Class XII Biology Lecture Notes

1. HUMAN HEALTH & DISEASES (L-01)
CONCEPTS:
1. Health:
 It’s a state of complete physical, mental and social well-being.
 Health increases the longevity of people and reduces mortality rate.
 Good health is maintained by balanced diet, personal hygiene and regular exercise.
2. Disease:
 Any condition which interferes with the normal functioning of the body and causes
distress of the mind is called a disease.
3. Classification of diseases:
Diseases can be broadly classified into two types:
a. Infectious diseases
b. Non- infectious diseases
Infectious diseases Non-infectious diseases
1. Transmits from one person to
another.
Cannot be transmitted from one
person to another.
2. They are caused by pathogens Caused by internal factors like
heredity, deficiencies, habits etc.
3. Due to extrinsic factors. Extrinsic as well as intrinsic factors.
4. Common Infectious Diseases:
Infectious diseases are classified as following based on pathogens:
Infectious Diseases
Bacterial
Diseases
Eg. Typhoid,
Pneumonia,
Diptheria,
Bacterial
dysentery,
plague
Viral Diseases
Eg. Common
cold, Polio
Protozoan
Diseases
Eg. Malaria,
Amoebiasis
Fungal Diseases
Eg. Ringworms
Helminthic
Diseases
Eg. Ascariasis,
Filariasis,
Taeniasis
5. Bacterial Diseases:
i. Typhoid
 Caused by pathogenic bacterium Salmonella typhi.
 Transmitted by contaminated food and water.
 Enters the small intestines and then migrate to other parts of the body.

2. Symptoms:
a. Persistent high fever (39 to 40 C) b. Weakness c. Stomach pain d. Loss of appetite
e. Constipation f. Headache
Intestinal perforations and death may occur in severe cases.
Typhoid fever can be confirmed by Widal Test.
MCQs
1. The term health is defined in many ways. The most accurate definition of health would be
a. State of body and mind in balanced condition
b. Reflection of a smiling face
c. State of complete physical, mental and social well being
d. Symbol of economic prosperity.
2. The organisms which cause diseases in plants and animals are called
a. Pathogens
b. Vectors
c. Insects
d. Worms
3. Chemical test used for the detection of typhoid is
a. ELISA
b. ESR
c. PCR
d. Widal
4. Diseases are broadly classified into infectious and non-infectious diseases. In the list given below,
identify the infectious diseases.
a. Cancer
b. Influenza
c. Allergy
d. Smallpox