repair its

tissues and to regulate its organs and systems. Food also supplies energy for every action we

perform. Knowledge of biology helps to identify the type of food required by an individual based

on its quality and quantity

A table showing differences between plants and animals

PLANTS ANIMALS.

(They are autotrophic, ie. they can make their own They are heterotrophic ie. they feed on complex

food ‘organic compounds

(Gi)Contain chlorophyll, can undergo photosynthesis. No chlorophyll, cannot undergo photosynthesis

(Gil]Growth occurs in some parts only ie. root and

iowth occurs in all parts ofthe

Shootin Growth pars of the body.

(iv) They have branched bodies ‘They have compact bodies

(W)No nerves, muscles, blood system or special sensory Have nerves, muscles, blood system and special

cells sensory cells

(vi)Usualy rooted in the ground and do not move from Not rooted in the ground, move to get food and eseape

place to place. enemics.

(vilHave no digestive system Have digestive system needed to break down food.

(vi)Cells of plants have cell walls Cells oF animals have no cell walls

Scientific Processes in Biology

Biology, just like other science subjects, involves carrying out experiments. When studying

living things simple observation can be made by using our own senses ie. sight, smell, ouch,

taste and hearing, The senses can be detected by our sense organs ie. eye for sight, nose for

smell, skin for touch, tongue for taste and ear for hearing,

To Use Own Sense Organs to Make Correct Observations

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Measurements of Mass, Length, Temperature and Pulse Rate

Measurements: When carrying out biological investigation measurements like mass, time,

temperature, and length are unavoidable

Instruments used for various measurement:

Beam balance ~ for measuring mass

. Thermometcr~ for measuring temperature

18. Ruler ~for measuring length

Pulse rate can be measured by sing a stethoscope or by pressing the fingers Firmly on the skin.

‘The study of biology lke any the science subject involves scientific processes. The scientific

processes involved in the study of biology

include observation, measurement and experimentation, Through these proceses the study of|

biology becomes possible

OBSERVATION

‘Through observation we can lar many scientific phenomena. Observation is made by using our

cown sense organs. There are ive sense organs in the human body which are eyes, eas, the nose,

the tongue, and the skin. Each of these organ is specific toa certain type of observation

‘The following are sense organs and their associated fanctons in observation.

Eyes

How can you differentiate between the colors ofan eng from that ofa ripe pawpaw? In this case

in onder to answer this question coretly, you must be able to make corect observation. By

using your eyes you can observe differences in colors of the two things given and then tel thee

differences.

We use our eyes as a sense organ for vision. By using our eyes we are able 1o see and

Aire sizes, colours and shapes of various organisms and hence we ean learn about them.

Fars

ow can you distinguish between the sound produced by a singing bird and a roaring lion?

Sometimes you can just use your eas to study various biological concepts. For example many

organisms produce different sounds which we ean use to identify them.

‘Therefor, itis easy fora biologist to know an organism jut by hearing the sound without even

seeing it This proves how your ears are very important organs in scientific studies because they

ae used to identify and differentiate sounds of varios living organisms.

Nose

Sometimes inthe scientific study we need to smell in order to identify and distinguish between

‘various things. For example, how ean you distinguish the smell ofa ripe banana from that of a

ripe pineapple? As a scientist you must beable to use your nose as a sense organ effectively and

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ato things Some ofthe quantities which can successly be mesued include mas,

‘temperature, length and pulse rate,

Measurement of ngth

We can use ees observe the leg of varios abo However ou ys can ju el which

bj i ng tan the eer but can ntl us what he exact length ofeach bjt. Tape

‘measure is one of the common instruments that are used for measuring length in our every day

Tape measue,an instrument for measuring length

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Measurement of mass

A sist of bislogst must havea sandard way of measuring mass of @subsance. Sense

cxzans camo give us the tue vale of mss of substance. This can be done by sing beam

balnce which isa sei instrument for measuring mas of substance

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|In our day to day life we often come across questions or phenomena which require explanations.

Such questions or phenomena are of interest to a biologist who will seek to provide answers to

them,

The phenomena could be for example; it was observed that the harvest of tomatoes in Juma’s

‘garden was low despite frequent irrigation, correct planting techniques, timely planting and

adequate sunlight. So, what was the problem with Juma’s garden?

Tis is the problem to be investigated by the biologist in order to come up with an answer.

Hypothesis formulation

Hypothesis isa tentative explanation forthe observation made. Using your example of low yield

inthe tomato garden, the possible hypothesis could be poor yield could have been caused by low

soil fertility and therefore application ofthe fertilizer could increase harvest ofthe tomatoes in

the garden. This hypothesis must therefore be tested by experimentation if it has to be a

scientifically acceptable explanation

Experimentation

‘An experiment is series of investigation intended to discover relationship or certain facts that

‘may lead to finding a problem. In the ease of low harvest of tomatoes, you are first supposed to

construct plan of investigation as follows

Select two plots, A and B, from the same garden and subject both of them tothe same conditions

as before. In plot B apply fertilizers while in plot A don’t put any fertilizers (plot A will be your

control plot).

Observation and data recording

‘After setting up an experiment, a researcher must observe and record data, Observation is done

by using sense organs such as eas, eyes, nose and skin. The researcher must record whatever he

observes. The researcher obtained X kg in plot A and Y kg in plot B.

Interpretation of data

Once a researcher has collected data, he should try to explain the meaning of data in relation to

the purpose ofthe experiment. Inthe tomato garden experiment, the harvest in plot A was litle

‘compared to the harvest in plot B.

In these plots, all the conditions were the same except that in plot A no fertilizers were applied

‘hile in plot B fertilizers were applied. Therefor, high harvest in plot B was a result of applying

fertilizers. If this experimentation is correct, then the same results should be obtained if the

experiment is repeated under the same conditions.

Conclusion

At the end of investigation, a researcher must draw conclusion. This conclusion is based on the

collected data, The conclusion is cither confirmation or rejection of the hypothesis under

investigation

In the tomato garden experiment, the results have shown that application of fertilizers has

increased the harvest of tomatoes. Therefore, low harvest of tomatoes was caused by poor soil

fertility,

Summary

The following diagram summarizes the scientific process.

“The scientific process

——

The Biology Laboratory

Describe the biology laboratory

Abiology laborntory is a room or building specially designd for carying out biological

experiments

biology laboratory has

1. Lage windows and big space to allow enough si and light fr beter ventilation and visility

respectively

2._ Shelves for keeping chemicals, specimens appara nd modes

3. Suply ofa clecticty and water

4. Working benches

5. Am emergence door in case of anger occurs.

6, Preparation rom

‘The biology laboratory rales

Biology laboratory has sophisticated instruments which need to be handled with special cae.

Chemicals which are being used are potentially harm and they need a special tention when

vworking with them

The following laboratory ules shouldbe adhered to:

1, Dont ener inthe laboratory without permission fromthe teacher or laboratory tecrician

2. Domnot play, or run unnecessarily inthe laboratory.

3. Domnot ea or drinkin the laboratory.

4 Do not use chemicals or handle apparatus or specimens without instruction from the teacher or

Inhoratory technician

5. Any acidet or damage of epparats must be reported

6 Label chemicals and specimens to avoid conision.

7. Always keep flammable substances away from flames.

8. Tur off water and gs taps afer we

9 Never point the open end ofthe test tbe to your fellow or yourself when heating

10, Never smell substances specimens, chemical or gases dict

11, Wash your hands with soap afer the experiment

12, Clean the apparatus and benches after the experiment

13, Retun the apparatus and chemicals to their normal positon afer use

‘The Difernce between the Biology Laboratory fom othr Schoo! Facilities

Distinguish the biology laboratory from other schol facilities

Difference between biology laboratory and other school facilites:

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+ Models of different organs and systems

+ Refiigerators and ovens for storing and drying specimens

+ Animal keeping units

+ Chemicals designed for biological experiments

+ Preserved specimens of living things

+ Gases, electricity and water supply.

Aim: To differentiate biology laboratory from other school laboratories or facilities

Procedure: let students visit the chemistry laboratory, physics laboratory, the school library,

classroom and school store and allow them to perform the following,

| Make alist of items that are found in each ofthe above named areas.

2. Compare the list with those which are found in the biology laboratory.

3. Construct a table of differences showing a list of tems which are found in the biology laboratory

and those which are found inthe above named school facilities as shown below:

4. List items which are found in both the biology laboratory and other school facilites listed above

and compare the differences.

Facility / Building tems

Biology laboratory

‘Chemistry laboratory

Physies laboratory

School library

Classroom

School store

Interpretation of Warning Signs on Containers of Laboratory Chemicals and Apparatus

{Interpret warning signs on containers of laboratory chemicals and apparatus

‘Warning signs on laboratory chemicals and apparatus,

‘Some of the chemicals and apparatus used in biology laboratory may be harmful or dangerous

Before stating using any chemical you must know whether the chemical is toxic, flammable,

oxidizing, explosive or irrtanvharmful. To help you recognize such dangerous substances, the

containers of modern chemicals carry special chemical warning signs as indicated below.

Toxie

Toxic substances can cause death. They may be poisonous when swallowed, breathed in or

absorbed through the skin. Examples of toxic substances include acids and alkalis, lead Il acetate

and potassium dichromate.

‘The symbol for toxic substances is represented as shown above.

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Flammable

Flammable substances are substances which can catch fire easly. Examples of such substances

include petrol, alcohol, Thomas Baker (Phosphorus yellow or phosphorus red) and potassium

metal, These substances normally evaporate fast and therefore should not be brought near open

‘ames. The symbol is as indicated above.

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‘

Corrosive

Oxidant

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into contact with the skin or eyes for too long. Examples of harmful substances include lead

chloride, lead nitrate, lime water ferrous sulphate and manganese (IV) oxide

Examples above of some chemical containers with their warning signs.

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containers Procedure: collect chemical containers. Observe them carefully and identify chemical

Record your results as shown in the table tha follows

Chemical container Warning sign

‘The Common Apparatus and Equipment of Biology Laboratory

Some apparatus and equipment used in the biology laboratory.

1. Microscopes

2. Hand lenses

3, Thermometers

4. Dissecting its

5. Mortar and peste

6. Dissecting rays

1. Delivery tubes

8. Measuring cylinders

9. Bunsen burners

10 Test tubes

11, Specimen bottles

12. Ovens

13. pair of scissors

14, Chemical balance

15. Funnel

16, Test tube racks

17 Test tube holders

18, Beakers

19. Forceps

20, Surgical blades

21, Microscope sides

22. Droppers

25. Spatula

24, Corks

25. Glass straws

27, Mounted needle

28. Beam balances

29, Gass rods

30. Scalpels

Microscope

Thermometers

Hand lenses

Dissecting kit

“Motor and Pestle

Dissecting tray

Delivery tube

“Measuring eylinder

‘Specimen Bottles

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Oven

Pair of scissors

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Spatula

Cork

Giass straws

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‘Beam balance

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Sealpels

Dropping pipete

Fridge’refrigerator

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‘Some common chemicals used in the biology laboratory

+ Benedict’ solution

+ Lime water (calcium hydroxide)

+ Sodium hycroxide (slaked lime)

+ Cobalt chloride

+ Hydrochloric acid

+ Copper (It) sulphate

+ Sudan I

+ Alcohol

+ Stains eg carmine red, methylene blue

+ Sodium bicarbonate

+ Potassium permanganate

+ Iodine solution

In each of the following questions write TRUE for correct statement and FALSE for incorrect

statement

a A biology laboratory isa place where biological experiments are

conducted

b, Everything in the laboratory can be tasted

c. Waming signs can help someone to avoid accident’ inthe

laboratory

(One of the following is not a basic quality ofthe biology laboratory.

a Working benches

. Large windows and big space

‘Supply of gas, electricity and water

Kitchen

‘Substances which may catch fire easily are said to be

a. Toxic

b. Flammable

Explosive

4. Irritant

‘An instrument used to measure temperature of the body is called

‘4. Chemical balance

b. Measuring cylinder

‘¢. Thermometer

4. Barometer

(One of the following is a common reagent used inthe biology laboratory

1. Benedict’s solution

b. Potassium iodide

Sodium acetate

4. Barium chloride

Which ofthe following list of instruments is not related to biology laboratory?

a. Fridge, a pair of scissors, surgical blades

b.. Microscope, test tube, thermometer

‘Dissecting kit, sealpel, beaker

‘4. Meter bridge, pendulum bob and burete

‘The waming sign shown indicates

a. Explosive substance

b. Oxidizing agent

‘¢. Flammable substance

4d. Corrosive substance

LIST A

List B

b. Oxidant

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What do you understand by the following terms?

Draw warning signs which may be used in bottles carrying a substance which is

a. toxic

b. flammable

explosive

harmful

List down any six (6) laboratory rules

State the use ofthe following apparatus

a. Specimen bottles,

b. ‘Test tube holders

‘¢.Beam balance

4. Beaker

raw the following apparatus:

a Measuring cylinder

b. Mortar and pestle

e. Funnel

Tripod stand.

‘THE MICROSCOPE

“Mach of the living world is too small for human eyes to see. Our eyes ean only see objects that

are larger than O.Imm. Objects with sizes smaller than 0.1mm can be viewed by using

microscopes.

What isa microscope?

‘A microscope is an instrument used for viewing objects which are too small to be seen by our

naked eyes, It ranks as one ofthe most important tools of science,

‘+ Physicians and biologists for example, use microscopes to examine bacteria and blood cells,

‘+ Material scientists and engineers use microscopes to study the crystal structures within metals

and alloys (metal mixtures) and to examine computer chips and other tiny electronic devices.

‘There are two types of microscopes

Compound oF light microscope

». Electron microscope

Optical oF light microscope

‘An optical microscope has one or more lenses that refract (bend) the light rays that shine through

oF are reflected by the specimen being observed. The refracted light rays make the specimen

appear much larger than its

Magnifying glass isthe simplest optical microscope, has only one lens. The best magnifying

lasses can magnify an object by 10 to 20 times,

‘The compound or light microscope

‘The compound or light microscope uses two or more sels of lenses to provide higher

‘magnifications. Each set of lenses functions as a unit and is referred to as lens system. In

‘microscopes with only one objective, the lens system and ocular are mounted at opposite ends of

tube. In microscopes with two or more objectives the objectives are mounted ina rotating nose

piece connecting o the end ofthe tube opposite the ocular. The person operating the microscope

rotates the nose piece to align one ofthe objectives with the opening in the end of the tube

The workings of electron and compound microscope Electron microscope ~ Uses electrons to

illuminate the specimen and can reveal much more structures than light microscope can do.

Light microscope – Uses light to illuminate the specimen

Parts ofthe light microscope and their functions

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Parts of the light microscope has the following functions:

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3. Revolving nose piece — Holds objective lenses in place. Position of the objective lenses can be

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12. Base or stand ~ Supports the microscope steadily

13. drm or limb ~ Supports the body tube and stage. Itis used to hold the microscope

14, Hinge screw ~ Raises and lowers the tage

Magnification

Magnification power is symbolized by a number and abbreviation X. For example a 10X

magnifying glass magnifies an object by 10 times. An object is magnified by multiplying the

eyepiece lens magnification and objective lens magnification,

Example:

“Magnification = eyepiece lens x objective lens magnification

= 10 20 x20

A table of magnification

ye piece lens magnification (Objective lens magnification Total magnification

5 2 X100

10 2» x20

1s 10 x150

10 2s 250

2» 2» 400

How to use a microscope

1. Tum on your microscope light

2. ‘Tum the nose piece so thatthe small (low power) objective lens clicks into place. Always stat

with low power lens in place.

3. Place the prepared slide on the center of the stage under the clips so that the object is in the

center of the opening. Make sue the cover slp is ontop

4. With your eye at stage level, use the coarse adjustment to bring the object and the low power

objective lens as near to each other as possible. The objective lens should not touch the coverslip

5. Now with your eye to the eyepiece, slowly move the coarse adjustment to increase the distance

‘between the object and the lens. Continue this until the image is Focused,

6. Adjust the diaphragm so thatthe object can be seen as clearly a possible

7. To observe the object under medium and high powers, rotate the revolving nose piece to bring

the next highest objective lens into position. Make sure you hear the ‘click’ to ensure thatthe

objective lens isin place. Then, focus using the fine adjustment only

‘Ways of handling and carrying light microscope

1 Use both hands to carry the microscope. One hand should hold the base and the other hand

should hold the arm.

b. Always place the microscope on the desk or table carefully and gently and never place it atthe

edge ofthe bench

‘c. Keep the microscope in an upright position when using liquids or when notin use.

4d. Keep the stage clean and dry. If any liquids are spilled on the microscope, wipe them up

immediately with apiece of tissue.

«Focus withthe low-power objective lens frst,

Focus by moving the lens away from the slide, that is, by increasing the working distance,

8 Consult your teacher ifthe lenses are dirt.(vit) Consult your teacher ifthe adjustments do not

work freely.

When your work is completed, move the low power objective lens into place and remove your

slide.

i. Keep your microscope covered when its not in use and keep your work area clean and tidy.

ELECTRON MICROSCOPE,

This type of microscope uses a beam of electrons rather than a beam of light to produce

‘magnified images. Electron wave lengths are much shorter than those of visible light. As a result

clectron microscopes can resolve much finer detail than light microscope can do,

\——s

Electron microscope

Types of electron microscopes

a Transmission electron microscope (TEM) This type of a microscope passes a broad beam of

clectrons through a specimen slice a few hundred angstroms thick.

b. Scanning electron microscope (SE M) This microscope seans a focused beam across the surface

ofthe specimen

Other kinds of microscopes

‘Scanning probe microscope The microscope scans a specimen with a sharp point called a probe

The ion microscope (field -ion microscope) I’s used to examine metals. It creates an image of

the crystal structure of the tip ofan extremely sharp metal needle. An electri field applied tothe

tip repels charged helium, neon or argon atoms which spread out and strike a special sereen. The

soreen glows where the atoms strike it, forming an image of the arrangement of atoms in the

metal

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