CBSE Class 12 Biology Human Health And Diseases Worksheet Set D

Question. Describe the asexual and sexual phases of life cycle of Plasmodium that cause malaria in humans. 
Answer. Life cycle of Plasmodium requires two hosts for completion, such a two host life cycle is called digenetic.
I. Life cycle of Plasmodium in Man - Asexual phase
(i) Infective stage of Plasmodium is sporozoite. When the mosquito bites another human, sporozoites are injected with bite.
(ii) Parasites (sporozoites) reach the liver through blood.
(iii) The parasite reproduces asexually in liver cells, bursting the cells and releasing into the blood.
(iv) Parasites enter the red blood cells (RBCs) and reproduce asexually there bursting the red blood cells and causing cycles of fever and other symptoms. Released parasites infect new red blood cells.
(v) Sexual stages develop in RBCs.
II. Life cycle of Plasmodium in female anopheles mosquito - Sexual phase
(i) Female mosquito takes up gametocytes with blood meal.
(ii) Fertilisation and development take place in the mosquito’s stomach.
(iii) The zygote elongates and becomes motile called ookinete.
(iv) The ookinete moves and bores through the wall of the stomach of female Anopheles mosquito. The ookinete changes to oocyst on the surface of the stomach.
(v) Inside the oocyst, sporozoites are formed which are released in the body cavity of the mosquito.
(vi) Mature infective stages (sporozoites) move to different organs of the body cavity but many of them penetrate salivary glands of mosquito.
(vii) When the female Anopheles mosquito bites a healthy person, the sporozoites are injected in his/ her blood alongwith saliva.

Question. How do cytokine barriers help in evading viral infections? 
Answer. Interferons are cytokine barriers. These are low molecular weight proteins secreted by virus infected cells, which protect non-infected cells from further viral infection.

Question. In what way is monocyte a cellular barrier with reference to immunity? 
Answer. Monocytes are motile and phagocytic leucocytes. They engulf bacteria and cellular debris and constitute cellular barriers of innate immunity.

Question. Why is colostrum a boon to the newborn baby?
Answer. Colostrum (mother’s first milk) is rich in IgA antibodies. It provides passive immunity to new born and protects it from various diseases.

Question. Name any two types of cells that act as ‘cellular barriers to provide innate immunity in humans.
Answer. Certain types of leukocytes (WBCs) like polymorphonuclear leukocytes (PMNL- neutrophils) and natural killer cells in the blood are cellular barriers, which provide innate immunity in humans.

Question. Why is secondary immune response more intense than the primary immune response in humans? 
Answer. Secondary immune response is quicker and more intense than the primary immune response because the memory B cells are present to quickly deal with the invading microbes by forming antibodies. Body “remembers” that it previously encountered this type of infection.

Question. What is an autoimmune disease? Give an example.
Answer. Autoimmune disease is a condition in which body’s immune system attacks self-cells. E.g., rheumatoid arthritis.

Question. When does a human body elicit an anamnestic response? 
Answer. Human body elicits an anamnestic response (secondary response) to the subsequent encounter with the same pathogen to which the body had previously encountered (primary response).

Question. State two different roles of spleen in the human body. 
Answer. Spleen is the secondary lymphoid organ. It is the site where proliferation and differentiation of B and T lymphocytes takes place and in fetus, spleen produces all types of blood cells.

Question. How do interferons protect us?
Answer. Virus infected cells produce an antiviral protein called interferon which on reaching the nearby infected cells, make them resistant to viral infection.

Question. What is it that prevents a child to suffer from a disease he/she is vaccinated against? Give one reason. 
Answer. Vaccine is suspension or extract of weakened (attenuated/ dead) pathogens of disease which when injected into healthy person provides it active acquired immunity to the disease.
Vaccination stimulates the antibody production and formation of memory cells without causing the disease. This protects the child by neutralising the pathogenic agents during infection.

Question. Some allergens trigger sneezing and wheezing in human beings. What causes this type of response by the body?
Answer. Sneezing and wheezing in human beings to some allergens is caused due to exaggerated response of the immune system.

Question.  A boy of ten years had chicken-pox. He is not expected to have the same disease for the rest of his life. Mention how it is possible. 
Answer. A body when encounters a pathogen (in this case chicken pox) for first time produces antibodies, that results in memory of the first encounter to protect the body in future from the same disease.

Question. What role do macrophages play in providing immunity to humans? 
Answer. Macrophages are phagocytic cells that remove bacteria or other foreign bodies from blood or tissues and display their antigen to alert the lymphocytes and stimulate them.

Question. It was diagnosed by a specialist that the immune system of the body of a patient has been suppressed. Name the disease the patient has been suffering from and its causative agent.
Answer. In immunodeficiency diseases, the immune system of the body gets weakened, leading to repeated microbial infections. The patient is suffering from AIDS (Acquired Immune deficiency Syndrome) caused by HIV (Human Immunodeficiency Virus).

Question. Name an allergen and write the response of the human body when exposed to it. 
Answer. Pollen grain is an allergen. Exposure to pollen causes hay fever. It is the form of allergy due to pollen of grasses, trees and other plants. It is characterised by inflammation of the membrane lining the nose and sometimes of the conjunctiva. The symptoms are sneezing, running nose and watering eyes due to histamine release.

Question. Differentiate between active and passive immunity. 
Answer. The given table shows differences between active and passive immunity:

Active immunity	Passive immunity
It is developed when the person’s own cells produce antibodies in response to infection or vaccine.	It is developed when antibodies produced in other organisms are injected into a person to counter act antigen such as snake venom.
It provides relief only after long period.	It provides immediate relief.
It has no side effects.	It may cause reaction.
It is long lasting.	It is not long lasting.

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? 
Answer. Hill station and plains do have different weather conditions and environment. Sneezing and wheezing on hill station is due to exposure to different allergens, this response is called allergy. It is a hypersensitive response of a person to foreign substance coming in contact with or entering the body. Allergy involves IgE antibodies and release of chemicals like histamine and serotonin from mast cells.

Question. A young boy when brought a pet dog home started to complain of watery eyes and running nose. The symptoms disappeared when the boy was kept away from the pet.
(a) Name the type of antibody and the chemicals responsible for such a response in the boy.
(b) Mention the name of any one drug that could be given to the boy for immediate relief from such a response. 
Answer. (a) Such a response in the boy is called allergy which occurs due to production of IgE antibodies and chemicals like histamine and serotonin from the mast cells.
(b) Anti-histamine could be given to the boy for immediate relief from such a response.

Question. A student on a school picnic to a park on a windy day started sneezing and having dificulty in breathing on reaching the park. The teacher enquired whether the student was allergic to something.
(a) What is an allergy?
(b) Write the two unique characteristics of the system involved in the response observed in the student. 
Answer. (a) Allergy is a hypersensitive response to foreign substances, coming in contact with or entering the body. It is characterised by sneezing, watery eyes, difficulty in breathing etc.
(b) Two unique characteristics of system involved in allergic response are :
(i) The body will produce Ig E antibodies
(ii) The body will release chemicals like histamine and serotonin from the mast cells.

Question. How does a vaccine for a particular disease immunise the human body against that disease?
Answer. Vaccine is a preparation of dead/weakened germs of a disease which on inoculation into healthy person provides temporary/permanent active/ passive immunity by inducing antibody formation. The antibodies produced in the body against these antigens would neutralise the pathogenic agents during actual infection. The vaccines also generate memory B and T cells that recognise the pathogen quickly on subsequent exposure and attack the invaders with a large production of antibodies.

Question. Write the events that take place when a vaccine for any disease is introduced into the human body.
OR
Why is a person with cuts and bruises following an accident administered tetanus antitoxin?
Give reasons. 
Answer. In vaccination, a preparation of antigenic proteins of pathogens or weakened pathogen is introduced into the body. These antigens generate the primary immune response, and the memory B and T cells. When the vaccinated person is attacked by the same pathogen again, the existing memory T or B cells recognise the antigen quickly and attack the invaders with massive production of lymphocytes and antibodies.
OR
A person with cuts and bruises following an accident has chances of getting infected from tetanus. So, in this case quick immune response is required which is provided by giving the patient tetanus antitoxin which is a preparation containing preformed antibodies to the toxin.

Question. (a) Highlight the role of thymus as a lymphoid organ.
(b) Name the cells that are released from the above mentioned gland. Mention how they help in immunity. 
Answer. (a) Thymus is a primary lymphoid organ where the maturation of T-lymphocytes takes place. Thymus atrophies with age.
(b) T-lymphocytes are released from thymus. T cells provide cell-mediated immunity and defend against pathogens including protists and fungi that enter the cells.

Question. Name and explain the two types of immune responses in humans. 
Answer. Immune response is the specific reactivity induced in a host by an antigenic stimulus. It is of two types - primary and secondary immune response.
(i) The reaction of the body’s immune system to the first attack of microbes (antigens) is called primary immune response. It takes much longer time to develop because of the requirement of suitable receptor development. This response is feeble and declines rapidly. This produces both receptors and memory cells.
(ii) The reaction of the body’s immune system to any subsequent infection of the same microbe is termed secondary immune response. It is quicker and more intense than primary immune response because memory B cells present quick response against invading microbes.

Question. Name the two types of immune systems in a human body. Why are cell mediated and humoral immunities so called?
Answer. Two types of immune systems in human body are : Antibody Mediated Immune System (AMIS) and Cell Mediated Immune System (CMIS). Antibody-mediated (or humoral) immunity is associated with the appearance of antibodies, secreted by B-lymphocytes, in the extracellular fluids such as plasma, lymph and external secretions. Cell-mediated immunity is mediated by T-lymphocytes that defend against pathogens including protists and fungi that enter the cells.

 

 

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. 
Answer. Snail and Fish

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

Question. How does haemozoin affect the human body when released in blood during malarial infection?
Answer. 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. 
Answer. 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?
Answer. 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. 
Answer. 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? 
Answer. Acid in stomach/saliva in mouth/tears in eyes. (Any two)

Question. How is a cancerous cell different from a normal cell?
Answer. (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?
Answer. 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?
Answer. 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.
Answer. 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

Answer. (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:

Answer. 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
Answer. 

	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?
Answer. 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
Answer. (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. 
Answer. 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.
Answer. 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. 
Answer. 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.

Question. Identify A, B, C and D in the replication of HIV (retrovirus).

Answer. (A) Reverse transcription.
(B) Viral DNA incorporates into host genome.
(C) New viral RNA produced by infected cell.
(D) New viruses can infect other cells.

1. In the immune system, interferons are a part of
(a) physiological barriers
(b) cellular barriers
(c) physical barriers
(d) cytokine barriers.

2. The letter T in T-lymphocytes refers to
(a) tonsil
(b) thalamus
(c) thymus
(d) thyroid

3. Use of anti-histamines and steroids gives a quick relief from
(a) allergy
(b) nausea
(c) cough
(d) fever

4. The immunoglobulin abundant in colostrum, is
(a) Ig D
(b) Ig A
(c) Ig G
(d) Ig M

5. Diacetyl morphine is commonly known as
(a) cocaine
(b) hashish
(c) ganja
(d) heroin

6. Opium is extracted from
(a) Atropa belladona
(b) Papaver somniferum
(c) Erythroxylum coca
(d) Cannabis sativa

7. The disease chikungunya is transmitted by
(a) houseflies
(b) Aedes mosquitoes
(c) cockroach
(d) female Anopheles

8. Anti venom against snake poison contains
(a) antigens
(b) antigen-antibody complexes
(c) antibodies
(d) enzymes

9. Which of the following glands is large sized at birth but reducies in size with aging?
(a) Pineal
(b) Pituitary
(c) Thymus
(d) Thyroid

10. The substance produced by a cell on viral infection that can protect other cells from further infection is
(a) serotonin
(b) colostrum
(c) interferon
(d) histamine

11. Many diseases can be diagnosed by observing the symptoms in the patient. Which group of symptoms are indicative of pneumonia?
(a) Difficulty in respiration, fever, chills, cough, headache
(b) Constipation, abdominal pain, cramps, blood clots
(c) Nasal congestion and discharge, cough, sorethroat, headache
(d) High fever, weakness, stomach pain, loss of appetite and constipation

12. Transplantation of tissues/organs to save certain patients often fails due to rejection of such tissues/organs by the patient. Which type of immune response is responsible for such rejections?
(a) auto-immune response
(b) humoral immune response
(c) physiological immune response
(d) cell-mediated immune response

13. ______ mosquitoes are the vectors of dengue and chikungunya.

14. ______ barriers protect the non-infected cells from further viral infections.

15. Cell-mediated immunity is provided by ______ .

16. Among non-infectious diseases, ______ is the major cause of death.

17. ______ test is performed to confirm typhoid.

18. Plasmodium enters the human body as ______ .

19. ______ is the toxin released by the rupture of RBCs into the blood in a malariainfected person.

20. _____ is the filarial worm.

21. ______ are the physical, chemical and biological agents that cause cancer.

22. Heroin is obtained by _______ of morphine.

 

23. Match the organisms (Pathogens) in Column I with the diseases they cause in Column II.

 

A. Rhino vims                     1. Ringworm

B. Plasmodium                    2. Filariasis

C. Salmonella                     3. Common cold

D. Trichophyton                  4. Typhoid

E. Wuchereria                     5. Malaria

                                         6. Amoebiasis

 

24. Match the items in Column I with those in Column II.

 

A. Physiological barrier             1. Interferons

B. Cytokine barrier                   2. Skin of the body

C. Cellular barrier                     3. Tear in the eyes

D. Physical barrier                    4. Antibodies in colostrum

                                              5. Polymorpho-nuclear leucocyte

 

25. Humoral immunity is responsible for rejection of organ transplants. [True/False]

 

26. a-interferon activates the immune system and help to destroy the tumour cells. [True/False]

 

27. Cannabinoids affect the digestive system. [True/False]

 

28. Nicotine, the alkaloid in tobacco causes the hallucinogenic effect. [True/False]

 

29. Colostrum contains antibody IgA and provides passive immunity. [True/False]

 

Directions (Q30 to Q33): Mark the odd one in each of the following groups.

 

30. Saliva in the mouth, Mucus coating in respiratory tract, Tear in the eyes, Acid in the stomach.

 

31. Thymus, spleen, appendix, tonsil.

 

32. Charas, Heroin, Marijuana, Hashish.

 

33. Typhoid, Pneumonia, Diphtheria, Malaria.

 

34. Who discovered blood circulation in humans?

 

35. Name one infectious and one non-infectious disease that is the major cause of mortality.

 

36. High fever, loss of appetite, stomach pain and constipation are some of the symptoms seen in a patient. How would the doctor confirm that the patient is suffering from typhoid and not amoebiasis?

 

37. Name one respiratory disease that infects the lung alveoli and one that does not infect the lungs.

 

38. Name two diseases that spread by droplet infection.

 

39. Name two diseases whose spread can be controlled by the eradication of Aedes mosquitoes.

Name two viral diseases transmitted by Aedes mosquito.

 

40. Name the stage of Plasmodium that gains entry into the human, when bitten by an infected female Anopheles. 

 

41. Trace the route of Sporozoite at Plasmodium, when it enters the human body through the bite of female Anopheles, till its entry into RBCs. 

 

42. Name the host where fertilisation occurs in the life cycle of Plasmodium 

 

43. How does malaria differ from chikungunya with reference to their vectors?

 

44. Malaria, typhoid, pneumonia and amoebiasis are some of the human infectious diseases. Which ones of these are transmitted through mechanical carriers? 

 

45. How does haemozoin affect the human body, when released in blood during malarial infection? 

 

46. Why is Gamhusia introduced into drains and ponds? 

 

47. What causes swelling of the lower limbs in patients suffering from filariasis?

 

48. What role do macrophages play in providing immunity to humans?

 

49. How do monocytes act as a cellular barrier in humans to provide innate immunity? 

 

 

In what way is monocyte a cellular barrier with reference to immunity? 

 

50. How do neutrophils act as a cellular barrier to pathogens in humans?