You can Download Chapter 8 Human Health and Disease Questions and Answers, 2nd PUC Biology Question Bank with Answers, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.
2nd PUC Biology Question Bank Chapter 8 Human Health and Disease
2nd PUC Biology Human Health and Disease NCERT Text Book Questions and Answers
What are the various public health measures, which you would suggest as a safeguard against infectious diseases?
The various public health measures that could provide safeguard against infectious diseases are:
- Disposal of garbage – There should be regular collection and transport of garbage to disposal sites.
- Drainage – Drains should be covered to reduce the chances of the multiplication of flies and mosquitoes. Any blockage must be immediately attended to.
- Isolation – A person suffering from an infectious disease should be segregated so that others do not catch an infection from him.
- Sanitation – Clean surroundings can prevent the spread of diseases. This includes proper disposal of waste and excreta, periodic cleaning and disinfection of water sources, and observing standard practices of hygiene in public catering.
- Eradication of vectors – It is necessary to eliminate the vectors and their breeding places. This can be achieved by – avoiding stagnation of water in and around residential areas.
- regular cleaning of household coolers.
- use of mosquito nets
- introducing fishes like Gambusia in ponds that feed on mosquito larvae.
- spraying of insecticides in ditches, swamps, and drainage areas.
- doors and windows should be provided with wire mesh.
- Vaccination and immunization – This has enabled us to completely eradicate a deadly disease like smallpox. A large number of other infectious diseases like polio, diphtheria, pneumonia, and tetanus have been controlled to a large extent by the use of vaccines.
- Pollution – Anti-pollution laws should be strictly enforced.
- Drinking water – Drinking water should be filtered and free from any contamination, suspended, and dissolved matter.
- Education – People should be educated about communicable diseases so that they can protect themselves against infection.
In which way has the study of biology helped us to control infectious diseases?
The study of biology helps us to diagnose the pathogen in the following ways:
- The life-cycle of many pathogens studied.
- Alternate and reservoir hosts are known.
- The mechanisms of transmission of the disease are known.
- The protective measures are suggested against disease and pathogens based on the above studies.
- Suitable medicines against infectious disease are suggested.
- The preparation of vaccines against many pathogens also entitles the use and study of biology.
How does the transmission of each of the following diseases take place?
- Amoebiasis is caused by Entamoeba – histolytica. Infection occurs by ingesting cysts with food and drinks. These cysts are carried by flies from faeces to food and drinks.
- Malaria is caused by Plasmodium sp. Malarial parasites are carried from the infected to the healthy person by the female Anopheles mosquito.
- Ascariasis in man is caused by ingesting food and water contaminated with Ascaris eggs. Children become infected by ingesting soil.
- Pneumonia is spread by sputum (containing Streptococcus pneumoniae) of the patient. These microbes are inhaled and get lodged in the bronchioles.
What measure would you take to prevent water-borne diseases?
To prevent water-borne diseases, the following measures are required :
- Drinking water should be clean, free from contamination. This could be achieved by filtration, boiling or sedimentation, and chemical treatment of water.
- Water resources/ reservoirs should be periodically de-contaminated / disinfected.
- Water should not be allowed to stand for long to become breeding pools.
- Standards practices of hygiene should be strictly maintained in public catering.
Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
Suitable genes refer to that gene (a specific segment of DNA), encoding a protein associated with the target infectious organism, is spliced into a plasmid, which is then copied & formulated as a vaccine.
Name the primary and secondary lymphoid organs.
Primary lymphoid organs are bone marrow and thymus. Secondary lymphoid organs are spleen, lymph nodes, tronsils, peyer’s patches of small intestine and appendix.
The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form:
- MALT – Mucosa-associated lymphoid tissue
- CMI – Cell-mediated immunity
- AIDS – Acquired Immune Deficiency Syndrome
- NACO – National AIDS control organization
- HIV – Human immunodeficiency virus
Differentiate the following and give examples of each:
(a) Innate and acquired immunity
(b) Active and passive immunity
(a) Innate and acquired immunity
|Present from birth||Develops during lifetime|
|Remains throughout life||Short or long life|
|Contact with antigen not necessary||Contact with antigen necessary|
|Is inheritable||Can be inherited for brief period to neonates|
|Prevents from disease contraction||Protects from pathogen and other members of some species.|
(b) Active and passive immunity
|Due to contact with the antigen||Obtain antibodies from outside|
|Not immediate||Develops immediately|
|Lasts for a sufficiently long time||Lasts for few days|
|Antibodies are produced by body
Side effects are few
|Antibodies obtained from outside.|
Draw a well-labelled diagram of an antibody molecule.
What are the various routes by which transmission of the human immunodeficiency virus takes place?
The various routes by which transmission of the human immunodeficiency virus (HIV) takes place are –
- Sexual contact with an infected person.
- Use of contaminated needles and syringes to inject drugs or vaccines.
- Use of contaminated razors.
- By transfusion of contaminated blood.
- From infected mother to her child through the placenta.
- Organ transplantation.
- Artificial insemination.
What is the mechanism by which the AIDS virus causes a deficiency of the immune system of the infected person?
After the entrance of the virus into the body of the person, the virus enters into macrophages where the RNA genome of the virus reverse transcribes to form viral DNA with the help of a reverse transcriptase enzyme. This viral DNA gets incorporated into the host cell’s DNA and directs the infected cells to produce viruses. The infected macrophages produce the virus and act as an HIV factory. Simultaneously, the HIV virus enters into helper T lymphocytes where it replicates and produces other viruses.
These viruses are then released into the blood and attack other helper T-lymphocytes. In this way, there occurs a progressive decrease in the number of helper T-lymphocytes in the body of the infected person. Due to a decrease in the number of helper T-lymphocytes, the patient becomes so immunodeficient that he/she is unable to protect himself/herself against the infections of bacteria, fungi, viruses etc.
How is a cancerous cell different from a normal cell?
Cancer cell is different from normal cells in the sense that it:
- Looses the property of contact inhibition.
- Continues to grow and divide.
- Produces masses of cells called tumours.
Explain what is meant by metastasis.
The non-regulated growth of the cells that accompanies cellular transformation produces tumours or neoplasms. Each tumour being the product of the proliferation of a single abnormal cell. Malignant tumour cells are cancer cells that spread to mid take up residence in neighbouring tissues – a condition called metastasis.
List the harmful effects caused by alcohol/ drug abuse.
The adverse effects of drugs and alcohol abuse are:
- Cirrhosis and fatty liver: The liver synthesises fat from alcohol. The extra fat lowers the production of enzymes and structural proteins. The liver becomes a storehouse of fat and the result is fatty liver. The fatty liver syndrome leads to cirrhosis where liver cells are replaced by fibrous tissues.
- Alcoholic polyneuritis: Alcoholism reduces appetite. This leads to water-soluble vitamin deficiency (B complex) and causes polyneuritis.
- Heart diseases: Alcoholism causes cardiovascular diseases, hypertension, etc.
- Amnesia: Partial or total memory loss.
- Ulcer and pancreatitis: Constant use of alcohol causes stomach ulcers and pancreatitis.
- Male impotence: Due to the loss of sexual drive and necrospermia (defective sperms).
- Foetal alcohol syndrome (FAS) or alcohol embryopathy: Alcohol abuse during pregnancy causes abnormal development of foetus.
- Family problems: Alcoholism affects the family and community life. It leads to the deterioration of moral and cultural standards. It also causes traffic accidents, violence and antisocial activities.
Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?
Yes, friends can influence a person to take alcohol/drugs. One can protect himself/ herself from such an influence by avoiding experimental use of alcohol/drug for curiosity, pleasure, adventure, and excitement, and avoiding the company of such friends
Why is it that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.
Curiosity, excitement and experimentation may sometimes drive the youngsters towards drug and alcohol abuse. Usually, the first use of drug or alcohol may be out of curiosity or experimentation. Gradually they start this habit to escape facing problems. Academic activities like examination may also sometimes compel them to take drugs or alcohol. Because of the addictive nature of drug and alcohol, and their perceived benefits like relief from stress, a person may try taking these to get rid of pressure, examination and competition-related stresses. Feeling of independence, insecurity, frustration, depression etc are also associated with drug and alcohol abuse.
In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
- Adventure and excitement
- Peer pressure
- Family history, i.e., unstable or unsupported family structure
- Frustration and depression
- Relief from pain
- Feeling of independence
- Television, movies, newspapers, and the internet also help to promote this perception.
2nd PUC Biology Human Health and Disease Additional Questions and Answers
2nd PUC Biology Human Health and Disease One Mark Questions
In the past Indian Ayurvedic system considered that the persons having black bile would have a fever.
a. Name the person who is considered the father of medicine.
b. What made the change in the belief of having black bile during fever?
c. Who was the person behind this discovery?
b. Discovery of blood circulation
c. William Harvey
Write the full form of HIV.
Human Immunodeficiency Virus.
What are pathogens?
The organisms which cause diseases in man are called pathogens.
Write the full form of ELISA.
Enzyme-linked Immunosorbent Assay.
An antigen-antibody reaction is a specific reaction. Justify your answer.
The antibodies are specific to antigens i.e., a particular antibody binds only with a particular antigen. This is also known as the lock and key mechanism seen in the enzyme reaction. The antigen-binding site in the antibody is made such that the same type of antigen can attach to it. The antigen-antibody reaction makes the antigen inactive.
What is the source of opium?
Prepare a poster against smoking to exhibit in your school.
Say no to smoking
- Burning of tobacco with paper produces more than 1000 chemicals.
- Passive smokers also get these 1000 chemicals.
- Causes lung cancer.
- Causes oral cancer
- Causes emphysema
- Causes heart attack
- Causes peptic ulcer
Name the harmful chemical component which is found in tobacco.
A dog bites his own master. Sometimes in the human body, this type of action takes place.
a. Name the disease.
b. Give examples for this disease.
a. Autoimmune disease
b. Rheumatoid arthritis (affecting the joints)
Myasthenia gravis (neuromuscular disease leading to muscle weakness)
Diabetes mellitus type 1 (destruction of beta cells of the pancreas)
Name the common fungal diseases that infect man.
Which disease is caused by the transmission of HIV?
Write the role of macrophages in providing immunity to humans. (Delhi 2008)
Macrophages are phagocytes and through phagocytes, they destroy the microbes.
Write the full form of LSD. (CBSE 1994)
D-Lysergic acid diethylamide
What are Psychotropic drugs? (CBSE 1995)
These are mood-altering drugs that selectively affect behaviour perception and mental activity of a person using them.
Where is Wuchereria found?
Filarial worms Wuchereria are found in lymph vessels.
Define the term vaccine.
A vaccine is a suspension of killed or alternated pathogenic macro organism or antigenic preparations made out of it which on administration provides immunity towards the pathogen.
What harm does AIDS cause in humans?
The immune power of the body is decreased by AIDS.
Define Addiction. (HS&B 2001)
Addiction is the state of giving up to a drug, alcohol, or tobacco due to becoming physically, physiologically, and psychologically attached to its certain effects like euphoria and a temporary feeling of well-being.
What is immunity? (HS&B 2003)
Immunity is a natural or acquired ‘resistance of an individual to the development of pathological condition even after having received an infective dose of virulent pathogen its taxis or allergies.
Name 2 major groups and of cells required in attaining specific immunity. (CBSE 2005)
What is the full form of NAC?
National Aids Control Organization.
What is interferon?
Interferon is the proteins produced by virus-infected cells in our body.
Name combine form of the poppy, morphine, herein pethidine, and methedrine.
Give 2 examples of passive immunity.
- The antibodies IgA in colostrum
- Antibodies received by the foetus through the placenta.
Name the cells which are multiplied by HIV when it enters the human body.
Macrophages and helper T-lymphocytes.
While 2 features of acquired immunity.
- It is pathogen-specific
- It is characterized by memory.
Name 2 types of cells in which HIV multiplies after gaining entry into the human body.
Macrophages and Helps T cells.
Why is the bone marrow considered the main lymphoid tissue of our body?
Because in bone marrow along with blood cells lymphocytes are produced.
Which viruses have responsible for cancer?
Oncogenic viruses have cancer-causing viral oncogenes.
Enzyme-linked Immuno-sorbent assay.
What are primary lymphoid organs?
The primary lymphoid organs are those organs in which B-lymphocytes and T- lymphocytes undergo maturation, e.g., Bone marrow and thymus.
When is a tumour is referred to as Malignant?
Malignant tumor is a mass of proliferating neoplastic cells, which spread to distant sites through body fluids to develop secondary tumors.
What is oncogenic virus?
The viruses which cause cancer are called oncogenic virus.
How does tobacco smoking cause oxygen deficiency in the body.
Smoking increases the carbon monoxide content of the blood that refuses.
What type of cells provide Innate immunity?
What is drug abuse.
When drugs are taken for a purpose other than their normal clinical use and in amounts concentrations or frequency that impairs one’s physical, physiological and psychological functions, it constitute drug abuse.
Write any 2 uses of morphine.
- Used as selective
- Used as painkiller especially in patients who have undergone surgery.
Name the phylum and disease caused by Wucheria Bancroft (CBSE 2005)
- Phylum – Nemathelminthes
- disease:- Elephantiasis (filaria)
2nd PUC Biology Human Health and Disease Short Answer Type Questions
Mention any 2 measures for prevention and control of alcohol and drug abuse among adolescents.
- Communication: An adolescent should be able to disuses problems in studies, games, friends etc. with parents who should also know all the friends of the child.
- Avoid undue pressure: The child should not be asked to perform beyond threshold limits whether in studies, sports or extracurricular activities.
In which parts of the body of the hosts do the following events in the life cycle of plasmodium take place? Name both the body parts and the host.
(b) Development of gametocytes
(c) Release of Sporozoites
(d) Asexual reproductions.
(a) Fertilization: Inside stomach/intestine of mosquito host.
(b) Development of Gamete cites:- In blood of human host.
(c) Release of sporozoites – In to the blood of human host
(d) Asexual Reproductions – Inside liver cells and-RBC’s of human host.
Write the specific symptoms of typhoid.
Name its causative agent. (AI – 2009)
Symptoms of typhoid:
- Sustained high fever
- Loss of appetite
- Stomach pain
- Headache and weakness
- Intestinal perforations severe cases may cause death causative agent of typhoid is Salmonella typhi.
What are allergens? What causes the allergy is produced?
Allergy is the condition of hypersensitivity of the body against certain substances or to a physical or chemical agent allergens. When the antigen-antibody reaction takes place in the body, it results in allergy. Sufficient antibodies will not be produced if lacking proper immune system. The allergens combine with the antibody-bound mast cells, which causes the cell to burst to release histamine. It results inflammatory responses in the body. The allergy may be caused by medicine, cosmetics, and other substances like, pollen grains, dust particles etc.
Write the symptoms of pneumonia.
- Fluid-filled alveoli
- Cough and headache
- The nails turns gray to bluish in the severe cause.
Name and explain the type of barrier of innate immunity where some cells release inteifetofts when infected.
- Cells infected by virus release interferons
- Interferons provide protection to noninfected cells from infection.
How do saliva and tear help to prevent bacterial infection?
Saliva and tear consists of lysozymes Lysosomes are enzyme which can digest the bacterial cell wall which helps to kill bacteria.
Why vaccination is important in immunity?
Vaccination is the process of introduction of weakened or inactivated pathogens or proteins (vaccine) into a person so, provide protection against the disease. Vaccination provides immunisation after a time gap. Due to immunisation our body produces antibodies against the vaccine and develops the ability to neutralise pathogens during actual infection. Nowadays different types of vaccine which gives in children like polio, tetanus, deptheria, pertusis, small pox etc.
Differentiate between primary response and secondary response.
|Primary response||Secondary response|
|The immune response that occurs at the first encounter of the body with antigen is called -primary immune response||The immune response that occurs at the second and subsequent, encounters of the body with the antigen is called secondary immune response|
|It declines rapidly||It is severe and lasts for long time|
Differentiate between T lymphocyte and B- lymphocyte.
|T lymphocyte||B- lymphocyte.|
|These are lymphocyte which undergo maturation in thymus||Maturation undergo in bone marrow|
|They constitute cell-mediated immune and don’t produce antibodies||They constitute the humoral immune response and produce antibodies|
|They react to organ transplants||Don’t respond to organ transplants.|
How do B-lymphocyte cells direct humoral immunity?
The B-lymphocyte cells multiply in number in response to the attack by antigen. They start producing characteristics proteins called antibodies. These antibodies circulate in the body fluids and act against the pathogen/ antigens.
Describe the effect of alcohol on human body and society.
The effect of alcohol on the human body and society are:
- It effects the central nervous system.
- Persons is incapable of differentiating what is right and what is wrong.
- Taking excess of alcohol weakens heart, lungs, liver and other parts of the body.
- Pupil of eye expands on taking excess of alcohol.
- This increases the criminal activities of human beings.
Elst specific symptoms of amoebiases write its causative agent. (CBSE 2009)
Symptoms of amoebiasis
- The patient passes out blood and mucus with the stool.
- Severe griping pain in the abdominal, fever nausea, exhaustion and nervousness.
- In chronic case, intestinal wall punctures. The causative agent is Entamoeba histolytica.
Describe psychotropic drugs.
These drugs effect on thinking power, mental processes-, continuous use of these drugs, bring change in human behaviour, consciousness and perception. So, they are called mood-altering drugs. The person becomes addict by the use of these drugs and cannot live without these drugs.
AIDS is a disorder in which the immune mechanism of the body of a patient gets suppressed.
a. What pathogen is responsible for it?
b. Who discovered the pathogen for the first time?
c. Mention the major symptoms of that disorder.
a. HIV (Human Immunodeficiency Virus)
b. Prof. Luc Montagnier in 1983.
c. Fever, weight loss, diarrhea, enlargement of lymph glands. All these are due to low immune response.
What is Interferon?
Interferon: Interferon is an antiviral protein which is produced within animal cells due to stimulus produced after viral infection and which prevents the infection and, multiplication of other viruses.
(a) Explain the property that prevents normal cells from becoming cancerous
(b) All normal cells have inherent characteristics of becoming cancerous. Explain. (CBSE2009)
(a) Contact inhibition
(b) All normal cells have several genes called cellular oncogenes or proto-oncogenes.
These genes are activated under certain conditions can lead to oncogenic transformation of cells, i.e. cancer can result.
Write the importance of molecular biology in preventing cancer.
Techniques of molecular biology can be applied to detect genes in individuals with inherited susceptibility to certain cancers. Identification of such genes, which predispose individuals to certain cancers may be helpful in the prevention of cancer, such individuals are advised to avoid exposure to particular carcinogens to which they may be susceptible.
C – Change in bowel or bladder
A – A sore which does not heal
U – Unusual bleeding or discharge
T – Thickening or lump in the breast or elsewhere
I – Indigestion or difficulty in swallowing
O – Obvious change in wart or mole
N – Nagging cough
These are the symptoms of a disease.
a. Name the disease.
b. What is oncology?
c. What are oncogenes?
b. Study of cancer
c. Cancer inducing genes
Name one plant and the additive drug extracted from its latex. How does this drug affect the human body? (CBSE 2009)
Morphine is obtained from the plant Papaver somniferum (poppy plant).
It is an opioid that binds to specific receptors in the central nervous system and gastrointestinal tract and slows down body function.
Give four reasons to justify the intake of cannabinoids by sports person (A.I. 2008)
- Cannabinoids affect the cardiovascular system.
- They cause addiction and when the regular dose is not taken, there are unpleasant one’s term with drawl symptoms, which may be life-threatening.
- The person shows reckless behaviour vandalism and violence
- Excess can lead to coma and death due to heart failure cerebral hemorrhage etc.
2nd PUC Biology Human Health and Disease Short Answer Type Questions
Mention 3 major categories of factors that affect the health of a person.
Health is affected by
(i) genetic disorders:- the defects, deficiencies that are inherited from parents due to defective genes.
(ii) Infections caused by pathogens.
(iii) Lifestyles which includes
- Food and water (eating habits)
- Rest and exercise to the body
- Habits like drugs, alcohol etc.
How do normal cells get transformed into cancerous neoplastic cells? Mention the difference between viral oncogenes and cellular oncogenes (Foreign 2008)
The transformation of normal cells into cancerous neoplastic cells is induced by physical clinical and biological agents collectively called carcinogens, they lose the property of contact inhibition.
Differences between viral oncogenes and cellular oncogenes are
- Viral oncogenes are the genes present in I the oncogenic virus which affect the oncogenic transformation of the cells they infect.
- Cellular oncogenes are the genes presents in normal cells and code for growth factors, when activated under certain condition can cause the oncogenic transformation of the cell.
What are the side effects of the use of anabolic steroids by females?
The side effects in females includes
- Increased aggressiveness
- Abnormal menstrual cycle
- Excessive hair growth on the face and body
- Enlargement of elitoris
- Deepening of voice
- Mood swings and depression.
Give the side effects of the use of anabatic steroids in males.
The side effects in males includes
- Reduction in the size of testicles
- Decreased sperm productions
- Breast enlargement
- Premature baldness
- Enlargement of prostrate gland
- Development of acne.
(a) List any two situations when a medical doctor would recommend injection of performed antibodies into the body of a patient. Name this kind of immunisation
(b) Name the kind of immunity attained when instead of antibody weakend antigens are introduced into the body. (Delhi 2008)
(a) The two conditions include the following
- When a person is infected by a deadly microbe, for which an immediate immune response is required.
This kind of immunisation is called passive imminisation
(b) Active immunity.
Name the stage of plasmodium that a female Anopheles mosquito injects into a healthy person during its bite. Represent schematically the stages of the pathogen developed in the human body, till it is picked up by a mosquito.
(a) How are primary lymphoid organs different from secondary lymphoid organs. Give an example of each.
(b) Name any 4 types of cells involved in the cellular barriers of innate immunity.
- Primary lymphoid organs: These are the lymphoid organs where immature lymphocytes differentiate into antigen sensitive lymphocytes.
E.g. Bonemarrow, thymus.
- Secondary lymphoid organs: These are the lymphoid organs where the interaction occurs between lymphocytes and antigen and proliferation occurs.
E.g. Spleen, tonsil.
(b) The cell types are
- Poly morpho nuclear leucocytes (PMNL)
- Natural killer cells
2nd PUC Biology Human Health and Disease Five Marks Questions
The science club in your school has decided to organise a street play aiming at giving public awareness against AIDS.
a. Mention the important characters performing in this play.
b. State the major ideas you are going to convey through the play.
a. HIV, T-cells of the immune system, patient, other pathogens like
bacteria, viruses, protozoan etc.
b. i. Only one life partner in your life ii. Practise safe sex
iii. Use condoms
iv. Don’t share needles and syringes for injection.
v. Don’t receive blood from unknown person.
vi. Treatment is available to cure AIDS.
(i) Draw a labelled schematic diagram of antibody molecules
(ii) Mention any 4 warning signals of drug abuse in adolescents.
(ii) Warning signals of drug abuse:
Aggressive and rebellious behaviour Loss of appetite
Lack of interest in personal hygiene Drop in academic performance Change in sleeping and eating habits .
(i) Define innate immunity Mention any 2 ways in which it is accomplished in our body.
(ii) How does spleen functions as an organ of our immune system.
(i) Innate immunity is defined as the non¬specific type of defense with which an individual is bom and in always available to protect the body. It is accomplished by providing different types of barriers to the entry of antigens/pathogens
(a) Physical barriers: Skin of the body is the greater barrier that prevents the entry of microbes. Mucus coating on the epithelium of major tracts help in trapping the microbes that have entered the body.
(b) Physiological barrier:
- Saliva in the mouth and tear contain an anti-bacterial substance.
- HC1 scented by the stomach (C) Cytokine barriers:
Interferon are the proteins which are produced by the body cells in response to viral infection and they protect the non-infected cell from viral infection.
- Spleen acts as filter of blood by trapping the blood-borne microbes. It contains phagocytes which destroy the microbes through phagocytosis.
(a) Differentiate between active immunity and passive immunity.
(b) Describe the different methods of treatment of cancer.
|Active immunity||Passive immunity|
|When antibodies are produced by our β lymphocytes in response to the antigen, it is called active immunity.||When ready-made antibodies are injected into the body for defence, the immunity produced is called passive immunity.|
|It lasts for longer periods||It lasts for shorter period.|
(b) Different methods for the treatment of cancer are
- Surgery: The tumour cells are surgically removed to reduce the growth of cancerous cells.
- Radiation therapy: The tumour cells are radiated lethally taking care of the surrounding normal cells.
- Chemotherapy: Certain drugs are specific for particular tumors, but have side effects like anaemia, hair loss etc.
(a) Represent schematically the life cycle of HIV or Replication of Retrovirus.
(b) What are the various routes by which transmission of the human immunodeficiency virus takes place?
(b) The various ways of the transmission of ratio virus includes
- Sexual contact with infected persons
- By the transfusion of blood
- By the use of infected needles and syringes
- From infected mother to child through the placenta.
Why is using tobacco in any form injurious to health? Explain.
The burning tobacco and the paper produce more than 1,000 chemicals in the form of gases, vapours and particulates. The substances include nicotine, carbon monoxide, hydrogen cyanide, benzopyrene etc. Many of these are irritants and have toxic effects on the body. Tobacco is used for smoking and chewing. Its main stimulating component is nicotine, which causes addiction. Harmful effects of tobacco include lung cancer, oral cancer, emphysema, blood pressure variation, heart diseases, peptic ulcer etc.