Human Health and Diseases Exam Questions Class 12 Biology

Please see Chapter 8 Human Health and Diseases Exam Questions Class 12 Biology below. These important questions with solutions have been prepared based on the latest examination guidelines and syllabus issued by CBSE, NCERT, and KVS. We have provided Class 12 Biology Questions and answers for all chapters in your NCERT Book for Class 12 Biology. These solved problems for Human Health and Diseases in Class 12 Biology will help you to score more marks in upcoming examinations.

Exam Questions Chapter 8 Human Health and Diseases Class 12 Biology

Objective Questions

Question. Which of the following is the symptom for pneumonia?
(a) Sustained high fever
(b) Problems in respiration
(c) Mucus and blood in stools
(d) Both (a) and (b)

Question. Which of these following is not a bacterial disease of human?
(a) Typhoid
(b) Diptheria
(c) Pneumonia
(d) Dysentery

Question. In common cold which of the following body part is not affected
(a) Nose
(b) Lungs
(c) Respiratory tract
(d) All a,b,c is infected

Question. The pathogen for malaria
(a) Plasmodium –bacteria
(b) Plasmodium – virus
(c) Plasmodium -Protozoan
(d) None of these

Question. Malignant malaria is caused by
(a) Plasmodium vivax
(b) Plasmodium malaria
(c) Plasmodium falciparum
(d) All of these

Question. The infectious form of malarial pathogen enters the human body through
(a) Male anopheles mosquito bite
(b) Contaminated food and water
(c) Droplet discharged by the infected person while sneezing
(d) None of these

Question. In liver the malarial parasite reproduces
(a) Asexually producing gametocytes
(b) Does not reproduce in liver
(c) Asexually reproduces
(d) None of these

Question. During malarial infection the cause of chills and high fever reoccuring every 3-4 days is due to
(a) Liver infection by sporozoites
(b) RBC infected by plasmodium
(c) Haemozoin released by rupture of RBC during infection
(d) None of these

Question. Malarial parasite requires which of the following host to complete its life cycle
(a) Human
(b) Mosquito
(c) House fly
(d) Both (a) and (b)

Question. Amoebiasis is caused by
(a) Bacteria
(b) Virus
(c) Protozoa
(d) Helminthes

Question. Blood circulation was discovered by
(a) Robert cook
(b) William Harvey
(c) T.H Morgan
(d) None of these

Question. Deficiencies with which a child is born and defects which the child inherits from parents from birth are known as?
(a) Genetic disorders
(b) Mental disorder
(c) Speed disorder
(d) None of these

Question. State the incorrect one
(a) Health simply means absence of disease or physical fitness
(b) Health is state of complete mental and social well being
(c) Unhealthy people are less efficient at work
(d) Health increases longevity of people

Question. Yoga is good for
(a) Physical health
(b) Mental health
(c) Both (a) and (b)
(d) None of these

Question. State the incorrect statement
(a) Maintenance of hygienic food and water resources are necessary for achieving good health
(b) When functioning of one or more organs or system of the body is adversely affected we are not healthy
(c) Diseases which are easily transmitted from person to other are non – infectious disease
(d) AIDS is an infectious disease

Question. Which of the following is a/are disease causing organism/s?
(a) Bacteria
(b) Fungi
(c) Helminths
(d) all of these

Question. State the incorrect statement
(a) Most of the parasites who harm the host by living inside them are pathogens
(b) Pathogens result in morphological and functional damage to host
(c) Pathogen need not to adapt to life within the environment of host
(d) Bacteria, viruses and fungi are also pathogens

Question. Typhoid is caused by
(a) Streptococcus typhi
(b) Salmonella typhi
(c) Plasmodium
(d) None of these

Question. Typhoid symptoms does not include
(a) Sustained high fever
(b) Stools with excess mucous and blood clots
(c) Weakness
(d) Headache

Question. Which of the following pathogen is responsible for pneumonia?
(a) Plasmodium
(b) Streptococcus pneumonia
(c) Hemophilus influenzae
(d) Both (b) and (c)

Very Short Answer Questions

Question. Name the two intermediate hosts which the human liver fluke depends on to complete its life cycle so as to facilitate parasitization of its primary host. 
Ans. Snail and Fish

Question. When does a human body elicit an anamnestic response? 
Ans. At the time of secondary response.

Question. How does haemozoin affect the human body when released in blood during malarial infection?
Ans. Haemozoin is responsible for the chill and high fever recurring every three to four days during malarial infection.

Question. State the functions of mast cells in allergy response. 
Ans. Mast cells release chemicals like histamine and serotonin in allergic response.

Question. What is the mechanism by which the AIDS virus causes deficiency in the immune system of the infected person?
Ans. The virus enters macrophages after getting into the body of individual where RNA forms viral DNA by reverse transcription. The viral DNA gets incorporated in the host cell’s DNA and directs the infected cells to produce viral copies. The newly produced virus particles attack helper T-cells and thus the number of T-cells decrease. Since the helper T-cells are essential for functioning of immune system, the person suffers from various diseases due to deficient immune system.

Question. State two different roles of spleen in the human body. 
Ans. Spleen is the secondary lymphoid organ that stores lymphocytes, it filters microbes and acts as a reservoir to store erythrocytes (Any two).

Question. Name any two physiological barriers that provide innate immunity? 
Ans. Acid in stomach/saliva in mouth/tears in eyes. (Any two)

Question. How is a cancerous cell different from a normal cell?
Ans. (i) There is no adherence in cancerous cell whereas normal cells remain adhered to one another.
(ii) Tumour is formed in cancerous cells due to repeated uncontrolled cell division whereas it is absent in normal cells.
(iii) Cancerous cells have no definite lifespan but normal cells have definite lifespan and old cells are replaced by new cells.

Short Answer Questions

Question. List the symptoms of ascariasis. How does a healthy person acquire this infection?
Ans. Symptoms of ascariasis: Internal bleeding, muscular pain, anaemia, blockage of intestinal passage.
A healthy person can acquire this infection by intake of water, vegetables/fruits/foods
contaminated with eggs of the parasite.

Question. Why an immunosuppressive agent is taken after an organ transplant?
Ans. Our immune system is capable to differentiate between ‘self’ and ‘non-self’ cells/tissues. The graft (grafting) is a non-self tissue which may be rejected by our immune system. So, to prevent the rejection, immunosuppressants are taken after the transplant.

Question. Name the causative organism of the disease amoebiasis. List three symptoms of the disease.
Ans. Entamoeba histolytica causes amoebiasis.
Symptoms are constipation, abdominal pain/cramps, stool with excess mucous/blood clots.

Question. Identify a, b, c and d in the following table: 

S.No.	Name of the human disease	Name of the causal bacteria/virus	Specific organ or its part affected
(i)	Typhoid	Salmonella typhi	a
(ii)	Common cold	b	c
(iii)	Pneumonia	Streptococcus pneumoniae	d

Ans. (a) small intestine (b) Rhino virus
(c) nose and respiratory passage (d) alveoli of lungs

Question. Identify A, D, E and F in the diagram of an antibody molecule given below:

Ans. A—Antigen binding site D—Light chain
E—Heavy chain F—Disulfide bridge.

Question. Name the host and the site where the following occur in the life-cycle of a malarial parasite:
(a) Formation of gametocytes]
(b) Fusion of gametocytes
Ans. 

	Host	Site of occurrence
(a) Formation of gametocytes	Human	Red blood cells
(b) Fusion of gametocytes	Anopheles mosquito	Intestine

Question. A student on a school trip started sneezing and wheezing soon after reaching the hill station for no explained reasons. But, on return to the plains, the symptoms disappeared. What is such a response called? How does the body produce it?
Ans. Such a response is called allergic reaction or allergy. On exposure to allergens like dust, pollens,etc., chemicals like histamine and serotonin are released from the mast cells, resulting in an allergic response.

Question. Differentiate the following and give examples of each:
(a) Innate and acquired immunity
(b) Active and passive immunity
Ans. (a)

S.No.	Innate immunity	Acquired immunity
(i)	It is present from birth and is inherited from parents.	It is not present from the birth.
(ii)	It is non-specific.	It is pathogen specific.
(iii)	The various physical, physiological, cellular, cytokine barriers are the basis of innate immunity.	The memory cells formed by B and T-cells are the basis of acquired immunity.
(iv)	The innate immunity remains throughout life.	The acquired immunity can be short-lived or life long.

(b) Active and passive immunity: Refer to Table 8.1.

S.No.	Active immunity	Passive immunity
(i)	It is developed due to contact with pathogen (dead or living) or its antigen, that leads to production of antibodies in the host body.	It is developed when readymade antibodies are injected into the body to protect body against foreign agents.
(ii)	It has no or only few side effects.	It may cause a reaction.
(iii)	It is slow but long lasting.	It is fast but lasts only for few days.
(iv)	It takes time to develop its response.	It is used when the immune response has to be faster.
(v)	For example, vaccination for polio, etc.	For example, administration of tetanus antitoxins, antibodies in colostrum, etc.
(vi)	Injecting microbes deliberately during immunisation or infections organisms entering body induce active immunity.	Foetus receives some antibodies from their mother through placenta during pregnancy,which induce passive immunity.

Question. Name and explain the two types of immune responses in humans. 
Ans. The two types of immunity are active immunity and passive immunity.
Active immunity: Immunity developed in the host body due to production of antibodies in response to antigens.
Passive immunity: When ready-made antibodies are directly given to protect the body against foreign agents.
OR
The two types of immunity are humoral immunity and cell-mediated immunity.
Humoral immunity: Immune responses given by antibodies found in the blood.
Cell-mediated immunity: Activation of T-lymphocytes mediate this immunity.
OR
The two types of immunity are primary immunity and secondary immunity.
Primary immunity: When our body encounters a pathogen for the first time, it produces primary response.
Secondary immunity: Subsequent encounter with the same pathogen generates highly intensified secondary response or secondary immunity.

Question. If a regular dose of drugs or alcohol is not provided to an addicted person, he shows some withdrawal symptoms. List any four such withdrawal symptoms.
Ans. The withdrawal symptoms are:
(a) Anxiety (b) Shakiness
(c) Nausea (d) Sweating

Question. List the two types of immunity a human baby is born with. Explain the differences between the two types. 
Ans. The two types of immunity a human baby is born with are innate and passive/acquired immunity.
Innate immunity is a non-specific type of defence that provides barrier to the entry of antigens.

Passive immunity is a pathogen-specific type of defence in which readymade antibodies are directly given to protect body against foreign agents. The foetus receives antibodies through the placenta.

Long Answer Questions

Question. Mention the name of the causal organism, symptoms and the mode of transmission of the disease amoebiasis. 
OR
(a) Name the protozoan parasite that causes amoebic dysentery in humans.
(b) Mention two diagnostic symptoms of the disease.
(c) How is this disease transmitted to others?
OR
(a) Name the agent that causes amoebiasis and the human body organ that it infects.
(b) Write the symptoms and the mode of transmission of the disease. 
Ans. Amoebic dysentery (Amoebiasis)
• It is caused by a protozoan endoparasite, Entamoeba histolytica, found in large intestine of humans.
• Housefly acts as mechanical carrier and transmits the parasite from faeces of infected person to the food.
• Infection takes place through food and water contaminated by faecal matter.

Question. A doctor prescribed morphine as a sedative and pain killer to your cousin who had undergone surgery. Even after recovery, he craved for the prescribed medicine. What do you conclude about his condition, had he continued with the same medication? After appraising yourself, what measures will you suggest to him to overcome this problem? Briefly explain any two.
Ans. His condition is drug dependence. It is the tendency of the body to manifest a characteristic and unpleasant withdrawal syndrome if regular dose of drugs is abruptly discontinued. Because of perceived benefits, drugs are frequently used repeatedly from which the person may not be able to get out.
Following measures can be taken to overcome this problem:
(i) Education and counseling to face problems and stresses and to channelise the energy into healthy pursuits like reading, music, yoga and other extracurricular activities.
(ii) Seeking help from parents to guide the person appropriately and immediately.
(iii) Seeking professional and medical help to the person to get rid of the problem completely with sufficient efforts and will power a(ny two).

Question. Name the form of Plasmodium that gains entry into the human body. Explain the different stages of its life cycle in the human body. 
Ans. Plasmodium vivax gains entry into the human body.
Malaria
• It is caused by a protozoan Plasmodium (P. vivax, P. malaria and P. falciparum).
• P. falciparum causes the most serious and fatal malignant malaria.
• The vector of Plasmodium is female Anopheles mosquito which transfers the sporozoites (infectious form).
• Treatment is by antimalarial drugs like quinine, chloroquin.
• Malaria can be prevented by killing mosquitoes by spraying DDT, BHC, etc., and using insect repellents, mosquito nets, etc.

Question. Malarial parasite ‘Plasmodium’ completes its life cycle in two hosts. Draw its complete life cycle and explain various stages it follows throughout its life. 
Ans. Refer to Fig. 8.1. (Img 299)
Stages:
(a) The stage in which the parasite enters in the body of humans through saliva of mosquito—sporozoite stage.
(b) Asexual reproduction of sporozoites in liver cells, resulting into bursting of those cells and releasing outside into the blood.
(c) Sporozoites infect RBCs, cause them to get burst and represented by repeated cycles of fever.
Released parasites also infect other RBCs.
(d) Parasites then follow sexual stage in RBCs which is called as ring signet stage and appears as a ring inside the RBCs under microscope. Usually presence of malarial parasite in humans is identified by pathologists by this stage.
(e) Female mosquito takes up gametocytes with the blood of host. Fertilisation and development takes place in the intestine of mosquito.
(f) From intestine, parasite comes to the salivary glands from where it reaches to human body and that is how the cycle continues.

Question. Under polio prevention programme, infants in India were given polio vaccines on a large scale at regular intervals to eradicate polio from the country.
(a) What is a vaccine? Explain how does it impart immunity to the child against the disease.
(b) With the help of an example each, differentiate between active and passive immunity.
Ans. (a) Vaccination is the process of introduction of weakened or inactivated pathogens or proteins (vaccine) into a person to provide protection against a disease.
• Vaccines are weakened or inactivated pathogens or proteins introduced into a person to provide protection against a disease.
• Immunisation is the process by which the body produces antibodies against the vaccine (primary response) and develops the ability to neutralise pathogens during actual infection (secondary response).
• Vaccination provides immunisation after a time gap.
• Vaccination and immunisation are based on the property called ‘Memory’ of the immune system.
(b) Refer to Basic Concepts Point 9.

Question. To which category of cells do B-cells and T-cells belong? How do they differ from each other with reference to their formation and response to antigens?
Ans. B-cells and T-cells belong to the category of lymphocytes, i.e., leucocytes (WBC).
Differences between B-lymphocyte and T-lymphocyte

S.No.	B-lymphocytes	T-lymphocytes
(i)	They mature in bone marrow.	They mature in thymus gland.
(ii)	They produce antibody against antigen.	They directly attach the antigen or direct B-cells to produce antibody.
(iii)	They do not respond to organ transplantation.	They respond to organ transplantation.

Question. Explain the process of replication of a retrovirus after it gains entry into the human body.
OR
(a) How does a Human Immunodeficiency Virus (HIV) replicate in a host?
(b) How does a HIV-infected patient lose immunity?
(c) List any two symptoms of this disease. 
Ans. (a)

(b) An HIV-infected patient loses immunity due to loss of T-lymphocytes.
(c) Symptoms are fever, diarrhoea, susceptibility to other diseases and prone to microbial infection. (Any two)

Question. Your school has been selected by the Department of Education to organise and host an interschool seminar on “Reproductive Health—Problems and Practices”. However, many parents are reluctant to permit their wards to attend it. Their argument is that the topic is “too embarrassing.”
Put forth four arguments with appropriate reasons and explanation to justify the topic to be very essential and timely. 
Ans. (i) The issue of puberty and adolescence need to be addressed effectively with the respective age group because many changes take place in the body during adolescence of which they are supposed to be aware of.
(ii) To bring in awareness about their reproductive health and its effect on their physical,emotional and social being.
(iii) To address the increase in sex abuse and sex crimes in our country.
(iv) Myths and misconceptions related to reproductive issues need to be cleared at the right time.

Question. Why do some adolescents start taking drugs? How can the situation be avoided?
Ans. The psychological attachment to certain effects such as euphoria and temporary feeling of well-being,associated with drugs and alcohol is called addiction.
QU People take drugs/alcohol when not needed, but with repeated use, tolerance level of receptions in body increases; receptors thus respond to higher doses, leadinng to greater intake and addition.
For measures to avoid taking drug, Avoid undue pressure: Every child has his own choice and personality and hence should be respected and nurtured accordingly. They should not be forced to perform beyond their threshold limits, be in sports or studies, etc.
QU Educating and counselling: Children should be educated and counselled to face problems, stresses,to accept disappointments and features as part of life. We shold put in efforts to channellise child’s energy into healthy pursuits like sports, reading, music, yoga etc.

Question. (a) Name and explain giving reasons, the type of immunity provided to the newborn by the colostrum and vaccinations.
(b) Name the type of antibody
(i) present in colostrum
(ii) produced in response to allergens in human body.

Ans. (a) Colostrum provides passive immunity, because the infant gets antibodies from the mother’s body directly for protection.
Vaccinations provide active immunity because in this case microbes are injected into the body do develop immunity slowly.
(b) (i) IgA (ii) IgE

Question. What is the basic principle of vaccination? How do vaccines prevent microbial infections?
Name the organism from which hepatitis B vaccine is produced. 
Ans. Principle of vaccination is based on the property of ‘memory’ of immune system. In vaccination,a preparation of antigenic proteins of pathogens or inactivated/live but weakened pathogens is introduced into the body. The antigens generate primary immune response by producing antibodies along with forming memory B-cells and T-cells. When the vaccinated person is attacked by the same pathogens, second time/subsequent time the existing memory B-cells and T-cells recognise the antigen and overwhelm the invaders with massive production of lymphocytes and antibodies. Hepatitis B vaccine is produced from yeast.

Question. (a) Why is there a fear amongst the guardians that their adolescent wards may get trapped in drug/alcohol abuse?
(b) Explain ‘addiction’ and ‘dependence’ in respect of drugs/alcohol abuse in youth.
Ans. (a) Adolescents are easily affected by (or are vulnerable to) peer pressure. Curiosity, need for adventure and excitement, and experimentation constitute common causes for motivation. A child’s natural curiosity motivates him/her to experiment. Television, movies, newspapers, internet also promote drug use.
(b) Addiction is the psychological attachment to certain effects such as euphoria or temporary feeling of well-being.
Dependence is the tendency of the body to show withdrawal syndrome or symptoms if regular doses of drug/alcohol is abruptly discontinued.

Question. (a) Name the types of lymphoid organs, lymph nodes and thymus are. Explain the role played by them in causing immune response.
(b) Differentiate between innate immunity and acquired immunity. 
Ans. (a) Thymus is primary lymphoid organ and lymph nodes are secondary lymphoid organs.
Thymus provides the microenvironment for immature lymphocytes to differentiate into antigen-sensitive lymphocytes.
Lymph nodes serve to trap the microorganisms or other antigens, which happen to get into the lymph and tissue fluid. Antigens trapped in the lymph nodes are responsible for the
activation of lymphocytes present there and cause the immune response.
(b)

Question. A team of students are preparing to participate in the interschool sports meet. During a practice session you find some vials with labels of certain cannabionoids.
(a) Will you report to the authorities? Why?
(b) Name a plant from which such chemicals are obtained.
(c) Write the effect of these chemicals on human body.
Ans. (a) Yes. Because these may be abused by sports person.
(b) Cannabis (sativa)
(c) Cannabinoids effect cardiovascular system of the body.

Question. (a) Name and explain giving reasons, the type of immunity provided to the newborn by the colostrum and vaccinations.
(b) Name the type of antibody
(i) present in colostrum
(ii) produced in response to allergens in human body.
Ans. (a) Colostrum provides passive immunity, because the infant gets antibodies from the mother’s body directly for protection.
Vaccinations provide active immunity because in this case microbes are injected into the body do develop immunity slowly.
(b) (i) IgA (ii) IgE

Question. (a) Cancer is one of the most dreaded diseases of humans. Explain ‘Contact inhibition’ and ‘Metastasis’ with respect to the disease.
(b) Name the group of genes which have been identified in normal cells that could lead to cancer and how they do so?
(c) Name any two techniques which are useful to detect cancers of internal organs.
(d) Why are cancer patients often given α-interferon as part of the treatment?
Ans. (a) Contact inhibition is the property of normal cells in which contact with other cells inhibits their uncontrolled growth.
Metastasis is the property in which tumour cells reach distant sites in the body, through blood.
(b) Proto oncogenes or Cellular oncogenes.
These genes when activated under certain condition could lead to oncogenic transformation of the cells.
(c) Biopsy/radiography/CT/MRI (Any two)
(d) α-interferon activates immune system and destroys the tumour.