Scientific investigation of the environment

Created by Tharaka Dilshan

(B.Tech civil engineering)

Scientific Method to solve the problem

Observations

The problem

assumptions or hypothesesexperiments

Analyzing the experimental data

and get a conclusion

What is control experiment?• when designing an experiment to test a hypothesis it is necessary to

do a second test in addition to the first experiment. In the second experiment all the factors except the variable factor that is under investigation are kept constant.

The Theory Of SpontaneousGeneration

Discovery of Penicillin• What is penicilline

lexander Fleming, a doctor by profession, involved in an experiment on disease causing bacteria. During the experiment, he observed that the bacteria has got destroyed in some of the bacterial cultures prepared by him. Fleming developed a hypothesis on the above observation, carried out several experiments to test the hypothesis and finally came up with a ground braking discovery. His discovery was that a fungus that has entered the bacterial culture accidentally, secreted a chemical substance that destroyed the bacteria. This secretion is the antibiotic Penicillin secreted by the fungus Penicillium. Today it is an essential antibiotic in the field of medicine.

Self assessment• Where can we use scientific method in day-to-day life?• Do following experiments and state steps under scientific method?

1. Photosynthesis need sun light2. Egg is drawn in a salt water.3. Iron transfer heat by conduction.

Observe minute objects• Minute objects? Small object that are not visible to naked eye.• What are minute objects?

1. Cell2. Micro organism 3. Small letters in currency note4. What apparatus that can be use to see them

optical microscope• Simple microscope (Convex lens/Magnifying lens)• Compound Microscope• Optical Microscope / Light Microscope

Simple microscope (Convex lens/Magnifying lens)

Principle of Simple Microscope• A simple microscope works on the principle that when a tiny object is

placed within its focus, a virtual, erect and magnified image of the object is formed at the least distance of distinct vision from the eye held close to the lens.

• According to the above observation, it is concluded that the distance between the convex lens and the object is an important parameter to get a clear image with maximum magnification

Uses of Simple Microscope• Following are the important uses of simple microscope:

• The simple microscope is commonly used by watch makers to see the magnified view of small parts of a watch.

• It is also used by the jewelers to see the magnified view of the fine parts of jewellery.

• Simple microscope is used to see the enlarged image of letters of a book, textures of fibers or threads of a cloth.

• Simple microscope is used to see the magnified view of different particles of different types of soils.

• It is used by palmists to see enlarged view of the lines of our hand.

• Simple microscope is used by skin specialists to find out various diseases of skin.

• It is also used to see the details of stamp and engravings.

Compound Microscope

The lens kept closer to the eye is called the eye piece, and the lens kept close to the object is called the objective. To obtain a highly magnified image using two lenses with different curvatures, you should use the lens with the lesser curvature as the eye piece and the lens with the

greater curvature as the objective.You may have experienced the problems given below in doing activity• Difficulty in placing the two lenses on the same line.• Image get curved and appear coloured near the edges of the mirror.• Difficulty in getting the fine adjustment of the lenses

Optical Microscope / Light Microscope

Principle of compound microscope• A compound microscope works on the principle that when a tiny

object to be magnified is placed just beyond the focus of its objective lens, a virtual, inverted and highly magnified image of the object is formed at the least distance of distinct vision from the eye held close to the eye piece.

Construction of compound microscope•  A compound microscope consists of two convex lenses: an objective

lens O of small aperture and an eye piece E of large aperture. The lens which is placed towards the object is called objective lens, while the lens which is towards our eye is called eye piece. These two convex lenses i.e. the objective and the eye piece have short focal length and are fitted at the free ends of two sliding tubes at a suitable distance from each other. Although the focal length of both the objective lens and eye piece is short, but the focal length of the objective lens O is a little shorter than that of the eye piece E.        The reason for using the eye piece of large focal length and large aperture in a compound microscope is, so that it may receive more light rays from the object to be magnified and form a bright image

In handling an optical microscope it is important to follow the instructions given below• Before observing any object under the the microscope, place the

microscope on• a flat table or surface and adjust the objective with the lowest

magnification in line• with the optical tube.• • Place the microscope in a place having strong sunlight or an artificial

source of• light. (Ensure that direct sunlight does not fall on the mirror.)• • Observe through the eyepiece and adjust the lens to get maximum light.• • Mount the specimen on a glass slide and cover it with a coverslip.• • Place the prepared slide over the aperture on the stage of the microscope

and fix• it with the clips.• • Observe through the eyepiece and adjust the optical tube carefully till an

image is• seen.• • Make use of the fine adjustment and get a clear image. (When observing

it is• better to use the fine adjustment. The right hand can be used to make

adjustments• while the specimen can be observed through the left eye. It is important to

keep• both eyes open when you observe.)• • After observing, take the optical tube upwards using the coarse

adjustment.• • Remove the specimen, and wipe the lenses and stage with a dry cotton

cloth.• • When carrying the microscope from one place to another, keep its base

on the• palm of the hand, and handle it firmly at its arm.• • To provide a dust free environment, cover the microscope with a plastic

cover• and keep inside a wooden box.• • If the microscope has to be stored for a long time without using , the

objective• lenses and eye pieces shoud be removed and place them in a decsicator

containing• a dehydrant such as calcium chloride or silica gel.

Differences between Simple Microscope and Compound Microscope

S No. Simple Microscope Compound Microscope

1.A simple microscope is also called magnifying glass. It is actually a convex lens of small focal length, which is used for seeing the magnified images of small objects.

A compound microscope is an optical instrument consisting of two convex lenses of short focal lengths which is used for observing the highly magnified images of tiny objects.

2. It consists of one convex lens. It consists of two convex lenses of short focal length.

3. Its maximum magnifying power is 10. Its maximum magnifying power is 1000.

Examples

Self assessment questions1. Define microscope.

2. Name types of microscope.

3. What is a simple microscope?

4. Give uses of simple microscope.

5. Which type of lens is used as a simple microscope?

6. Explain magnification of a simple microscope. How it can be increased?

7. The focal length of lens used in a simple microscope should be small. Why?

8. What is a compound microscope?

9. Define objective lens.

10. Define eye piece.

11. How many lenses are used in compound microscope?

12. What is magnification of compound microscope?

13. Give differences between simple microscope and compound microscope.

Importance of micro-organisms.• Who are micro organisms?

• Organisms that we cannot see with our naked eye are called micro – organisms.

Uses of micro organisms1. Compost Production2. Coir industry3. dairy products

I. CurdII. YoghurtIII. Cheese

4. Vinegar production5. Production of immunization vaccines and antibiotics

Compost Production

• Compost is produced in two main ways.1. House hold production on small scale.2. Industrial production on large scale.

• Different methods of compost production1. Pit method 3. Barrel method

2. Land method 4. Basket method

Coir industry

Coconut husks are soaked in water

dairy products

• Curd

Buffalo milk

filtering

boiling

Remove scum

and cool to room te

mp.

Add few

spoons of

curd sa

mple

poured into pot

s and kept for 12

hours for

setting

• Yoghurt

• Bacteria that added to milka. Lactobacillus bulgaricusb. Streptococcus thermophiles

• The Lactobacillus bacteria convert the lactose present in the milk to lactic acid. As the yoghurt gets acidic it becomes unfavorable for other bacteria.

cows milk or

sheep

milk

milk is heated for 15 –

30 minutes

at a temperature of 88 0C – 95 0C

Add

bacteri

a

Keep for 3 -

6 hours

at 40 C – 45 C

Keep in refrigerator to

stop further bacteri

al actions

• Cheesethe fat and

protein

content of the milk

is adjusted as requir

ed

stirred and

pasteurized

Lactobacillus

or Streptococcu

s bacteri

a is added

or inocula

ted and

left for fermentation

special

enzymes are

added to the fermented milk and

allowed to coagulate

semi-solid milk

mixture is

filtered to

remove the

liquid portion, and the partially

dried solid

portion is

pressed

the chee

se mixture is seasoned

by adding

bacteria

Vinegar production• Coconut toddy is used to produce natural vinegar. The sweet sap that

exudes out of the cut end of an unopened flower (inflorescence) of a coconut tree is called ‘sweet toddy’.

• The microbe yeast present in the air get into sweet toddy and fermentation takes place, as a result ethyl alcohol is produced in coconut toddy. Ethyl alcohol is converted to acetic acid by action of bacteria.

Sweet toddy ethyl alcohol

Ethyl alcohol acitic acid (vinegar)

fermentation byyeast

bacteriaacetobactor

Production of immunization vaccines and antibiotics

• Immunization vaccines.

It is a vaccine given to a person to prevent him/her from getting infectious diseases. These vaccines may have at least one of the ‘antigens’ given below.

1. Distroyed or inactivated causative agent e.g. Polio and rabies vaccine2. Live causative agent whose growth is inactivated.e.g. Measles, mumps, chicken pox and rubella vaccines.3. Toxicity of the causative agent is inactivated chemically.e.g. Diphtheria, Tetanus vaccines.4. Parts of causative agent cells or viruses (vaccine produced using genetic engineering)

e.g. Hepatitis B vaccine

• Antibiotics

• What is antibiotics?• An antibiotic is a substance produced by one micro-organism that is capable of

destroying or inhibiting the growth of another micro-organism.• The chemical substances that destroy the bacteria are called antibiotics.

Antibiotics are used to cure diseases infected by bacteria and some fungi. (Antibiotics do not harm human body cells)

• antibiotics are used to control infectious diseases in humans and also in animals useful to them. Even though antibiotics are not harmful to human body cells, side effects such as allergies can occur. Antibiotics are not effective against viruses.

Self Assessment questions1. State 5 main uses of micro organisms?2. What is the main importance of compost fertilizer?3. State main production methods of compost?4. From above method what is the most effective method in urban

areas?5. What areas in sri lanka popular for coir industry?6. When making curd what are the purpose of filtering and boiling?7. Why we add already make curd sample into milk?

Harmful effects of micro-organisms• Two main harmful effects that are caused by micro-organisms,

1. Infectious diseases2. Food spoilage

Infections• Generally, we refer to these causative agents as ‘pathogens.’• These pathogens belong to either bacteria, viruses, fungi or

unicellular organisms.

Bacteria• Causative bacteria for tuberculosis, damages the lungs or bones in the early

stages.• Causative bacteria for syphilis damages reproductive organs in the early stages.• Causative bacteria for pneumonia damages lungs.

• The diseases may spread to other parts of the body due to the improper treatment. Some bacteria secrete digestive enzymes which digest parts of some organs in the body while some species of bacteria secrete toxic substances causing diseases.

Viruses• Target cells of the common cold virus are the epithelial cells of the

lining of the nasal passage.• Target cells of the rabies virus are the nerve cells of the brain.• Target cells of HIV is a type of white blood cells. (T4 - limphocyte)

Fungi• Aluham - Pityriasis versicolor• Infections in the mouth or organs of reproductive system (candidiasis)

Candida fungi

• Saprophytic, disease causing fungi secretes enzymes to the outside or on to the host which destroy the tissues and the organs of the host causing irritation and inflammation.

Unicellular organisms• Disease causing protozoans (unicellular organisms) usually live in the

blood system, lymphatic system or digestive system

Disease Place of entry of the causative agents

Eye disease Eye

Diseases in the digestive tract Mouth

Diseases in the reproductive system Reproductive openings

Malaria, filaria, Dengue Insect bites on the skin

Rabies Carrier dog bite or saliva of a rabied dogthrough a wound

Spread of causative agents• By means of air• By means of water• By means of food• By means of contact• By means of vectors

By means of air

common cold

tuberculosis

Leprosy

meningitis

By means of water

amoebic dysentery

cholera

typhoid

means of food

typhoid

amoebic dysentery.

means of contact

dermatitis

syphilis bacteria

means of vectors

• Malaria parasite by Anopheles mosquito

• Filaria parasite by Culex mosquito

• Dengue causative agent by Aedes mosquito

• Rabies causative agent by mammals like dogs, cats, monkeys etc

Food spoilage• Food spoilage is the change of physical and chemical nature of the

food and as a result food become unsuitable for consumption

There are three ways of food spoilage

Lipids and oil -

Rancidification

Carbohydrate -

Fermentation

Protein - Putrefacti

on

• Commonly, food spoilage occurs due to bacteria and fungi. If fully ripen fruits or cooked food is kept uncovered, spoilage occurs more quickly. The fruits and food get spoiled due to the action of the digestive enzymes secreted by the micro-organisms. Spoiled food is not suitable for consumption.

• If fresh meat or fish is kept uncovered flies will bring different types of bacteria and deposit on them and due to the activity of these bacteria food get spoiled.

• Bacteria and fungi grow very fast under warm conditions. Hence, food is subjected to spoilage at room temperature (25oc - 32oc). You can minimize this spoilage by keeping food in a refrigerator (4oc) or a freezer(-20oc).

• Examples : milk, meat, fish• Activity of the microorganisms can be controlled by adding chemicals that preserve food, e.g.

fruit juice, cordials. Microbial activity can be prevented by adding salt or keeping food dipped in thick honey. (fruits stored in syrup, lime pickle, “jadi” and dried fish are some examples).

Using laboratory equipment appropriately1. Volumetric equipment2. Instruments to measure mass / weight3. Instruments to measure quantities related to electricity.4. Other laboratory equipment

Volumetric equipment

1. Measuring Cylinder2. Beaker3. Pipettes and Burettes.4. Flasks

Measuring Cylinder

• Available in milliliters or cubic centimeters.

Beaker

• Beakers are used for heating various liquids for making and mixing solutions to get approximate volume measurements.

Pipettes and Burettes.

• There are two kind of pipets.1. Bulb pipettes

2. Graduated pipettes

3. Burette

Flasks

Instruments to measure mass / weight1. Triple beam balance2. Chemical balance.3. Spring balance.

Triple beam balance

Chemical balance.

Spring balance.

Instruments to measure quantities related to electricity.

1. Ammeter2. Voltmeter3. Multi meter

Ammeter

Voltmeter

Multi meter

Other laboratory equipment

• Boling tubes, test tubes and ignition tubes• Funnel• Thistle funnel• Watch glass, petri dish, slide and cover slip, trough• Density bottle• Bunsen burner• Spirit Lamp• Tripod• Mortar and pestle• Cork-borer• Wash bottle• Filter papers• Crucible tong and forcep.

GOOD BYE!!!!