Humoral immunity:<\/strong><\/p>\nThe immune response, which involves the action of different B lymphocytes, like plasma cells, for producing antigen-specific antibodies and memory cells for neutralizing or eliminating toxins and pathogens in the blood and lymph is called humoral immunity.<\/p>\n
Mechanism of humoral immunity:<\/strong><\/p>\nHumoral immunity works for both primary and secondary immune responses. In primary response, B lymphocytes develop typical antibody-producing plasma cells. These cells produce antigen-specific antibodies. Antibodies work in the following four ways.<\/p>\n
1 Agglutination:<\/strong><\/p>\nBy this process, antibodies agglutinate pathogens into clusters, which are then collectively phagocytized by macrophages.<\/p>\n
2 Precipitation:<\/strong><\/p>\nSome antigen molecules are clamped by antibodies and are precipitated.<\/p>\n
3 Opsonisation:<\/strong><\/p>\nAntibodies form a covering on the antigens so that the phagocytic cells can ingest packed antigens.<\/p>\n
4 Neutralisation:<\/strong><\/p>\nCertain toxic antigens are detoxified and inactivated by the antibodies. In secondary response memory, B cells play a major role. These cells are produced during a primary immune response and remain stored in the secondary lymphoid tissues for keeping the immunological behavior of the pathogen in memory of the body’s immune system. In case of another attack, these cells help in the quick activation of the body’s immune system.<\/p>\n
Question 7. Write the differences between humoral immunity and cell-mediated immunity.<\/strong><\/p>\nAnswer:<\/strong><\/p>\nDifference between humoral and cell-mediated immunity:<\/strong><\/p>\n
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Question 8 Mention the roles of different T cells in the immune response. Mention the roles of different B cells <\/strong>in immune response.<\/strong><\/p>\nAnswer:<\/strong><\/p>\nRoles of different T cells:<\/strong><\/p>\nDifferent T cells or T lymphocytes play different roles in the immune response of the body.<\/p>\n
They are as follows:<\/strong><\/p>\n1. Cytotoxic T cells or T cells kill the infected cell, to destroy antigen-carrying pathogens within it.
\n2. Helper T cells or T cells enhance the activity of killer cells (a type of T cells), antibody-producing B cells, and phagocytic macrophages.
\n3. Suppressor T cells or T cells destroy T cells, TH cells, and B cells to stop immune response after the elimination of the antigens.<\/p>\n
Roles of different B cells:<\/strong><\/p>\nDifferent B cells or B lymphocytes play different roles in the immune response of the body.<\/p>\n
They are as follows:<\/p>\n
1. Plasma cells originated from B cells produce specific antibodies to inactivate antigens.
\n2. Memory B cells remain in lymph glands, keeping the nature of antigens in memory, and taking quick action in case of any further attack.<\/p>\n
WBBSE Life Science And Environment Class 9 Solutions<\/strong><\/p>\nQuestion 9 Briefly describe the mechanism of the immune response against viral attack in the human body.<\/strong><\/p>\nAnswer:<\/strong><\/p>\nMechanism of the immune response against a viral attack:<\/strong><\/p>\nThe immune response is a complex process involving various cells and biochemical components inside the body.<\/p>\n
The steps of the immune response against the viral antigen are as follows:<\/strong><\/p>\n1. As any virus reaches the blood or attacks any body cells, large phagocytic macrophages engulf those infected cells. Soon viral antigens appear on the cell surface of macrophages.
\n2. High concentration of viral antigens on macrophage activates helper T lymphocytes in the blood.
\n3. Helper T cells immediately initiate the production of cytotoxic killer T cells, memory T cells, and B lymphocytes.
\n4. B lymphocytes proliferate very fast to produce plasma cells and memory B cells.
\n5. Plasma cells produce specific antibodies to bind and inactivate the virus before they get a chance to infect a cell.
\n6. Killer. T cells destroy the infected body cells along with viruses.
\n7. T and memory B cells stay in the body to recognize the same pathogen in case of further infection and to develop a quicker response.<\/p>\n
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Question 10 Mention the differences between B cells and T cells.<\/strong><\/p>\nAnswer:<\/strong><\/p>\nDifferences between B cells and T cells:<\/strong><\/p>\n
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WBBSE Life Science And Environment Class 9 Solutions<\/strong><\/p>\nQuestion 11. Write the differences between primary immune response and secondary immune response.<\/strong><\/p>\nAnswer:<\/strong><\/p>\nDifference between primary immune response and secondary immune response:<\/strong><\/p>\n
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Question 12. Give a brief historical account of the discovery of the smallpox vaccine.<\/strong><\/p>\nAnswer:<\/strong><\/p>\nDiscovery of smallpox vaccine:<\/strong><\/p>\nThe scientific concept of vaccination was developed in the later half the of 18th century when a number of scientists and physicians were working hard to develop a vaccine against smallpox, the most deadly and contagious disease of that time.<\/p>\n
Scientists noticed that most individuals, who once suffered from cowpox safely bypassed smallpox. But the search was on for long 25 years. Then Dr. Edward Jenner (1798) broke through the concept of vaccination.<\/p>\n
He collected a little pus from a cowpox vesicle on the hand of Sarah Nelmes, a milkmaid, and introduced it into the arm of James Phipps, an eight year old boy. After two months, the boy was inoculated with the smallpox virus, but he did not develop the disease.<\/p>\n
The modern concept of vaccination is standing in this story. After this discovery, the practice of vaccination took the correct route. After a long battle for about two centuries, smallpox has now been eradicated from the world.<\/p>\n
Question 13. What is a vaccine? Mention the basic working principles of vaccines to develop immunity in the body.<\/strong><\/p>\nAnswer:<\/strong><\/p>\nVaccine:<\/strong><\/p>\nThe vaccine is an antigenic material that is prepared with killed or weakened pathogens, part of pathogens, bacterial toxins, or microbial proteins, which do not cause illness but provide active acquired immunity against those pathogens when introduced into the body.<\/p>\n
Working principle of vaccines:<\/strong><\/p>\nBy vaccination, a killed germ, attenuated (weakened) germ, toxoids (toxins collected from germs) or subunits (fragments of proteins from germs) are introduced into the body of an individual. These may be injected or administered orally.<\/p>\n
As soon as the substance enters the body, antigens present in it, activate the immune system and initiate an immune response. T cells and B cells take a little time to inactivate such little quantity of antigens and this process is known as primary immune response.<\/p>\n
However, in this case, the main function is done by memory B cells. These cells, produced during the immune response, are retained in lymph nodes such as the spleen, thymus, etc. for a long time.<\/p>\n
In case of any future infection by the same germ, these memory cells recognize those antigens instantly and inactivate or destroy the attacker very fast. This process is recognized as a secondary immune response. Thus, a successful vaccination immunizes a person effectively.<\/p>\n
WBBSE Class 9 Life Science Solutions<\/strong><\/p>\nQuestion 14. Give a brief account of different types of vaccines.<\/strong><\/p>\nAnswer:<\/strong><\/p>\nTypes of vaccines:<\/strong><\/p>\nWith the development of science, new and advanced varieties of vaccines are being developed. Till date World Health Organization (WHO) has licensed vaccines for 25 diseases.<\/p>\n
Different types of vaccines are:<\/p>\n
1 Killed vaccine:<\/strong><\/p>\nThese vaccines contain killed pathogens. Vaccines of cholera, plague, and influenza are of this type.
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\n2 Live attenuated vaccine:<\/strong><\/p>\nBy some laboratory techniques virulence of the pathogens are reduced to prepare this type of vaccines. Vaccines of mumps, measles, and rubella (MMR vaccine) are of this type.<\/p>\n
3 Toxoid vaccine:<\/strong><\/p>\nThis type of vaccine is prepared by inactivated toxins from pathogens. Vaccines of tetanus and diphtheria are of this type.<\/p>\n
4 Conjugate vaccine:<\/strong><\/p>\nGenerally, the polysaccharide of the bacterial capsule is attached to a protein to prepare this vaccine. The body’s immune system can recognize this conjugated protein and keep it in memory for future immune responses. Vaccine against Haemophilus influenza<\/p>\n
5 Sub-unit vaccines:<\/strong><\/p>\nThis type of vaccine is prepared by small fragments of pathogenic protein. Vaccine against Hepatitis B is of this type.<\/p>\n
6 Heterotypic vaccine:<\/strong><\/p>\nThis is prepared by pathogens, causing disease to other animals but less or non-virulent to humans. Vaccines of smallpox and tuberculosis are of this kind.<\/p>\n
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WBBSE Class 9 Life Science Solutions<\/strong><\/p>\nQuestion 15. Mention briefly about the nature, symptoms, and mode of transmission of some human diseases.<\/strong><\/p>\nAnswer:<\/strong><\/p>\nDescription of some human diseases:<\/strong><\/p>\n
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Question 16 Explain the importance of hand washing. Write the components use in washing.<\/strong><\/p>\nAnswer:<\/strong><\/p>\nImportance of hand washing:<\/strong><\/p>\n1 Reducing the number of infections:<\/strong><\/p>\nHand washing can prevent about 30% of diarrhea-related sicknesses and about 20% of respiratory infections (e.g. common cold, meningitis, flu, hepatitis A) and most types of infectious diseases.<\/p>\n
2 Reducing child death:<\/strong><\/p>\nAbout 1.8 million children under the age of 5 die every year from pneumonia and diarrhea-related diseases. Washing hands carefully and thoroughly can help children and childcare providers stay healthy.<\/p>\n
3 To remove dirt:<\/strong><\/p>\nRemoving dirt through hand washing may even help prevent skin and eye infections.<\/p>\n
Components used in washing:<\/strong><\/p>\n1 Water:<\/strong><\/p>\nPure distilled water is the main component used in hand washing.<\/p>\n
2 Soap and Detergent:<\/strong><\/p>\nWater is not efficient for cleaning skin because fats and proteins which are components of organic oil are not readily dissolved in water. Removal of micro-organisms from the skin may be enhanced with the use of soaps and detergents.<\/p>\n
3 Hand antiseptic:<\/strong><\/p>\nHand sanitizers containing a minimum of 60% to 70% alcohol are and efficient germ killer.<\/p>\n
4 Shampoo:<\/strong><\/p>\nShampoos that contain selenium are effective in controlling dandruff. Dandruff is caused owing to fungal infection on the scalp.
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\n5 Thimerosal:<\/strong><\/p>\nAn organic compound containing mercury can be used for disinfection of skin and instruments.<\/p>\n
6 Wipes:<\/strong><\/p>\nHand washing with wipes is also recommended by CDC (Centers for Disease Control and Prevention). This washing is convenient during traveling when water and soap will not be available.
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\n7 Toothpaste and mouthwash:<\/strong><\/p>\nIt is used in brushing teeth and washing mouth.
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\n8 Disinfectant:<\/strong><\/p>\nPhenyl, bleaching powder is applied in our surroundings to keep the environment clean.<\/p>\n
WBBSE Class 9 Life Science Solutions<\/strong><\/p>\nQuestion 17. Why and when should an individual wash their hands? Write down the proper method of washing hands.<\/strong><\/p>\nAnswer:<\/strong><\/p>\nReason of washing hands:<\/strong><\/p>\nWe take food with hand. We often touch our lips, face, and nose with our hands. By contaminated hands, germs or toxins may enter our body through the mouth, eyes, and nose. Therefore, one must wash the hands to stay healthy.<\/p>\n
Time of washing hands:<\/strong><\/p>\nHands must be washed before:<\/strong><\/p>\n1. Taking food
\n2. Cooking
\n3. Serving food
\n4. feeding and attending to a baby or a patient.<\/p>\n
Proper washing of hands is a must after using the toilet, cleaning raw vegetables, fish, and meat, attending to a patient, sweeping and cleaning rooms and toilets, polishing shoes and tying shoe-laces, checking the air pressure of the cycle tire, coming home from outside, etc.<\/p>\n
The proper method of washing hands:<\/strong><\/p>\nThe proper method of washing hands is mentioned below:<\/strong><\/p>\n1. Wet your hands with clean water.
\n2. Take liquid hand-wash or soap in wet hands and rub it for one or two minutes to make rich foam.
\n3. Carefully rub in between all fingers.
\n4. Place the hands under running water and continue rubbing until the foam clears.
\n5. Close tap with a clean cloth and wipe the hand with a dry and clean towel.<\/p>\n
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Question 18 Write a short note on the ‘WASH’ program of UNICEF. ‘WASH’ program of UNICEF<\/strong><\/p>\nAnswer:<\/strong><\/p>\nThe percentage of healthy children in a population is the index of development of a nation. But it is unfortunate that even in the 21st century, millions of children suffer from diarrhea and several other water-borne diseases.<\/p>\n
This happens because of contaminated water, which occurs mostly due to a lack of proper sanitation. 44% of the global population defecates in open areas. Feces contain numerous germs, which easily contaminate water, especially during the rainy season.<\/p>\n
In view of that, UNICEF (United Nations International Children’s Emergency Fund) has developed a global strategy to lift the standard of health of school children by providing them with adequate drinking water, infrastructure for proper sanitation, and a sense of hygiene.<\/p>\n
This program is popularly known as ‘WASH’ (Water Sanitation Hygiene Programme). United Nations has set a goal for sustainable development of the standard of living of the world population in this millennium.<\/p>\n
To reach the target, UNICEF has developed a strategy to maximize child survival rate by providing access to adequate drinking water, and sanitation facilities to schools all over the world along with education and nutrition.<\/p>\n
WBBSE Class 9 Life Science Solutions<\/strong><\/p>\nQuestion 19 Describe the WASH strategy taken by UNICEF to improve hygiene behavior among school children. How can the WASH program be made successful?<\/strong><\/p>\nAnswer:<\/strong><\/p>\nWASH strategy to improve hygiene behavior among school children:<\/strong><\/p>\nSchools are the places where a child spends most of the time of his or her life all through the development period. So UNICEF has developed the plan to make every school a child-friendly place.<\/p>\n
In view of that UNICEF has extended both monetary and strategic support to all developing countries of the world to develop infrastructure for child-friendly schools. The strategy to enhance child survival and development, UNICEF has encouraged a three-pillar approach.<\/p>\n
The first is enabling a child-friendly environment in the school. Next is to improve hygiene behavior among the students and the third one is to build infrastructure for water supply and sanitation services.<\/p>\n
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Points to make WASH successful:<\/strong><\/p>\nThe points to make WASH successful are as follows:<\/strong><\/p>\n1. Wash your hands with adequate water and soap before taking food and after using Three pillar approach of WASH toilets.
\n2. Always use sanitary toilets.
\n3. Clean raw fruits and vegetables before consuming.
\n4. Keep a close vigilance on drinking water sources to reduce contamination to zero.
\n5. Clean water storage containers every day.
\n6. Keep your domestic and school toilets clean.
\n7. Clip your nails regularly and do not let any filth to deposit under it.<\/p>\n
Question 20. Mention different hygienic practices to secure the good health of a person as well as of society.<\/strong><\/p>\nAnswer:<\/strong><\/p>\nDifferent types of hygienic practices:<\/strong><\/p>\nThe conditions or practices helpful to maintain health and to prevent diseases, especially through cleanliness are known as hygiene. Hygiene can be practiced in three different levels, i.e., personal, household, and social levels, which are mentioned below.<\/p>\n
1 Personal level hygiene:<\/strong><\/p>\n1. Cleaning hands before taking food, after using the toilet, and handling any unclean material.
\n2. Brushing teeth after taking a meal and before going to bed.
\n3. Taking a bath once or twice a day.
\n4. Trimming hair and clipping nails regularly.<\/p>\n
2 Household level hygiene:<\/strong><\/p>\n1. Washing and sun-drying clothing and bedding at regular intervals.
\n2. Cleaning utensils, kitchen equipment, raw vegetables, fish, and meat.
\n3. Cleaning toilets, basins, and sinks.
\n4. Cleaning and disinfecting water reservoirs.<\/p>\n
3 Social level hygiene:<\/strong><\/p>\n