CBSE Class 12 Biology Human Health And Diseases Worksheet Set C

Very Short Answer Questions

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

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: 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.

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

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

Short Answer Questions

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: 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: 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. 

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

(b) Active and passive immunity: 

Question: Name and explain the two types of immune responses in humAnswer. 
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: 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: 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: Identify a, b, c and d in the following table: 

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

Long Answer Questions

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.
Answer. (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: Name the form of Plasmodium that gains entry into the human body. Explain the different stages of its life cycle in the human body. 
Answer. 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. 
Answer. 
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: 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 humAnswer.
(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. 
Answer. Amoebic dysentery (Amoebiasis)
- It is caused by a protozoan endoparasite, Entamoeba histolytica, found in large intestine of humAnswer.
- 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) 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.
Answer. (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: 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?
Answer. B-cells and T-cells belong to the category of lymphocytes, i.e., leucocytes (WBC).
Differences between B-lymphocyte and T-lymphocyte

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. 
Answer. (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: (a) Cancer is one of the most dreaded diseases of humAnswer. 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 orgAnswer.
(d) Why are cancer patients often given α-interferon as part of the treatment?
Answer. (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.

Question: Why do some adolescents start taking drugs? How can the situation be avoided?
Answer. 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: What is the basic principle of vaccination? How do vaccines prevent microbial infections?
Name the organism from which hepatitis B vaccine is produced. 
Answer. 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 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.
Answer. 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: 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.
Answer. (a) Yes. Because these may be abused by sports person.
(b) Cannabis (sativa)
(c) Cannabinoids effect cardiovascular system of the body.

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.
Answer. (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 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.
Answer. (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