The NIOS Class 12 Biology Some Common Human Diseases chapter explains causes, symptoms, prevention, and treatment of diseases like malaria, tuberculosis, and AIDS. Students learn about pathogens and public health measures. With solved terminal exercises, exam preparation becomes easier.
This chapter builds awareness about health issues and their impact on society. It is both educational and practical, helping learners prepare for exams and real-life applications in NIOS Class 12 Biology studies.
NIOS Class 12 Biology Some Common Human Diseases
1. What is a disease? How does it differ from disorder?
Any malfunctioning process that interferes with the normal functioning of the body is called a disease. In other words, disease may be defined as a disorder in the physical, physiological, psychological, or social state of a person caused due to nutritional deficiency, physiological disorder, genetic disorder, pathogen, or any other reason.
2. Name the two categories of acquired diseases.
- Infectious diseases
- Degenerative diseases
3. Explain the terms (i) parasitism, (ii) reservoir.
- Parasitism: In this type of interaction, one species is harmed and the other benefits. Parasitism involves small-sized organisms or parasites living in or on another living species called the host, from which the parasite gets its nourishment and often shelter.
- Reservoir: An organism that harbours pathogens in large numbers that do not cause any suffering to it.
4. Give two symptoms of coronary diseases and of typhoid.
- (i) Persistent high blood pressure (BP)
- (ii) It may damage the arteries of the kidneys.
- (iii) In extreme cases, the arteries may burst or blindness may be caused.
- (iv) It may also cause paralysis.
Typhoid
- (i) Continuous fever, headache, slow pulse rate.
- (ii) Reddish rashes appear on the belly.
- (iii) In extreme cases, ulcers may rupture, resulting in the death of the patient.
5. What precautions should be taken to prevent malaria?
Prevention and cure
- (i) Fitting of double doors and windows (with “Jali,” i.e., wire mesh) in the house to prevent entry of mosquitoes.
- (ii) Use of mosquito nets and mosquito repellents.
- (iii) No water should be allowed to collect in ditches or other open spaces to prevent mosquito breeding.
- (iv) Sprinkling of kerosene oil in ditches or other open spaces where water gets collected.
- (v) Antimalarial drugs to be taken.
6. Name the pathogen that causes diphtheria and the one that causes cholera.
- Diphtheria: Rod-shaped bacterium (Corynebacterium diphtheriae)
- Cholera: Comma-shaped bacterium (Vibrio cholerae)
7. Mention the four types of acquired diseases.
Acquired diseases may generally be classified into:
- (i) Infectious diseases: The diseases that can be transmitted from a diseased person to a healthy person. e.g. measles.
- (ii) Degenerative diseases: The diseases caused by the malfunction of some vital organs of the body, e.g., heart failure.
- (iii) Deficiency diseases: These are caused due to nutritional deficiency, such as that of minerals or vitamins in the diet, e.g,.Anemia (Fe), Beri-beri (vitamin
- (iv) Cancer: This is an abnormal, uncontrolled, and unwanted growth of cells. E.g.,. Breast cancer.
8. Differentiate between:
(i) Communicable and non-communicable diseases
(ii) Pathogen and vector
(iii) Syphilis and gonorrhoea
(iv) HIV and AIDS
(v) Benign and malignant tumours
(i) Communicable and non-communicable diseases
| Communicable diseases | Non-communicable diseases |
| 2. Spread from one person to another through contact, water, air, and food, etc. | Caused due to some specific factor, such as malfunctioning of some vital organ, and deficiency of nutrients. |
| 3. The concern of the diseases involves society, as these are related to community health. | Do not spread from one person to another by contact. |
| The concern of the disease is restricted to the individual only. | The concern of the disease is restrictedto the individual only. |
(ii) Pathogen and vector
- Pathogen: A living organism that causes a disease.
- Vector: It is an organism that harbours a pathogen and may pass it on to another person to cause a disease (Mosquitoes harbour the malarial parasite and transmit it to humans).
(iii) Syphilis and gonorrhoea
Syphilis is a sexually transmitted disease caused by Treponema pallidum, a long, corkscrew bacterium. It is spread by having sexual contact with an infected person.
Gonorrhoea is another sexually transmitted disease affecting the genital organs, anus, throat, etc. It is caused by a gonococcus Neisseria gonorrhoeae bacterium.
(iv) HIV and AIDS
HIV is Human Immunodeficiency Virus, the causative organism that leads to AIDS.
AIDS is Acquired Immune Deficiency Syndrome, a condition affected due to HIV infection, where the immune system of the human body is compromised.
(v) Benign and malignant tumors
- Benign tumours remain confined to the place of origin and do not spread to other body parts, and are relatively harmless.
- Malignant tumours spread to other parts of the body, and growth is rapid. This is serious and may cause the death of the patient.
9. How does the polio virus enter the human body? How does it paralyse limbs?
Polio virus enters the body through food or water. It damages the brain and nerves and causes infantile paralysis.
10. A nursing mother is given an immunization for BCG and DPT for the baby. What are the diseases against which she would be protected?
- BCG prevents the development of tuberculosis vaccine.
- DPT is a vaccination against diphtheria, tetanus, and pertussis.
11. Give the cause, symptoms, and treatment of hemorrhagic dengue fever.
Dengue hemorrhagic fever is an acute infectious viral disease. It is an advanced stage of dengue fever.
Symptoms of Dengue hemorrhagic fever
- (i) Severe and continuous pain in the abdomen.
- (ii) Rashes on the skin.
- (iii) Bleeding from the nose, mouth, or in the internal organs.
- (iv) Frequent vomiting with or without blood.
- (v) Black stools due to internal bleeding.
- (vi) Excessive thirst (dry mouth).
- (vii) Pale, cold skin, weakness.
Dengue hemorrhagic fever is treated by replacing lost fluids. Some patients need blood transfusions to control bleeding.
12. Give the full form of STD.
STD: Sexually Transmitted Diseases
13. Mention any two symptoms of syphilis.
The common symptoms of syphilis include.
- (i) Fever, and sores on the skin, in the throat and urinogenital areas, especially vagina or penis, anus, rectum, and mouth. Sores are firm, round, and often painless.
- (ii) Rashes on hands, feet, and palms.
- (iii) White patches in the mouth.
- (iv) Acne-like warts in the groin area.
- (v) Hair fall in patches from infected areas.
- (vi) The last three symptoms can be very serious. They often become internal and affect organs like the brain, nerves, liver, eyes, blood vessels, bones, and joints, which show up after about 10 years of getting the infection. It can lead to paralysis, blindness, dementia, and sterility.
14. State the means by which we may prevent and cure gonorrhoea.
Prevention and cure of gonorrhoea
- (i) Having sexual contact with only one person.
- (ii) Avoiding prostitution and homosexuality.
- (iii) Taking antibiotics, such as penicillin injection or appropriate medicines at the appropriate time as per the Doctor’s advice.
15. What does the term AIDS stand for?
AIDS: Acquired Immune Deficiency Syndrome
16. Write four possible symptoms of AIDS.
Symptoms of AIDS:
- (i) A type of lung disease develops (tuberculosis).
- (ii) A skin cancer may be observed.
- (iii) Nerves are affected.
- (iv) The brain is badly damaged with the loss of memory, the ability to speak, and to think.
17. Mention three general points that may control sexually transmitted diseases.
- The blood to be transfused to the needy person should be free from the HIV germ.
- Prostitution and homosexuality should be avoided.
- Condoms should always be used during intercourse.
