CBSE Important Questions Class 12 Biology Chapter 8

Important Questions Class 12 Biology Chapter 8

Important Questions for CBSE Class 12 Biology Chapter 8 – Human Health and Disease

Important Questions Class 12 Biology Chapter 8 are prepared by subject experts after a thorough analysis of the past years’ question papers. Students need a question set that provides  guided practice and helps  them in understanding what kinds of questions which are important from an exam point of view as well as  the question pattern. These questions follow the CBSE Syllabus. So, it will help students revise the important concepts from the chapter and practise more questions based on them for a thorough reason.

CBSE Class 12 Biology Chapter-8 Important Questions

Study Important Questions for Class 12 Biology Chapter 8 – Human Health and Disease
Students can view a sample of the important questions for Class 12 Biology Chapter 8. They can click on the link provided to access the entire set of questions. 

Very Short Answer Questions (1 Mark)

Q.1. Name the pathogen that causes malaria.

Ans. Plasmodium Falciparum is the pathogen that causes malaria.

Q.2. What is the importance of yeast in medical science?

Ans. Yeast is considered an important microorganism in medical science because it is used to produce the vaccine of Hepatitis B.

Q.3. What causes the shivering in malaria patients?

Ans. After sporozoite infection, when the red blood corpuscles rupture, they release the toxic substance hemozoin in the blood which causes shivering in malaria patients.

Q.4. Why are AIDS patients more susceptible to diseases compared to patients affected by other diseases?

Ans. The HIV virus, which causes AIDS, attacks the immunity system of the human body and weakens it over time, making AIDS patients more susceptible to infections and diseases than patients suffering from other diseases.

Q,5. Write the names of two curable sexually transmitted diseases.

Ans. Syphilis and gonorrhoea are the names of two curable, sexually transmitted diseases.

Q.6. When is a tumour considered malignant?

Ans. When a tumour starts to grow rapidly, causing damage to the normal cells and tissues around it, then the tumour is considered malignant.

Short Answer Questions (2 Marks)

Q.1. Where are B-lymphocytes and T-lymphocytes formed? How do they help develop immunity?

Ans: The B-lymphocytes and T-lymphocytes are formed in the bone marrow of the human body.

The B-lymphocytes protect the body by producing antibodies while the T-lymphocytes immune the body by helping the B-cells produce antibodies.

Q.2. What are allergens? How do they cause inflammatory responses inside the human body?

Ans: Allergens can be defined as substances causing the hypersensitive reaction of the immune system.

When a person comes in contact with an allergen frequently the allergen combines with Ig E on the mast cell. The cells then burst and release Histamines which leads to the inflammatory response.

Q.3 Describe the role of lymph nodes in the human immune response.

Ans: The lymph nodes are the sites in the human body where the lymphocytes and the antigen interact with each other. When microorganisms attack the lymph nodes, the lymphocytes present here get activated and trap  to destroy them.

Long Answer Questions (3 Marks)

Q.1. What is vaccination? Why is it important to take a vaccine?

Ans: Vaccination is a process of developing immunity in the body against pathogens.

A vaccine is a weak pathogen that is injected into the body to produce antibodies against it. These antibodies neutralise the effect of the injected pathogens. Next time, when the vaccinated person gets infected by the same pathogen, but one that is stronger this time, the B lymphocytes and the T lymphocytes will recognise and attack them to protect the body. This type of immunity is called active immunity. However, if a person is severely affected by a pathogen then directly the antibody of the pathogen is injected into the body through a vaccine. This type of immunity is known as passive immunity. So, vaccination is extremely important to develop immunity in the body.

Q.2. What are the reasons for drug abuse? Suggest some of the preventive measures.

Ans: Though everyone knows it is extremely harmful to abuse drugs, some people still consume them and get addicted slowly. The reasons for their attraction towards drugs include the following:

  • Curiosity for drugs
  • Pressure from peers to consume drugs
  • To escape frustration, failure and other psychological problems
  • To enhance performance in physical activities

The measures mentioned below can be followed to prevent drug abuse:

  • Avoid the friends who pressurise others to consume drugs
  • Spreading awareness of the harmful effects of drugs
  • Seeking help from parents
  • Seeking the help of counsellors and medical experts.

Q.3. Write down the names of the causative agents of the diseases mentioned below.

Pneumonia, Typhoid, Common Cold, Ascariasis, Ringworm, Amebiasis

Ans. The causative of the diseases are as follows:

Diseases Causative Agents
Pneumonia Streptococcus
Typhoid Salmonella typhi
Common Cold Rhinovirus
Ascariasis Ascaris
Ringworm Microsporum species/Trichophyton species/Epidermophyton Species
Amebiasis Entamoeba histolytica

Very Long Answer Questions (5 Marks)

Q.1. Write a brief note on the role of lymphoid organs in the immune response. Elaborate on the different types of lymphoid organs in the human body with examples.

Ans. Lymphoid organs in the human body track microbes and foreign substances and stimulate an immune response against them. These organs can be divided into the following categories:

  1. Primary Lymphoid Organs: These organs produce the cells of the immune system. They are also known as central lymphoid organs. Bone marrow and Thymus come under this category.

(a) Bone Marrow: It is the main lymphoid organ that actively produces all types of blood cells including lymphocytes. It helps in the development and maturation of T lymphocytes and B lymphocytes by providing a micro-environment. The mature B cells travel to the circulatory system to detect the pathogens.

(b) Thymus: It is located beneath the breastbone near the heart. T lymphocytes are also produced and nurtured in the thymus. The thymus is large at the time of birth but keeps shrinking with age.

  1. Secondary Lymphoid Organ: They help the lymphocytes to interact with the antigen and destroy them.

(a) Spleen: It is a large bean-shaped organ that contains mainly lymphocytes and phagocytes. It is regarded as the graveyard of RBC. It acts as a filter for blood by trapping blood-borne microorganisms.

(b) Lymph Node: They are responsible for trapping the microorganisms and antigens that enter the lymph and tissue fluid. The lymphoid tissues located within major tracts are called mucosa-associated lymphoid tissue (MALT).

Q.2. Which protozoa cause malaria? Write a short note on the life cycle of the malarial parasite.

Ans. Plasmodium vivax is the protozoan that causes malaria.

This protozoan is a parasite, so it needs hosts for its growth and development. When a female Anopheles bites an infected person, the protozoa enter its body, and when it further bites someone else the sporozoites of the protozoa mixes up with his blood. Thus, the healthy man becomes infected by malaria protozoa. There are four variants of malarial protozoa, namely, Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae. 

The life cycle of the protozoa is discussed below.

  • The life cycle of Plasmodium protozoa in the human body involves four stages: pre-erythrocytic schizogony phase, erythrocytic schizogony phase, gametogenic phase, and exoerythrocytic schizogony phase.
  • The sporozoites of the protozoa are present in the salivary glands of Anopheles mosquitoes. These sporozoites are transmitted into human blood when they bite someone.
  • These sporozoites reach the liver of the infected man and multiply there quickly to develop schizonts that contain merozoites.
  • These merozoites are attracted by glycoproteins present in the red blood cells.
  • There they produce gametes and rupture the red blood cells.
  • The ruptured RBCs release toxic haemozoin that causes high fever and shivering.
  • The symptoms of malaria become prominent after the incubation period of nine to fourteen days, during which the patient does not feel any illness.
  • When a mosquito bites the malaria patient, it takes the gametes present in the blood.
  • The gametes are fertilised in the gut of the mosquito.
  • The newly formed sporozoites are stored in the salivary gland of the mosquito.
  • When this mosquito bites someone, it injects the sporozoites into the blood.  As a result, this cycle never ends. .

Class 12 Biology Chapter 8 Important Questions- Summary

Chapter 8 Class 12 Biology Important Questions cover all the important topics given in the NCERT book. In this set of Important Questions, students will learn what pathogens are, how they affect the health of human beings, and how some pathogens live in the human body itself and later affect it. Along with the names of diseases and their causes, students will also learn the concept of vaccination, which helps develop immunity. The different types of immunity, several organs that produce special kinds of cells to protect the body, the immune response system, etc. are all discussed in detail. Some of the diseases that are extremely important from the exam perspective are elaborately discussed in the next section.

Class 12 Biology Chapter 8 Important Questions- Summary
Types of Diseases

Disease can be defined as abnormal conditions of organisms, in which, the normal functions of their body are interrupted. Genetic defects, immunological problems, and unhealthy lifestyle can cause diseases. These diseases can be divided into two categories.

  • Congenital Diseases
  • Acquired Diseases

Congenital Diseases: These kinds of diseases are also called birth defects because they exist in individuals since their birth. Mutations of genes, chromosomal aberrations, and several environmental factors can cause congenital diseases. These diseases are transmitted from one generation to another through the genes present in chromosomes. Hemophilia, Turner’s Diseases, Colour blindness, Down Syndrome, etc. are the names of some congenital diseases.

Acquired Diseases: People get affected by this kind of disease during their lifetime. Malaria, cancer, conjunctivitis, etc. are some common examples of acquired diseases. This kind of disease can be infectious, non-communicable, deficiency-related, or allergic in nature.

  • Pathogens are organisms that cause and spread diseases. Viruses, bacteria, protozoa, fungi, worms, etc. are examples of pathogens.


Immunity is the ability of the body to fight against pathogens. Immunity can be categorised in the following manner:

  • Innate Immunity
  • Acquired Immunity

Innate Immunity: This kind of immunity is inherent in nature. There are four types of barriers that protect the body from pathogens. These are: physical barriers, physiological barriers, cellular barriers, and cytokine barriers.

Acquired Immunity: This type of immunity is developed when a person comes into contact with a pathogen for the first time and initiates a low-intensity primary response against the pathogen. When that person is affected by the same pathogen later, his body generates a strong secondary response and protects the body. This kind of immunity is called acquired immunity.

AIDS (Acquired Immuno- Deficiency Syndrome)

  • AIDS is caused by the HIV virus.
  • HIV stands for Human Immunodeficiency Virus.
  • It is a retrovirus because it contains RNA as its genetic material.
  • It generates viral DNA in the host through the enzyme reverse transcriptase.
  • The viral DNA gets multiplied in the host.
  • Then the DNA enters T-lymphocytes causing a rapid decrease in their number.


  • The normal cells of our body show contact inhibition property, that is, the inhibition of cell growth when the cells are in contact with other cells. Some cells lose this property and continue to multiply leading to formation of a mass of cells, called a tumour.
  • Tumours are of two types: benign and malignant.
  • In our body, the growth and differentiation of cells are highly controlled. These regulatory mechanisms break down completely in the case of malignant tumour cells.
  • The malignant tumour cells grow rapidly and damage the surrounding cells.
  • These tumours cause cancer.
  • Several specific genes, called cellular oncogenes, have been found in normal cells, which when activated under certain conditions may lead to the oncogenic transformation of cells.

Drugs and Alcohol Abuse

  • Some of the widely abused drugs include heroin, cannabinoids, and coca alkaloids.
  • The opioid drugs get stuck at the opioid receptors present in the CNS and GI tract.
  • Diacetylmorphine, a popularly known heroin or smack, is extracted from the latex of Papaver somniferum, a poppy plant, by morphine acetylation.
  • Cannabinoids affect the cannabinoid receptors in the brain.
  • Cannabinoids are obtained from Cannabis sativa plants.
  • The flower tops, resins, and leaves of the plants are used to prepare cannabinoids, such as marijuana, charas, hashish, ganja, and others.
  • Cocaine or coca alkaloid is obtained from a plant, found mostly in South America, Erythroxylum coca. 
  • Sportsmen often take cannabinoids to increase their performance, relax their muscles and decrease anxiety.
  • Doctors often prescribe drugs to relieve pain, treat depression and insomnia, etc. Morphine is one such drug.
  • The nicotine, an alkaloid, found in tobacco stimulates the adrenal gland to release adrenaline and nor-adrenaline hormones into blood circulation which raise blood pressure and increases heart rate.


Class 12 Biology Chapter 8 Important Questions help the students practise the relevant questions and precise answers on human health and disease. These questions have been selected by subject experts after a thorough analysis of the questions repeated  in the past years’ question papers. So, students do not have to worry about searching for reference material online for Biology or any other subject for last-minute preparation. They can refer to these notes, and utilise the valuable time to revise other chapters and practice questions from them to get the best possible results.

FAQs (Frequently Asked Questions)

1. Write down the name of the biological control agent widely used against mosquito larvae.

Gambusia fish is used as a biological control agent against mosquito larvae.

2. Name the cells that produce natural antibodies.

B-lymphocytes are the cells that produce natural antibodies.

3. Write the name of the causative agent of elephantiasis.

The name of the agent causing elephantiasis is Wuchereria Bancrofti.

4. Name the vector that causes Chikungunya.

Aedes albopictus and Aedes aegypti mosquitoes, are the species most frequently engaged in the transmission cycle  of Chikungunya disease. Both species have the ability to spread Zika and dengue fever viruses, as well as other mosquito-borne infections.