Notes Chapter 3 Science Curiosity Class 8 CBSE Board

Notes For All Chapters – Science Curiosity Class 8

Health: The Ultimate Treasure

1. What is Health?

• Health is not only about not being sick.

WHO Definition: Health = complete physical, mental, and social well-being.

Healthy person:

• Can work efficiently.
• Adjusts well with friends, family, society.
• Copes with difficult situations.

Example: A boy felt lonely, used more phone and social media, got headaches and sleep problems → showed how emotions affect health.

Ayurveda: Health is balance of body, mind, and surroundings.

• Daily routine (dinacharya).
• Seasonal routine (ritucharya).
• Fresh food, yoga, meditation, mindfulness.

2. How Can We Stay Healthy?

2.1 Healthy Lifestyle

• Eat balanced diet (fruits, vegetables, whole grains).
• Avoid oily, sugary, junk foods.
• Be physically active (sports, walking, cycling).
• Limit screen time.
• Spend time outdoors and in nature.
• Sleep properly.
• Practice yoga, pranayama, meditation.
• Avoid tobacco, alcohol, drugs.

2.2 Clean Environment

• Clean surroundings prevent diseases.
• Dirty areas breed mosquitoes, flies → infections.
• Air pollution → cough, asthma.
• AQI (Air Quality Index) shows air quality.
• Safe water reduces waterborne diseases.

Mental health matters too:

• Loneliness, stress → sickness.
• Family time, laughter, friendship → keep mind healthy.

3. How Do We Know We Are Unwell?

• When body doesn’t function normally → we feel unwell.
• Symptoms (felt): pain, tiredness, dizziness.
• Signs (seen/measured): fever, rash, swelling, high blood pressure.
• Doctors use both to diagnose disease.

4. Diseases: Causes and Types

4.1 What is Disease?

• Disease = condition disturbing normal functioning of body or mind.

4.2 Types of Diseases

1. Communicable diseases

• Caused by pathogens (bacteria, viruses, protozoa, fungi, worms).
• Spread person to person.
• Examples: Cold, flu, chickenpox, measles, TB, cholera, typhoid, malaria, dengue, COVID-19.

Spread by:

• • Air (coughing, sneezing).
  • Direct contact (touch).
  • Indirect contact (sharing items).
  • Contaminated food/water.
  • Vectors (mosquitoes, flies).

2. Non-Communicable diseases (NCDs)

• Do not spread from person to person.
• Caused by lifestyle, poor diet, environment.
• Examples: Diabetes, cancer, asthma, obesity, high blood pressure.
• Include deficiency diseases: anaemia (iron deficiency), goitre (iodine deficiency), scurvy (vitamin C deficiency).
• Many are chronic (long-lasting).

5. Communicable Diseases – Examples

5.1 Airborne Diseases

• Common cold/flu: virus; symptoms = runny nose, cough, fever; prevention = handwashing, covering mouth.
• Chickenpox: virus; fever, rashes, blisters; prevention = isolation, vaccination.
• Measles: virus; sore throat, red rash; prevention = hygiene, vaccination.
• Tuberculosis (TB): bacteria; cough, fever, weight loss; prevention = cover mouth, vaccination, hygiene.

5.2 Food & Waterborne Diseases

• Hepatitis A: virus; fatigue, jaundice; prevention = boiled water, vaccination.
• Cholera: bacteria; diarrhoea, dehydration; prevention = hygiene, clean food/water.
• Typhoid: bacteria; fever, headache, diarrhoea; prevention = hygiene, boiled water, vaccination.
• Ascariasis (worms): worms in intestine; diarrhoea, weight loss; prevention = hygiene, cooked food, boiled water.

5.3 Vector-Borne Diseases

• Malaria: protozoa spread by mosquitoes; fever, chills, sweating; prevention = nets, repellents, mosquito control.
• Dengue: virus spread by mosquitoes; fever, joint pain; prevention = nets, repellents, avoid stagnant water.

6. Non-Communicable Diseases – Examples

• Obesity: due to overeating, no exercise; prevention = healthy diet + activity.
• Diabetes: frequent urination, tiredness, weight loss; prevention = diet control, exercise.
• High Blood Pressure: silent disease; controlled by lifestyle.
• Cancer, Asthma: caused by environment, smoking, pollution.

7. Prevention and Control of Diseases

7.1 Immunity

• Body’s natural defense against disease.
• Strong immunity → fewer illnesses.

7.2 Vaccination

• Provides acquired immunity.
• Made from weakened/dead germs or harmless parts.
• Examples: Polio, measles, tetanus, hepatitis vaccines.
• Edward Jenner (1700s): first smallpox vaccine.
• India’s traditional method: Variolation (before modern vaccines).
• India today: major vaccine producer; played key role in COVID-19 vaccines.

7.3 Treatment

• Antibiotics: kill bacteria, not viruses.
• Alexander Fleming (1928): discovered penicillin.
• Misuse causes antibiotic resistance → bacteria survive despite treatment.
• Use antibiotics only as prescribed.

7.4 Traditional Medicine Systems

• Ayurveda, Siddha, Unani → natural herbs, oils, diet, lifestyle.
• Focus on balance and prevention.

8. Important Scientists

• Edward Jenner: First vaccine (smallpox).
• Alexander Fleming: First antibiotic (penicillin).
• Dr. Kamal Ranadive: Studied cancer, linked hormones/viruses with lifestyle.
• Dr. Maharaj Kishan Bhan: Developed Rotavirus vaccine (for diarrhoea in children).

9. Snapshots (Key Points)

• Health = complete physical, mental, and social well-being.
• Lifestyle + environment affect health.
• Diseases are of 2 main types:
  • Communicable (infectious).
  • Non-communicable (lifestyle/deficiency).
• Symptoms = what we feel; Signs = what we can see/measure.
• Immunity protects us; vaccines build it stronger.
• Antibiotics cure bacterial infections, not viral ones.
• Misuse of antibiotics → resistance.
• Prevention = better than cure → hygiene, clean environment, vaccination, healthy living.