CBSE Class 3 Science Our Body Worksheet

How do you preserve food? Why do you preserve food?
Food can be preserved by different methods. Preservation of food prevent the gradual spoiling of food by disease causing organisms.

The common methods of food preservation are:
1. Pasteurization: - boiling in moderate heat. e.g. milk
2. Sterilization: - Boiling or heating to a maximum heat. e.g. food equipments
3. Drying: -Evaporating the water content. e.g. meat
4. Heating: -Cooking with heat. e.g. vegetables and meat
5. Cooling: - by refrigeration. e.g. fruits, milk, meat, etc.

Hygienic Latrines

Hygienic Latrines: are specially designed pits (holes) for defecation.
They are important to prevent faecal-borne diseases like ascaris, tape worms and Hook warms.
The following is the path ways of faecel-born disease transmission

DISEASES AND PREVENTIVE MEASURES

A disease is anything that disturbs the normal body function of an organism partially or completely. Both plants and animals can be infected with various diseases.

Causes of Diseases

The normal body functions of an organism can be disturbed for various reasons. Microbes germs and parasitic worms are the major causes of diseases. The shortage or insufficiency of nutrients also causes a disease called deficiency diseases.

Diseases Caused by Harmful Microorganisms/ germs/

Harmful micro-organisms /germs/ are tiny living organisms that cause many diseases. The germs are very small. Thus, germs can be seen only with the help of the microscope. If these germs enter our body they multiply and produce toxin that poison the body. Diseases such as cholera, tuberculosis, HIV/AIDS, typhoid, malaria, rabies and etc are caused by harmful microorganisms/germs/. These germs include viruses, protozoa, bacteria and fungi. All microorganisms are not disease causing organisms.

A. Cholera
Cholera is a bacterial disease. It is caused by vibro-cholerae. The bacterium causes diarrhea which results in the loss of water and salts from the body. If the loss of body fluid is too much it results in shortage of water and finally death.

B. Tuberculosis/TB/
Tuberculosis is caused by a bacterium called Mycobacterium tuberculosis. The bacterium infects the lungs. Cough, loss of body weight and blood containing sputum are symptom of tuberculosis.

C. Common Cold
Common Cold iscaused by viruses. It transmits from the infected person to the healthy person. Sneezing, coughing, headache and sputum are some of the symptoms of common cold.

D. AIDS/Acquired Immuno Deficiency Syndrome/
AIDS is a serious disease which damages the human natural immune system. AIDS is caused by human immuno virus/ HIV/. AIDS virus spreads by, infected blood transfusion and from mother to baby. Loss of body weight (˜10%), fever, loss of appetite, persistent diarrhea, dry cough etc. are some of the symptoms of AIDS. AIDS is not only health problem but it is also economic, political and social problem. Many developing countries including Ethiopia are running shortage of productive man power. Thus the effects of AIDS at individual, family level and nationwide is very great.

A. Effects of AIDS on individual
- Stigma and discrimination from friends, family or colleagues
- Extra expense may affect the income of the individual.

B. Effects of AIDS on family
- Extra expenses may affect the income of the family
- Break down of family due to death of parents

C. Rabies
Rabies is a disease of dogs and other animals. It causes madness and death. Rabies is caused by rabies virus. The disease is transmitted to healthy animals or, humans when bitten by infected animals. Slight fever, sore throat, headache, inability to swallow and foaming at mouth are symptoms of rabies.

D. Amoebiasis
Amoebiasis is caused by protozoa called entamoeba histolytica. Amoebiasis is sometimes known as amoebic dysentery. The disease causes diarrhea with loss of blood and mucous.

E. Malaria
Malaria is caused by microscopic protozoa called Plasmodium.
It is transmitted from one person to another by the bite of female anopheles mosquito. The female anopheles mosquito sucks blood from our body for the development of her reproductive organ. High fever, headache, heavy sweating, shivering and chills are symptoms of malarial disease.

Diseases caused by parasitic Worms
Harmful microorganisms are not the only living things that cause diseases. Parasitic worms like ascaris, hook worm, bilharzias, tapeworm, Schistosoma and so on also cause diseases. These are parasitic worms that cause various diseases. Some of these parasitic worms live in our intestine while others live in our blood vessels. Ascaris, hookworm and tapeworm are examples of. intestinal parasites while schistosoma and bilharzias live in blood vessels.

A. Ascariasis
Ascaris lives in the small intestine of man. It absorbs digested nutrients from the small intestine. A person infected with ascaris becomes weak because the worm takes most of the digested food from his intestine. Ascaris causes ascariasis.

B. Tapeworm
Tapeworm also lives in the small intestine of infected person. It absorbs digested nutrients from the intestine. Tapeworm lives for a long period in the small intestine by attaching itself to the wall. Eating raw meat may result in tapeworm infection. Tapeworm causes taeniasis.

C. Schistosomiasis / Bilharziasis
The bilharzia/ Schistosoma/ is a parasitic worm that lives in the blood vessels of infected person. Bilharzia makes the infected person very weak. Reducing capacity of bladder, failurity of ureter openings to keep urine back, enlargement of spleen liver and etc. are symptoms of bilharziasis.

Deficiency Diseases
Diseases caused due to the shortage of nutrients are called Deficiency diseases. Deficiency diseases cannot transmit from one person to another. To prevent deficiency diseases, we must eat a balanced diet that contains all nutrients such as carbohydrates, proteins, lipids, vitamins and minerals.

4.2 Ways of Diseases Transmission

Diseases spread from an infected person to healthy persons in a number of ways. Those diseases
spread from an infected person to healthy persons are called communicable /infectious/ diseases. Microbes/germs/ and parasitic worms usually enter to our body across skin and through natural openings such as mouth, nose, eye, and anus. Microbes and parasitic worms enter to the body across our skin when there is open wound, scratch, insect bite and cuts on it. Sharing the same needle with contaminated needle, also transmit diseases from one person to another.

1. Skin
Our skin is an open door for a number of diseases causing organisms to enter our body.

1.1 Ways of disease transmission across the skin

i. Insect bites
Insects such as mosquito, flea, louse etc. transmit disease causing germs across the skin through biting. Also infected dogs and cats transmit disease causing microbes by biting.

ii. Contaminated needles
Sharing the same needle for injection can transmit diseases from one person to another. HIV and Hepatic viruses can spread through contaminated needle shared among many persons. Also, sharing razor blade and tooth brush may spread diseases from infected person to healthy persons.

iii. Wound
Disease causing germs can get entered to our body when there is open wound in the skin. A healthy person gets infected when his skin comes in contact with wound of infected person. But, germs cannot penetrate the surface of our skin easily without wound.

iv. Boring Skin/ piercing skin/
Hook worm and the larvae of bilharzias worm enters to our body by piercing /boring/ skin. If bilharzias entered into the body they cause disorder in the body. They usually pierce our skin where it is soft like between toes.

2. Natural openings

Diseases transmit through natural openings
Natural openings such as nose, mouth, anus, eyes and ear, can serve as entrance of disease causing germs to our body. These openings serve as a door for entrance of germs to our body.

2.1 Ways of disease’s transmission through natural openings

i. Mouth
Disease causing germs can enter into our body through mouth with contaminated food and water. Diseases such as cholera, and typhoid, so on enter to our body through mouth with contaminated food and water. These diseases are called water and food born diseases respectively. Therefore, mouth is the natural opening that serves for entrance of germs with food and water.

ii. Nose/ Air-borne diseases/
When an infected person coughs, sneezes or spits, germs from his respiratory organ are thrown out into air. A healthy person breathes in these germs with air through his nose and gets infected with them. Diseases like common cold, influenza, and tuberculosis whooping cough, diphtheria, chicken pox, and measles enter into our body through nose. These diseases are called air- borne diseases.

iii. Eye
Our eye is another natural opening through which germs enter into the body. Flies or dirty hands can bring harmful microbes/germs/ from air or dust to our eyes. Then the germs enter to the eyes and cause diseases such as trachoma and conjunctivitis. We have to wash our face every morning with soap and water to avoid eye-diseases.

4.3 DISEASE PREVENTION MEASURES

We have learnt that diseases transmit from one person to another person in a number of ways. Contaminated food and water, sharing the same needles, razor blade and tooth brush transmit diseases from person to person. We can prevent the transmission of diseases in a number of ways. In this section we shall learn preventive measure of diseases.

1. Keeping personal Hygiene

Personal hygiene can be kept by:
• bathing/washing our body every week/
• brushing our teeth before and after every meal
• making our nail short and clean
• washing our clothes when they are dirty
• washing our face and feet every day etc. are personal hygiene that prevent the transmission of diseases from person to person.

2. Community Hygiene

• Removing wastes from households and surrounding area should be disposed in a safe place.
• Using of latrine is examples of community hygiene.

3. Vaccination

Vaccines are substances that make our body to resist diseases. Children should be vaccinated against deadly diseases like measles, whooping cough, tetanus, poliomyelitis, meningitis and etc.

4. Eating Balanced diet
A balanced diet contains all classes of nutrients. Thus eating balanced diet makes our bodie resist against diseases.

5. Food and water Hygiene
Food and water contaminated with germs can spread diseases. Eating uncovered or unclean food and drinking dirty water can cause diseases like amoebic dysentery, cholera, typhoid, tuberculosis and so on. Thus, the water we drink as well as the food we eat must be clean and free from germs.

6. Wearing shoes
Wearing shoes prevents those parasites that enter to our body by boring feet. Example Hook worm, larvae of bilharzias.

7. Avoiding eating raw meat
Eating raw meat causes taeniasis. Thus we have to avoid eating raw meat.

8. Avoiding sharing needles or sharp objects
Sharing needles or sharp objects like razor blades can transmit diseases. AIDS and liver virus can be transmitted by sharing these object