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Health: The Ultimate

Treasure Class 8
Notes Science
Chapter 3
August 12, 2025 by Bhagya

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Health: The Ultimate Treasure Class 8 Notes
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Class 8 Science Chapter

3 Health: The Ultimate
Treasure Notes
Class 8 Health: The Ultimate
Treasure Notes
Class 8 Science Chapter 3 Notes – Health: The
Ultimate Treasure Notes Class 8

→ Health: Health is complete physical, mental,

and social well-being, not just the absence of
disease (WHO).

→ Health Components: Involves physical fitness,

positive mindset, and strong social relationships.

→ Ayurveda’s View: Health is a balance of body,

mind, and surroundings via daily/seasonal
routines, diet, and yoga.

→ Healthy Habits: Maintain hygiene, eat a

balanced diet, exercise regularly, get enough
sleep, and limit screen time.

→ Unhealthy Habits: Avoid excessive screen time,

junk food, late sleep, and skipping meals.

→ Environmental Health: Clean surroundings and

air (monitored by AQI) reduce respiratory issues
like asthma.

→ Symptoms vs. Signs: Symptoms are felt (e.g.,

pain); signs are measurable (e.g., fever, rash).

→ Communicable Diseases: Caused by

pathogens (bacteria, viruses, etc.) and spread via
air, contact, food, or vectors, e.g., Typhoid, dengue,
flu, chickenpox, COVID-19.

→ Non-Communicable Diseases (NCDs): Linked to

lifestyle, diet, or environment; e.g., diabetes,
cancer, asthma.

→ Deficiency Diseases: NCDs caused by nutrient

deficiencies, e.g., anaemia, scurvy, goitre.

→ NCD Prevalence: Diabetes and heart disease

are rising in India due to processed foods and
sedentary lifestyles.

→ Disease Prevention: Hygiene, clean water, and

sanitation (e.g., Odisha’s campaign) reduce
communicable diseases.

→ Vaccines: Train the immune system to prevent

diseases like tetanus, polio, hepatitis, and
measles, not cure them.

→ Immunity: The body’s natural defense; it varies

among individuals; vaccines provide acquired
immunity.

→ Antibiotics: Treat bacterial infections, not viral

ones; overuse leads to resistant bacteria.

→ Antibiotic Resistance: Makes infections harder

to treat; prevented by proper antibiotic use.

→ Traditional Medicine: Ayurveda, Siddha, and

Unani promote well-being but may not treat all
diseases.

→ NCD Management: Uses medication, lifestyle

changes, and early diagnosis to control
symptoms.

→ Key Scientists: Kamal Ranadive (cancer

research), Maharaj Kishan Bhan (Rotavirus
vaccine), Edward Jenner (smallpox vaccine),
Alexander Fleming (penicillin).

→ Health: A state of complete physical, mental,

and social well-being, not merely the absence of
disease (WHO).

→ Well-being: The condition of being healthy,

happy, and comfortable in physical, mental, and
social aspects.

→ Pathogen: A disease-causing organism, such

as worms, bacteria, fungi, viruses or protozoa.

→ Communicable Disease: A disease caused by

pathogens that can spread from one person to
another (e.g., flu, dengue).

→ Non-Communicable Disease (NCD): A disease

not caused by pathogens and not transmissible,
often linked to lifestyle or environment (e.g.,
diabetes, cancer).

→ Immunity: The body’s natural ability to resist

and fight diseases through the immune system.

→ Vaccine: A substance that trains the immune

system to recognize and fight specific pathogens,
preventing diseases.

→ Acquired Immunity: Protection developed after

exposure to a pathogen or vaccine, enhancing
immune response.

→ Antibiotic: A medicine that kills or inhibits

bacteria, used to treat bacterial infections but not
viral ones.

→ Antibiotic Resistance: When bacteria survive

and multiply despite antibiotic treatment,
reducing drug effectiveness.

→ Symptom: A subjective indication of illness felt

by the patient, such as pain or tiredness.

→ Sign: An objective, measurable indication of

illness, such as fever or a rash, observable by
others.

→ Hygiene: Practices like handwashing and

cleanliness that prevent the spread of diseases.

→ Lifestyle: Daily habits and behaviours (e.g., diet,

exercise) that impact health and disease risk.

→ Environment: Surroundings, including air and

water quality, that affect health (e.g., pollution
causes respiratory issues).

→ Vector: An organism, like a mosquito, that

transmits pathogens causing diseases such as
malaria or dengue.

→ Prakriti: In Ayurveda, an individual’s unique

body constitution that influences diet and health
practices.

→ Dinacharya: Ayurvedic daily routine to maintain

health through balanced habits like sleep and
exercise.

→ Chronic Disease: A long-term condition (lasting

over 3 months) like diabetes or asthma, requiring
ongoing management.

→ Sanitation: Measures like access to clean water

and toilets that reduce disease spread, as seen in
community campaigns.

→ Health means complete physical, mental, and

social well-being, not just the absence of disease.

→ Being happy helps us stay active and healthy,

and good health also improves our mood. Health
and happiness are closely related.

→ A disease affects the normal working of the

body or mind.

→ Symptoms are what we feel (like pain or

tiredness); signs are what can be seen or
measured (like fever or rash).

→ Non-communicable diseases like diabetes and

heart disease are caused by lifestyle and
environmental factors, not germs. They can often
be prevented with healthy habits, lifestyle
changes, and regular exercise.

→ Pathogens like bacteria, viruses, or worms

cause infectious diseases.

→ Our immune system helps protect us from

harmful pathogens.

→ Vaccines train the immune system using dead,

weakened, or harmless parts of a germ to prevent
disease.

→ Diagnosis and treatment are important for

managing and curing diseases.

Health: Is It More Than Not

Falling Sick? Class 8 Notes
What do the news clippings on the notice board
tell you about people’s health in our country? Is
being healthy just about not having diseases?
Health also encompasses feeling physically well,
maintaining a positive outlook, and fostering
strong relationships. A healthy person takes care
of their body, maintains a positive mindset, and
enjoys social life. Let us now explore what it truly
means to be healthy.

Activity 1: Let us read

A Grade 8 student moved to a new school in
another city. With no friends in his new
environment and busy parents, he felt lonely. To
cope, he spent more time on his phone and social
media, but this made him feel worse. He stopped
trying to make friends, had headaches, lost
weight, and could not sleep well. A doctor advised
less screen time and meeting a counsellor. The
school counsellor arranged help to support him in
making friends and improving his health.

Think and Reflect: What was the cause of the

boy’s health problems? How did his habits and
surroundings affect his well-being? As per the
World Health Organization (WHO), health is
defined as a ‘state of complete physical, mental,
and social well-being, and not merely the absence
of disease’.

A healthy person can perform various tasks more

efficiently and cope well in different and difficult
situations. A healthy person can adjust well with
peer groups and other members of society. Let us
understand more about health.

Ayurveda teaches us that true health is a balance

of body, mind, and surroundings. Following
dinacharya (daily routine) and ritucharya
(seasonal routine) helps maintain this balance.
Eating fresh, wholesome food suited to one’s
prakriti (body constitution) is essential. Regular
exercise, cleanliness, restful sleep, and a calm
mind support overall well-being. This can also be
achieved through practices like yoga, meditation,
and mindfulness.

How Can We Stay Healthy?

Class 8 Notes
Staying healthy means eating nutritious food,
maintaining hygiene, staying in a clean place,
exercising regularly, getting proper sleep,
spending time with family and friends, and having
a positive attitude. What should we do and what
should we not do to keep ourselves healthy?

Activity 2: Let us list

List some good habits that your parents, teachers,
or elders often encourage you to follow. How
many of these are already a part of your daily
routine? Which ones would you like to start
following? Add to the list below:

Keep yourself clean and maintain personal

hygiene.
Eat a healthy and balanced diet.
Exercise regularly.
Make time to relax or meditate every day.

Now, think about habits that are not good for your
health. Add more to the list below:

Spending too much time on mobile phones

or other digital screens.
Eating fast food and other junk food every
day.
Sleeping very late or not getting enough
sleep.
Skipping meals, especially breakfast.

Taking care of our body and mind is important.

Healthy habits support a healthy body as well as
a healthy mind. Discuss your findings with your
friends and teacher. From the activity you
participated in and the discussions, you may have
realised that our health depends on many factors.
These factors include our lifestyle (how we live)
and our environment (our surroundings).

Maintain a Healthy Lifestyle

Class 8 Notes
Eat a balanced diet with plenty of fruits,
vegetables, and whole grains. Avoid processed,
fatty, or sugary food and drinks. Stay physically
active by playing outdoors, walking, running,
cycling, or exercising. Limit screen time and spend
more time in nature. Get enough sleep to help
your body and mind rest and recover. Practice
yoga or simple breathing exercises like
pranayama regularly. Say ‘NO’ to harmful
substances like tobacco, alcohol, and addictive
drugs.

Keep the Environment Clean

Class 8 Notes
Activity 3: Let us compare
Look at Figures a and b. Which playground would
you like to play in, and why?
Most of us would like to play in the playground
shown in Figure A as it is clean, well-maintained,
and looks beautiful. The playground in Figure b is
polluted, dirty, unhygienic, and full of flies and
mosquitoes. People living in such areas may fall
sick more often.

In addition to inculcating good habits and

adopting a healthy lifestyle, we must keep
ourselves and our surroundings clean. Have you
ever found it hard to breathe in a place with a lot
of smoke or dust? That is because clean air and
water are important for our health. In cities, air
pollution from vehicles and factories can cause
problems like coughing or asthma. The Air Quality
Index (AQI) helps us know how clean the air is. A
cleaner environment helps us stay healthy and
feel better. But health is not only about the body.
Our feelings and relationships matter too. Even if
we eat well and live in a clean place, we may not
feel good if we are lonely or upset. Spending time
with friends and family, talking, laughing, and
having fun helps keep our minds healthy too.

How Do We Know That We Are

Unwell? Class 8 Notes
Our body usually works in a certain way to keep
us healthy. When we feel unwell, it means
something inside us may not be working as it
should. We may have symptoms, such as pain,
tiredness, or dizziness, and signs like fever, rash,
high blood pressure, or swelling that indicate we
are unwell. A symptom is what we feel (like pain),
while a sign is something that can be seen or
measured (like high body temperature when we
have a fever). These help doctors understand
what might be making us unwell.

Diseases: What Are the Causes

and Types? Class 8 Notes
A disease is a condition that affects the normal
working of the body or mind. It can happen when
one or more organs or organ systems stop
functioning properly. Some diseases are caused
by germs like bacteria, viruses, fungi, worms, or
even by protozoa (single-celled organisms).
These disease-causing organisms are called
pathogens. Other diseases may result from poor
nutrition or an unhealthy lifestyle. Some diseases
last for a short time, while others can continue for
a long time and need regular treatment or care.
Diseases can be grouped into two major types
based on their causes and how they spread:

Non-communicable diseases: Some

diseases, like cancer, diabetes, or asthma,
are not caused by pathogens and do not
spread from one person to another. They are
usually linked to lifestyle, diet, and/or
environment.
Communicable diseases: Diseases caused
by pathogens are called communicable
diseases. They can spread from one person
to another. Some examples of
communicable diseases are typhoid,
dengue, flu, chickenpox, and COVID-19.

In recent years, non-communicable diseases

(NCDs) like diabetes, heart disease, and cancer
have become more common in India. This is
happening because of changes in how people live
such as eating more processed food, getting less
exercise, and living longer lives. Today, most
deaths in India are caused by NCDs.
Understanding the difference between these two
types helps us know how diseases spread and
how to prevent them.

How are Communicable

Diseases Caused and Spread?
Class 8 Notes
All communicable diseases are caused by
pathogens. These pathogens can enter our body
through the air we breathe or by consuming
contaminated food or water and more. But how
do these pathogens spread from one person to
another? One common way is through air, when
an infected person coughs or sneezes, or through
direct contact like shaking hands, or indirectly by
sharing personal items of an infected person.
Some of the communicable diseases are spread
through contaminated drinking water or food.
Some pathogens are also spread by insects like
mosquitoes and houseflies. These insects are
called vectors. By understanding how diseases
spread, we can take simple steps to protect
ourselves and others. Let us find out how these
communicable diseases spread and how we can
prevent them.

Activity 4: Let us find out

Grade 8 students listed some common
communicable diseases in Table 1 during a
community campaign and a library survey. Check
the information listed by referring to books,
trusted websites, or asking your science teacher.
Add any missing details. Study the table and think
about what simple steps can help prevent each
disease.

By studying Table 1, we can understand how

infectious diseases spread and how to prevent
them. Here are some simple but important
precautions:

Keeping ourselves and our surroundings

clean.
Practicing basic hygiene every day.
Washing hands with soap and water to
remove pathogens.
Covering our mouth and nose while
coughing or sneezing.
Wearing a mask in crowded places provides
protection.
Avoid sharing personal items like towels
and handkerchiefs.
Keeping our home, food, and water clean.
Staying at home and resting when we are
unwell helps the body recover and
minimizes spreading the disease to others.

Some infectious diseases are caused by worms

that live inside our bodies, especially in the
digestive system. They feed on nutrients and live
as parasitic organisms that live in or on another
living being. These worms usually spread through
contaminated food, water, soil, or contact with
infected people or animals.

How are Non-communicable

Diseases Caused? Class 8
Notes
You learnt that non-communicable diseases like
cancer, diabetes, and asthma are linked to
lifestyle, diet, and/or environment. They are the
most common cause of death in India. In Grade 6,
you also learnt about diseases like scurvy,
anaemia, and goitre, which are caused by a lack
of specific nutrients in the diet. These are called
deficiency diseases and are also non-
communicable.

Diseases such as cancer, diabetes, and asthma

may often persist for a long time (more than 3
months) and are referred to as chronic diseases.
Diabetes is a common disease that is becoming
more prevalent in adults as well as children. India
now has one of the highest numbers of people
with diabetes in the world. It often develops due to
a combination of hormonal imbalances,
unhealthy eating habits, lack of physical activity,
being overweight or obese, and other reasons. Let
us learn more about the causes of non-
communicable diseases and their prevention.

Activity 5: Let us survey

Find out the three most common lifestyle-related
diseases in your neighbourhood. Talk to a doctor,
nurse, health worker, or even a family member
who knows about health and what kind of
lifestyle changes can help prevent or manage
these diseases. You can also consult trusted
health websites, books, teachers, and doctors. Fill
in Table 2 and learn more about lifestyle-related
diseases.

Dr. Kamal Ranadive (1917–2001) was a

pioneering biomedical researcher. She studied
how hormones and certain viruses are linked to
cancer, helping improve its treatment and
prevention. Her work also showed how tobacco,
diet, and pollution can raise the risk of cancer,
highlighting the importance of a healthy lifestyle.

How to Prevent and Control

Diseases? Class 8 Notes
You might have heard the phrase ‘Prevention is
better than a cure.’ It is important to protect
ourselves from both communicable and non-
communicable diseases.

Activity 6: Let us read

Odisha – community-led sanitation campaign
In Bhadrak district, Odisha, a community
sanitation campaign helped more people build
and use toilets. This reduced open defecation
significantly and improved child health, with fewer
cases of diarrhoea and infections. What do you
infer from this case study? Simple steps like good
sanitation can greatly reduce the spread of
communicable diseases. Find out about such
community campaigns held in your location.
Share in your class and discuss with your peers
about the impact of such initiatives.

The ability of the body to fight diseases

You would have noticed that some people get sick
more frequently than others, although living in a
similar environment. Do you know why? The
natural ability of our body to fight diseases is
known as immunity. Our body has a special
system called the immune system that helps fight
against diseases. You might have taken some
drops or injections in your childhood to protect
yourself from certain diseases, such as polio,
measles, tetanus, and hepatitis. These are
vaccines that help prevent serious infections
caused by viruses and bacteria.

A vaccine helps our body fight certain diseases by

training the immune system to recognise and
attack harmful germs. providing what is known as
acquired immunity protection, developed after
exposure to a pathogen or a vaccine. Vaccines
can be made in different ways from weakened or
dead pathogens (like viruses or bacteria), or from
inactive or harmless parts of the pathogen. Some
newer vaccines instruct our body cells to make a
harmless part of the germ, which our immune
system then learns to fight. For example, a
tetanus shot, often given after an injury, protects
against infection by the tetanus-causing bacteria.
It contains an inactivated bacterial toxin that
helps the immune system develop protection
without causing the disease. Do you know when
the first vaccine was discovered?

Edward Jenner and the Smallpox Vaccine

Smallpox was a deadly disease that caused
blisters and killed millions. A milder disease
called cowpox, seen in cows, could also infect
humans. In the late 1700s, English doctor Edward
Jenner discovered that people who had cowpox
did not get smallpox. This led to the invention of
the first vaccine and helped protect people from
smallpox.

Long before modern vaccines, India had a

traditional method called variolation to protect
against smallpox. It involved using material from
a smallpox sore to scratch the skin and create a
mild infection and build immunity. People who
performed this practice were known as
teekedaars.

Think like a Scientist

Observations
Jenner observed that milkmaids who had cowpox
did not catch smallpox, likely because the two
viruses are related.

Hypothesis
Content in the pus of cowpox blisters protected
people from smallpox.

Experimentation
He tested this by injecting cowpox sap into a boy,
who later showed no illness when exposed to
smallpox.

Results
He found that people who were infected with
cowpox sap were now resistant to smallpox.

Application
Mass vaccination eventually helped eradicate
smallpox worldwide.

Vaccines are one of the most effective ways to

protect people of all ages, from infants to the
elderly, against many serious diseases. They help
prevent illnesses, reduce the spread of infections,
and save millions of lives every year. It is
important to remember that vaccines are
preventive, not curative. They can help minimise
serious diseases before they happen, but do not
treat them once someone is already sick. Some
people may fear or doubt vaccines, but scientists
and doctors carefully test them for safety. Getting
vaccinated not only protects you but also the
people around you.

India’s Role in Vaccine Production

India is one of the world’s largest vaccine
producers. It manufactures vaccines on a
massive scale and supplies them to many
countries. Indian vaccine companies played a key
role during the COVID-19 pandemic and continue
to support global health efforts.

Dr. Maharaj Kishan Bhan was a well-known

Indian doctor and scientist. As Secretary of the
Department of Biotechnology, he helped promote
science and innovation in India. He played a key
role in developing the Rotavirus vaccine, which
protects children from diarrhoea. He believed in
using research to create affordable healthcare
and made a big difference in India’s health and
biotechnology sectors.

Treatment of Diseases Class 8

Notes
If our immune system fails to protect us against
an infectious disease, we fall ill and need to visit a
doctor. The doctor may give us medicines called
antibiotics, which kill the bacteria that might have
caused the disease. Antibiotics work only against
bacterial infections because they target parts of
bacterial cells that are different from human or
other animal cells. They do not work against
viruses or diseases caused by protozoa.

Discovery of the first antibiotic, Penicillin

Penicillin was discovered in 1928 by Alexander
Fleming, a bacteriologist from London. While
studying harmful bacteria, he noticed that a
mould on a discarded petri dish stopped the
bacteria from growing. He realized the mould
released a substance that killed the bacteria. This
chance discovery led to the discovery of penicillin,
the first antibiotic used to treat bacterial
infections.

Though antibiotics are effective in protecting us

against bacterial infections and have saved
millions of lives since their discovery, their
indiscriminate use has led to a decline in their
effectiveness.

Nowadays, there are news headlines about

antibiotic resistance, a phenomenon where
bacteria that were earlier killed by a given
antibiotic are found to survive and multiply
despite treatment with that antibiotic. This makes
common infections harder to treat and increases
the risk of complications, prolonged illness, and
even death.

Activity 7: Let us infer

Study the infographic given in Figure. How do you
think the antibiotic resistance has been developed
in bacterial pathogens? What precautions may be
taken to reduce antibiotic resistance? To tackle
the problem of antibiotic resistance, we must use
antibiotics wisely, only when prescribed by a
doctor, in the correct dose, and for the right
duration. Avoiding unnecessary use helps prevent
the rise of resistant bacteria and keeps antibiotics
effective for future generations.

Traditional medicine systems like Ayurveda,

Siddha, and Unani have been used in India for
many years to manage common health problems.
They use natural substances like herbs, oils, and
minerals for managing illnesses and promoting
recovery, and focus on a healthy lifestyle and
balanced diet. While these systems can help with
some conditions and are useful for everyday well-
being, they may not be effective for all diseases
and at all stages. Therapies for non-
communicable diseases focus on managing
symptoms and improving quality of life through
medication, lifestyle changes, and rehabilitation.
Early diagnosis and continuous care are key to
controlling the disease progression and
preventing complications.

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