Comprehensive CBSE Question Bank in Biology XII (Term-II)

CBSE II Question Bank in Biology CLASS 12 Features Short Answer Type Questions Long Answer Type Questions Strictly Based on the Latest CBSE Term-wise Syllabus Case Study Based MCQs Chapter at a Glance Very Short Answer Type Questions



Comprehensive CBSE Question Bank in Biology Term–II (For Class XII)



Comprehensive CBSE Question Bank in Biology Term–II (For Class XII) (According to the Latest CBSE Examination Pattern) By Dr. J.P. Sharma M.Sc., Ph.D., FISST Ex-Head, Deptt. of Botany Hindu College, Sonepat (M.D. University, Rohtak) Haryana   laxmi Publications (P) Ltd (An iso 9001:2015 company) bengaluru • chennai • guwahati • hyderabad • jalandhar Kochi • kolkata • lucknow • mumbai • ranchi new delhi

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Contents Chapters Pages Unit VIII Biology and Human Welfare 1–68 Chapter 1. Human Health and Diseases (NCERT Textbook Chapter-8)3–45 Chapter 2. Microbes in Human Welfare (NCERT Textbook Chapter-10)46–68 Unit IX Biotechnology and its Applications 69–116 Chapter 3. Biotechnology: Principles and Processes (NCERT Textbook Chapter-11)71–98 Chapter 4. Biotechnology and its Applications (NCERT Textbook Chapter-12)99–116 Unit X Ecology and Environment 117–172 Chapter 5. Organisms and Populations (NCERT Textbook Chapter-13)119–151 Chapter 6. Biodiversity and its Conservation (NCERT Textbook Chapter-15)152–172



Syllabus Class XII (Code N. 044) (2021-22) Term–II Theory EVALUATION SCHEME Marks Units 14 VIII Term–II 11 IX Biology and Human Welfare: Chapter – 8 and 10 10 X Biotechnology and its Applications: Chapter – 11 and 12 35 Ecology and Environment: Chapter – 13 and 15 Total THEORY TERM-II Unit-VIII Biology and Human Welfare Chapter-1: Human Health and Diseases Pathogens; parasites causing human diseases (malaria, dengue, chikungunya, filariasis, ascariasis, typhoid, pneumonia, common cold, amoebiasis, ring worm) and their control; Basic concepts of immunology–vaccines; cancer, HIV and AIDS; Adolescence–drug and alcohol abuse. Chapter-2: Microbes in Human Welfare Microbes in food processing, industrial production, sewage treatment, energy generation and microbes as bio-control agents and bio-fertilizers. Antibiotics; production and judicious use. Unit-IX Biotechnology and its Applications Chapter-3: Biotechnology–Principles and Processes Genetic Engineering (Recombinant DNA Technology). Chapter-4: Biotechnology and its Applications Application of biotechnology in health and agriculture: Human insulin and vaccine production, stem cell technology, gene therapy; genetically modified organisms–Bt crops; transgenic animals; biosafety issues, biopiracy and patents.

Unit-X Ecology and Environment Chapter-5: Organisms and Populations Organisms and environment: Habitat and niche, population and ecological adaptations; population interactions–mutualism, competition, predation, parasitism; population attributes–growth, birth rate and death rate, age distribution. Chapter-6: Biodiversity and its Conservation Biodiversity–Concept, patterns, importance; loss of biodiversity; biodiversity conservation; hotspots, endangered organisms, extinction, Red Data Book, Sacred Groves, biosphere reserves, national parks, wildlife, sanctuaries and Ramsar sites.

Unit VIII Biology and Human Welfare 1. Human Health and Diseases (NCERT Textbook Chapter-8) 2. Microbes in Human Welfare (NCERT Textbook Chapter-10)



Chapter-1 Human Health and Diseases (NCERT Textbook Chapter-8) Important Notes/Chapter at a Glance EARLY VIEW ABOUT HEALTH • Early Greeks like Hippocrates as well as Indian Ayurveda system considered health ‘a state of body and mind where there was a balance of certain humors (body fluids). • The discovery of blood circulation by Willium Harvey disapproved the good humor hypothesis of health. • Health is affected by the following factors: (i) genetic disorders—deficiencies with which a child is born and deficiencies/ defects which the child inherits from parents from birth; (ii) infections, and (iii) lifestyle including food and water we take, rest and exercise we give to our bodies, habits that we have or lack etc. What does Health Mean? • Health does not simply mean ‘absence of disease’ or ‘physical fitness’. • Health is defined as ‘a state of complete physical, mental and social well being’. Importance of Health • Health increases longevity of people and reduces infant and maternal mortality. • It increases productivity and brings economic prospenty. Factors Important to Maintain Good Health • The factors that are important to maintain good health are: — balanced diet — personal hygiene — regular exercise. • Good health can be achieved by the following: — awareness about diseases and their effect on different bodily functions — vaccination (immunisation) against infectious diseases. — proper disposal of wastes. — control of vectors — maintenance of hygenic food and water. Common Human Diseases • The condition, when the functioning of one or more organs or symptoms of the body is adversely affected, characterised by various signs and symptoms is called disease. • Diseases can be classified into two types: (i) Infectious Diseases and (ii) Non- infectious Diseases.

4 Biology-XII • Some of the infectious diseases like AIDS, Hepatitis-B are fatal. • Among non-infectious diseases, cancer is the major cause of death. Common Infectious Diseases • Depending upon pathogen, infectious diseases are as follows. Viral diseases, e.g., common cold, AIDS Bacterial diseases, e.g., Typhoid, Pneumonia Infectious diseases Protozoan diseases, e.g., Malaria, Amoebiasis Fungal diseases, e.g., Ringworm Helminthic diseases, e.g., Ascariasis, Elephantiasis (filariasis) — The disease causing organisms are called pathogens. — The pathogens can enter our body by various means, multiply and interfere with normal vital activities resulting in morphological and functional damage. • Bacterial Diseases (i) Typhoid Causative agent. It is caused by a pathogenic bacterium, Salmonella typhi. — The pathogen enters the small intestine through contaminated food and water and migrate to other organs through blood. Symptoms. The symptoms of typhoid include (a) sustained high fever (39° to 40°C) (b) weakness (c) stomach pain (d) constipation (e) headache and (f) loss of appetite. — Intestinal perforation and death may occur in severe cases. Test. Typhoid fever can be confirmed by widal test. • Mary Mallon nicknamed Typhoid Mary was a cook and a typhoid carrier, who continued to spread typhoid for several years through the food she prepared. (ii) Pneumonia Causative organism. It is caused by bacteria, Streptococcus pneumoniae and Haemophilus influenzae. Symptons. The bacteria infect the alveoli of lungs. — As a result the alveoli get filled with fluid leading to severe problems in respiration. — The symptoms of pneumonia include (a) fever (b) chills (c) cough and (d) headache. — In severe cases, the lips and finger nails may turn gray to bluish in colour. Transmission. Infection occurs by (a) inhaling the droplets/aerosols released by infected person (b) sharing glasses and utensils with an infected person. • Some other common bacterial diseases in man are—dysentry, plague, diphtheria, etc.

Human Health and Diseases 5 • Viral Diseases Common cold Causative organism. It is caused by a group of viruses called Rhinoviruses. — These viruses infect the nose and respiratory passage but not the lungs. Symptoms. The symptoms of common cold include (a) nasal congestion and discharge (b) sore throat (c) hoarseness (d) cough (e) headache (f) tiredness, etc., which last for 3–7 days. Infection/Transmission. The infection occurs by (a) cough or sneezes from infected person inhaled directly (b) through contaminated objects such as pens, books, cups, doorknobs, computer key board or mouse etc. • Protozoan Diseases (i) Malaria Causative organism. It is caused by different species of a tiny protozoan, Plasmodium, (P. vivax, P. malaria and P. falciparum), and are responsible for different types of malaria. — P. falciparum causes, the most serious, malignant malaria, which can even be fatal. Life cycle of Plasmodium — Plasmodium enters the human body as sporozoites (infectious form) through the bite of infected female Anopheles mosquito, which is the vector (transmitting agent of the disease). — The parasites initially multiply within the liver cells and then attach the Red Blood Cells (RBCs) resulting in their rupture. — The rupture of RBCs is associated with the release of a toxin called haemozoin, which is responsible for the chill and high fever recurring every three to four days. — When a female Anopheles mosquito bites an infected person, these parasites enter the mosquito’s body and multiply to form sporozoites that are stored in salivary glands of the mosquito. — When these mosquitoes bite a human, the sporozoites are introduced into his/ her body, initiating the events of malaria. — The malarial parasite requires two hosts—human and mosquitoes, to complete its life cycle. Control of Malaria. The diseases can be controlled by eradicating mosquitoes and avoiding mosquito bite by using mosquito repellents, mosquito nets, etc. (ii) Amoebiasis (Amoebic dysentry) Causative organism. It is caused by Entamoeba histolytica, a protozoan parasite in the large intestine. Transmission. Houseflies act as carriers and serve to transmit the parasite from faeces of infected person to food and food products, thereby contaminating them. — Drinking water and food contaminated by the faecal matter are the main source of infection.

6 Biology-XII Symptoms. The symptoms of this disease include (a) constipation (b) abdominal pain and cramps (c) stool with excess mucous and blood clots. • Helminthic Diseases (i) Ascariasis Causative organism. It is caused by a intestinal parasite, Ascaris (Round worm). Transmission. The eggs of the parasite are excreted along with faeces of infected persons which contaminate soil, water, plants etc. — A healthy person acquires this infection through contaminated water, plants etc. Symptoms. Symptoms of the disease include (a) internal bleeding (b) muscular pain (c) fever (d) anaemia and (e) blockage of intestinal passage. (ii) Filariasis/Elephantiasis Causative organisms. It is caused by the filarial worms, Wuchereria bancrofti and W. malayi. Symptoms. The parasite normally cause inflammation of the organs in which they live for many years, causing them to swell and look like the limbs of an elephant, hence called elephantiasis. — The genital organs are also often affected, resulting in gross deformities. Transmission. The pathogens are transmitted to a healthy person through the bite by the female mosquito (Culex mosquito) vector. • Fungal Diseases (i) Ringworms Causative Organisms. It is one of the most infectious diseases in man, caused by fungi like Microsporus, Trichophyton and Epidermophyton. — Heat and moisture help these fungi to grow especially in skin folds such as those in the groin or between toes. Symptoms. The symptoms include (a) dry scaly lesions on various parts of the body such as skin, nails and scalp. —  These lesions are accompanied by intense itching. Transmission. Ringworms are generally acquired from soil or by using towels, clothes or even the comb of infected individuals. Prevention and Control of Infectious Diseases Many infectious diseases can be prevented/controlled by following measures: (i) Maintenance of personal hygiene (i.e., keeping the body clean, consumption of clean food and water). (ii) Maintenance of public hygiene (proper disposal of excreta/wastes, periodic cleaning and disinfection of water reservoirs, observing standard practices of hygiene in public catering). (iii) Eradication of vectors and their breeding places (by avoiding stagnation of water in and around residential areas, regular cleaning of coolers, use of mosquito nets, spraying of insecticides in ditches, drainage, swamps etc., and introducing fishes like Gambusia in ponds that feed on mosquito larvae).

Human Health and Diseases 7 (iv) Such precautions can also prevent the wide spread incidences of the vector borne (Aedes mosquitoes) diseases like dengue and chikungunya. (v) Vaccination for diseases like polio, diphtheria, pneumonia, tetanus, etc. Immunity The overall ability of the host’s body to fight the disease causing organisms, conferred by the immune system is called immunity. • Innate Immunity — It is a non-specific type of defence, with which an individual is born. — It consists of different types of barriers to the entry of the foreign agents into our body. These barriers are: (i) Physical barriers — These barriers include skin and mucus coated epithelium of respiratory, gastro- intestinal and urinogenital tracts. — The skin prevents entry of the microbes, while the mucus coated epithelium traps microbes, entering our body. (ii) Physiological barriers — These barriers include (a) acid in the stomach (b) saliva in the mouth (c) tears from eyes that prevent microbial growth. (iii) Cellular barriers — These barriers include specialised cells, which phagocytose and destroy microbes. — These cells are leukocytes (WBC) of our body like (a) polymorpho-nuclear leukocytes (PMNL or neutrophils) (b) monocytes and (c) natural killer cells (a type of lymphocytes) cells in the blood, and macrophages in tissues. (iv) Cytokine barriers — These include interoferons (proteins) secreted by the virus infected cells which protect the non-infected cells from viral infection. • Acquired Immunity — It is the pathogen specific immunity. — It is acquired by a person during his/her lifetime either by contracting the disease or by vaccination. — When our body encounters a pathogen for the first time, produces a response called primary response, which is of low intensity. — Subsequent encounter with the same pathogen, produces a highly intensified response called secondary response, because the immune system has memory of the first encounter. — The primary and secondary immune responses are carried out with the help of B-lymphocytes and T-lymphocytes present in our blood. — B-lymphocytes produce specialised proteins called antibodies in response to pathogens to fight with them. — T-lymphocytes help B-lymphocytes to produce antibodies. — These antibodies are found in the blood and lymph hence their production is called as humoral immune response, and this type of immunity is called Antibody Mediated Immunity (AMI).

8 Biology-XII — T-lymphocytes produce cell mediated response and this type of immunity is Cell Mediated Immunity (CMI). • Antibodies — Antibodies are protein molecules called immunoglobulins (Igs). — Different types of antibodies produced in our body are IgA, IgM, IgE and IgG. — Each antibody molecule has four peptide chains, two small called light chains and two longer called heavy chains. — Hence, an antibody is represented as H2L2. • Active and Passive Immunity Acquired immunity is classified into two types: (i) Active immunity and (ii) Passive immunity. (i) A ctive Immunity. It develops due to immune response generated when a person suffers from a disease. It involves the active functioning of the person’s own immune system leading to the synthesis of antibodies and/or the production of immunologically active cells. (ii) P assive Immunity. It is conferred by the transfer of immune products like antibodies, etc., from another individual into a non-immune individual. — The colostrum secreted by mother during the initial days of lacation contains antibodies (IgA), provides passive immunity to the infants. — The foetus receiving some antibodies from their mother, through placenta, is another example of passive immunity. • Vaccination and Immunisation — The principle of immunisation or vaccination is based on the property of memory of the immune system. Vaccination. Vaccination is the process of introduction of a preparation of antigenic proteins of pathogen or inactivated/weakened pathogen (vaccine) into the body. — The vaccine generates antibodies that neutrilise the toxin/pathogen and also generate memory-B and T-cells that recognise the pathogen quickly on subsequent exposure and overwhelm the pathogen with massive production of antibodies. • Passive Immunisation — W hen a person is infected with some deadly microbes, requires a quick response as in the tetanus, the performed antibodies or antitoxin (a preparation containing antibodies to the toxin) is injected into the patient. It is called passive immunisation. — The antivenom injection given to the snakebite patients contain preformed antibodies, and is also an example of passive immunisation. • Vaccines and Recombinant DNA (r DNA) Technology — Now a days recombinant DNA (r DNA) technology is used in the production of antigenic polypeptides (antigens) of some pathogens in bacteria or yeast cells. — This approach allow a large scale production and greater availability of vaccines for immunisation.

Human Health and Diseases 9 e.g., Hepatitis-B vaccines are produced through r DNA technology in yeast cells. • Allergies — The exaggerated response or hypersensitive reaction of the immune system to certain antigens present in the environment is called allergy. — The substances/agents which produce an immune response are called allergens, e.g., mites in dust, pollens, animal dander, etc. — The antibodies produced in response to allergens are IgE type. Symptoms. The common symptoms of allergy are (i) Sneezing (ii) Watery eyes (iii) running nose and (iv) difficulty in breathing. — The symptoms of allergy are produced due to release of histamine and serotonin from the mast cells. Determination of cause of Allergy. The patient is exposed to injected with very small doses of possible allergens and the reactions are studied. Treatment. Drugs like anti-histamine, adrenalin and steroids quickly reduce the symptoms of allergy. Increasing incidence of allergies. The modern day life style and protected environment provided during early period of life, is resulting in lowering of immunity and more sensitivity to allergens in more and more children in metro cities. • Auto Immunity — The memory based acquired immunity evolved in higher vertebrates is based on the ability to differentiate foreign organisms (e.g., pathogens ) from self cells. — We still do not understand the basis of this, two corollaries of this ability have to be understood. (i) Higher organisms can distinguish foreign molecules as well foreign organ- isms. Most of the experimental immunology deals with this aspect. (ii) S ometimes due to genetic and other unknown reasons, the body attacks self cells. — It results damage to the body and is called auto immune disease, e.g., Rheumatoid arthritis, affecting many people. Immune System in the Body — The main functions of immune system are to recognise the foreign antigens, respond to these and keep a memory of them. — It also plays a role in allergic reaction, auto-immune diseases and organ transplantation. • Lymphoid Organs — These are the organs where origin and/or maturation and proliferation of lymphocytes take place. — Lymphoid organs are of two types: (i) Primary lymphoid organs and (ii) Secondary lymphoid organs. (i) Primary lymphoid organs — These are lymphoid organs where the immature lymphocytes differentiate into antigen sensitive lymphocytes. e.g., Bone marrow and thymus.

10 Biology-XII — B one marrow is the main lymphoid organ where all blood cells including lymphocytes are produced. — T hymus is located near the heart and beneath the breast bone; it is quite large at the time of birth but reduces to a very small size at puberty. — Both bone-marrow and thymus provide micro-environments for the development and maturation of T-lymphocytes. (ii) Secondary lymphoid organs — These are the lymphoid organs, where the lymphocytes after maturation are stored. — Spleen, lymph nodes, tonsils, Peyer’s patches of small intestine and appendix are the secondary lymphoid organs. • Spleen. It is a large bean shaped organ, mainly contains lymphocytes and phagocytes. — It acts as a filter of the blood and traps blood borne micro-organisms. — It also has a large reservoir of erythrocytes. • Lymph Nodes. These are small solid structures located at different points along the lymphatic system. — Lymph nodes serve to trap the microorganisms or other antigens, which reach to 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. Mucosal Associated Lymphoid (MALT) Tissue. The lymphoid tissue are also located within the lining of the major tracts (respiratory, digestive and urogenital tracts) called Mucosal Associated Lymphoid Tissue (MALT). — It constitutes about 50 per cent of the lymphoid tissue in human body. AIDS • The word AIDS stands for ‘Acquired Immuno Deficiency Syndrome’, means deficiency of immune system acquired during the lifetime of an individual. It is a group of infections/symptoms hence called syndrome. • It was first reported in 1981. • Causative Organism. AIDS is caused by a retrovirus called Human Immuno Deficiency Virus (HIV), which have an envelope enclosing the RNA genome. • Transmission. Transmission of HIV occurs by any of the following ways: (i) sexual contact with infected person (ii) transfusion of contaminated blood or blood products (iii) sharing infected needles as in the case of intravenous drug abusers, and (iv) from infected mother to her child through placenta. • High Risk Individuals. Following individuals are at high risk of getting the disease. (i) individuals who have multiple sexual partners (ii) drug addicts who take drugs intravenously

Human Health and Diseases 11 (iii) individuals who require repeated blood transfusions, and (iv) children born to an HIV infected mother. • How does HIV Make a Person Immuno Deficient — HIV after getting into the body of a person, enters into macrophages. — The RNA genome of the virus replicates to form viral DNA with the help of the enzyme reverse transcriptase. — This viral DNA gets incorporated into host cell DNA and directs the infected cell to produce virus particles. — The macrophages continue to produce virus, acting like a HIV factory. — HIV then enters the helper T-lymphocytes (TH), replicates and produce progeny viruses. — The progeny viruses released in the blood attach other helper T-lymphocytes and there is a progressive decrease in the number of helper T-lymphocytes in the body of the infected persons. — During this period, the person suffers from bouts of fever, diarrhoea and weight loss. — Due to decrease in the number of helper T-lymphocytes, the person gets easily infected by bacteria like Mycobacterium, viruses, fungi and even parasites like Toxoplasma. — The person is unable to protect himself/herself against any infection. • Diagnostic test for AIDS. HIV infection is diagnosed by ELISA (enzyme linked immunosorbent assay) test. • Treatment of AIDS — The treatment of AIDS with anti-retroviral drugs is only partially effective. — They can only prolong the life of the patient but cannot prevent death. • Prevention of AIDS — National AIDS Control Organisation (NACO) and other Non-Governmental Organisations (NGOs) are doing a lot to educate people about AIDS. — World Health Organisation (WHO) has started a number of programmes to prevent the spreading of HIV infection, that include: (i) Making blood (from blood banks) safe from HIV (ii) Ensuring the use of only disposable needles and syringes (iii) Free distribution of condoms (iv) Controlling drug abuse (v) Advocating safe sex (vi) Promoting regular check-ups for HIV in susceptible populations. Cancer • Cancer is defined as an uncontrolled proliferation of cells, which invade and damage the surrounding normal tissues. • Normal cells show a property called contact inhibition, by virtue of which contact with other cells inhibit their uncontrolled growth.

12 Biology-XII • Cancer cells lost the property of contact inhibition and continue to divide giving rise to masses of cells called tumors. • Type of Tumors. Tumors are of two types: (i) benign tumors and (ii) malignant tumors. • Causes of Cancer — Cancer may be induced by physical, chemical or biological agents. — These agents are called carcinogens. (i) P hysical agents. These agents include ionising radiations like X-rays and gamma rays and non-ionising radiation like UV rays causing DNA damage that leads to neoplastic transformation. (ii) Chemical agents. Chemical carcinogens like tobacco smoke is the major cause of lung cancer. (iii) B iological agents. These are the cancer causing viruses called oncogenic viruses have gene called viral oncogenic that induce cancer. — Cellular oncogenes (C-onc) or proto oncogenes present in normal cells, when activated under certain conditions, lead to oncogenic transformation of the cells. • Cancer Detection and Diagnosis Cancer detection is based on biopsy and histopathological studies of the tissue and blood, and bone marrow test for increased cell counts in the case of leukemias. (i) Biopsy and histopathology. In biopsy, a piece of the suspected tissue cut into thin sections is stained and examined under the microscope (histopathological studies) by a pathologist. (ii) Imaging. Techniques like radiography (use of X-rays), CT (computed tomography) and MRI (magnetic resonance imaging) are used to detect cancer of the internal organs. — CT uses X-rays to generate a three dimensional image of the internal organs. — MRI uses strog magnetic fields and non ionising radiations to detect pathological and physiological changes in the tissues. (iii) U se of antibodies. Antibodies against cancer specific antigens are also used for detection of certain cancers. (iv) M olecular biology. Techniques of molecular biology is also used to detect genes with inherited susceptibility to certain cancers. • Treatment of Cancer The common approach for treatment of cancer are surgery, radiation therapy, chemotherapy and immunotherapy. (i) Surgery. The cancerous tissue is removed surgically to reduce the load of cells. (ii) R adiation therapy. The tumor cells are irradiated lethally taking care of the surrounding tissue. (iii) C hemotherapy. Chemotherapeutic drugs are used to kill cancerous cells. However, majority of drugs have side effects like hair loss, anaemia etc.

Human Health and Diseases 13 (iv) Immunotherapy. It involves the use of biological response modifiers like α interferon, which activate the immune system and help in destroying the tumor. Most cancers are treated by combination of surgery, radiotherapy and chemotherapy. Drug and Alcohol Abuse • When the drugs are taken for a purpose other than medicinal use or in amounts/ frequency that impairs one’s physical, physiological or psychological functions, it constitutes drug abuse. • The drugs, which are commonly abused are opioids, cannabinoids and coca alkaloids. 1. Opioids — Opioids are the drugs obtained/prepared from the latex of poppy plant Papaver somniferum. e.g., morphine and heroin. 2. Cannabinoids — Natural cannabinoids are obtained from the inflorescences of the plant Cannabis sativa. — The flower tops, leaves and the resin of cannabis plant are used in various combinations to produce marijuana, hashish, charas and ganja. — Cannabinoids interact with cannabinoid receptors present principally in the brain. — They are generally taken by inhalation and oral ingestion. — They effect on cardiovascular system of the body. — These days cannabinoids are also being abused by some sports persons. 3. Coca Alkaloid or Cocaine — It is obtained from Coca plant (Erythroxylum coca) native to South America. — It is commonly called coke or crack and is usually snorted. — It interferes with the transport of the neuro-transmitter dopamine. — It has a potent stimulating action on Central Nervous System (CNS), producing a sense of euphoria and increased energy. — Excessive dosage of cocaine causes hallucinations, (i.e., a change in person’s thoughts feelings and perceptions.) 4. Some Other Hallucinogens — A tropa belladona and Datura are some other well known plants with hallucinogenic properties. 5. Some Other Similar Drugs — Drugs like barbiturates, amphetamines, benzodiazepines, lysergic acid diethyl- amide (LSD), normally used as medicines to help patients cope with mental illness like depression and insomnia are often abused. • Tobacco — Tobacco is smoked, chewed or used as a snuff. — It contains a large number of chemical substances including an alkaloid, nicotine.

14 Biology-XII — Nicotene stimulates adrenal gland to release adrenaline and non adrenaline, which raise blood pressure and increase heart rate. — Smoking is associated with increased incidence of cancers of lung, urinary bladder and throat, bronchitis, emphysema, coronary heart disease, gastric ulcer, etc. — Tobacco chewing is associated with increased risk of cancer of oral cavity. — Smoking increases carbon monoxide (CO) content in blood and reduces concentration of haem-bound oxygen, thus causing oxygen deficiency in the body. • Adolescence and Drug/Alcohol Abuse — Adolescence is ‘a period’ and ‘a process’ during which a child becomes mature in terms of his/her attitudes and beliefs for effective participation in society. — The period between 12–18 years of age may be considered as adolescence period. — Adolescence is a bridge linking childhood and adulthood and is accompanied by several biological and behavioural changes. — It is very vulnerable phase of mental and psychological development of an individual. • Causes of Drug/Alcohol Abuse Curiosity, need for adventure and excitement, and experimentation are the common causes among youngsters towards drug and alcohol abuse. — The first use of drugs or alcohol may be out of curiosity or experimentation but the later the child starts using these to escape facing problems. — Stress and pressures to excel in academics or examinations also play a significant role for youngsters to try alcohol and drugs. — The perception among youth that it is cool or progressive to smoke, use drugs or alcohol is also a major cause to start these habits. — Television, movies, newspapers, internet also help to promote this perception. — Unstable and unsupportive family structures and peer pressure have also been seen to be associated with drug and alcohol abuse. • Addiction and Dependence (i) Addiction. Psychological attachment to certain effects such as euphoria and a temporary feeling of well being, associated with drugs and alcohol is called addiction. — With repeated use of drugs, the tolerance level of the receptors present in the body increases. — Consequently, the receptors respond only to higher doses of drugs or alcohol leading to greater intake and addiction. — The use of these drugs even once, can be a fore-runner to addiction. (ii) D ependence. The tendency of the body to manifest a characteristic and unpleasant withdrawal syndrome, if regular dose of drug/alcohol is abruptly discontinued is called dependence. — It is characterised by anxiety, shakiness, nausea and sweating, which may be relieved when use is resumed again. — In some cases, withdrawal symptoms can be severe and even life threatening.

Human Health and Diseases 15 • Effects of Drug/Alcohol Abuse — The immediate effects of drugs and alcohol abuse are manifested in the form of reckless behaviour, vandalism and violence. — Excessive doses of drugs may lead to coma and death due to respiratory failure, heart failure or cerebral hemorrhage. — A combination of drugs or their intake along with alcohol may result in overdosing and even death. — When the drug is taken intravenously, it can lead to infections like AIDS and hepatitis. — Use of alcohol during adolescence can lead to heavy drinking in adulthood. — Chronic use of drugs and alcohol damages nervous system and liver (liver cirrhosis). — The use of drugs and alcohol during pregnancy adversely affect the foetus. • Common Warning Signs of Drug/Alcohol Abuse (i) Drop in academic performance, unexplained absence from school/college. (ii) Lack of interest in personal hygiene. (iii) Withdrawal and isolation from family and friends. (iv) Depression, fatigue, aggressive and rebellious behaviour. (v) Loss of interest in hobbies. (vi) Change in sleeping and eating habits. (vii) Fluctuations in weight and appetite. • Misuse of Drugs by Sports Persons — Some sports persons misuse certain drugs to enhance their performance. — They misuse narcotic analgesics, anabolic steroids, diuretics and certain hormones to increase muscle strength and bulk, promote aggressiveness and athletic performance. (a) Effects of anabolic steroids in Females (i) masculinisation (features like males). (ii) increased aggressiveness. (iii) mood swings and depression. (iv) abnormal menstrual cycles. (v) excessive hair growth on the face and body and facial acne. (vi) enlargement of clitoris. (vii) deepening of voice. (b) Effects of anabolic steroids in Males (i) Facial and body acne. (ii) increased aggressiveness. (iii) mood swings and depression. (iv) reduction of size of the testicles and decreased sperm production. (v) breast enlargement. (vi) potential for kidney and liver dysfunction.

26 Biology-XII 32. Bring out the differences between B-lymphocytes and T-lymphocytes. Ans. B-lymphocytes T-lymphocytes (i) These lymphocytes undergo (i) These lymphocytes mature in maturation in the bone marrow. thymus gland. (ii) They produce antibodies against (ii) They either directly attach the antigens. the antigens or stimulate the B-cells to produce antibodies. (iii) They do not respond to organ transplants. (iii) They react to organ transplants. 33. How do secondary lymphoid organs help in providing immunity? Ans.     —    S pleen contain lymphocytes and phagocytes and acts as a filter of the blood by trapping blood borne microorganisms. — Lymph nodes serve to trap the microorganisms or their 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. 34. How do the techniques of molecular biology helpful in preventing cancer? Ans.     —    T he techniques of molecular biology can be applied to detect genes in individuals with inherited susceptibility to certain cancers. — Identification of such genes, which predispose an individual to certain cancers, may be helpful in prevention of cancers. — Such individuals may be advised to avoid exposure to particular carcinogens to which they are susceptible (e.g., tobacco in case of lung cancer). 35. Enumerate the side effects of the use of anabolic steroids in females. Ans.    (i)    masculinisation (features like males) (ii) increased aggressiveness (iii) mood swings and depression (iv) abnormal menstrual cycles (v) exsessive hair growth on the face and body (vi) enlargement of clitoris (vii) deepening of voice and (viii) acne and premature closure of growth centres of the long bones may result in stunted growth. 36. List the side effects of the use of anabolic steroids in males. Ans.    (i)     increase aggressiveness (ii) mood swings and depression (iii) reduction of size of the testicles (iv) decreased sperm production (v) potential for kidney and liver dysfunction

Human Health and Diseases 27 (vi) breast enlargement. (vii) premature baldness (viii) enlargement of the prostate gland. (ix) acne and premature closure of growth centres of long bones may result in stunted growth. 37. What is a carcinogen? Name one chemical carcinogen with its target tissue. Ans. The physical, chemical or biological agents that transform the normal cells into cancerous neoplastic cells are called carcinogens. — Tobacco smoke is a carcinogen that causes lung cancer. 38. How do B-cells of the immune system respond to antigens? Ans. B-cells produce an army of proteins in response to an antigen (pathogen) into our blood. — These proteins are called antibodies, which help to fight the pathogen. 39. What harm do cancerous cell cause? Ans.    —    T  he cancer cells grow very rapidly, invading and damaging the surrounding normal tissues. — These cells actively divide and starve the normal cells by competing for vital nutrients. 40. What is contact inhibition? How does this phenomenon operate in cancer cells? Ans. Contact inhibition is the property of normal cells by virtue of which contact with other cells inhibits their uncontrolled growth. — In cancer cells there is breakdown of this regulatory mechanism that prevents the uncontrolled growth. 41. What are allergens? How do they cause inflammatory response inside the human body? Ans.     —    T he substances that produce exaggerated response of the immune systems are called allergens. — They bind with mast cells, which release chemicals like histamine and serotonin to cause inflammatory response. 42. Enumerate any two properties of cancer cells that distinguish them from normal cells. Ans.     —    C ancer cells continue to divide to give rise masses of cells called tumors. — They exhibit the phenomenon called metastasis, i.e., the cells sloughed from tumors reach distant sites through blood and produce new tumors there. 43. Write the full form of ELISA. Give an example of the clinical application of ELISA test. Ans.     —    E LISA—Enzyme Linked Immunosorbent Assay. — It is used as diagnostic test for AIDS.

28 Biology-XII 44. Name and explain the type of barrier of innate immunity system, which involves macrophages. Ans.     —    C ellular barriers. — Certain types of leukocytes (WBC) of our body like polymorphonuclear leucocytes (PMNL–neutrophils) and monocytes and natural killer (type of lymphocytes) in the blood as well as macrophages in tissues can phagocytose and destroy microbes. 45. Name and explain the type of barrier of innate immunity, where some cells release interferons when infected. Ans.     —    Cytokine barriers. — Virus infected cells secrete proteins called interferons, which protect non- infected cells from further viral infection. 46. Why is using tobacco in any form injurious to the health? Explain. Ans.     —    T obacco contains nicotene, which stimulates adrenal gland to release adrenaline and nor-adrenaline, which increase blood pressure and heart beat. — Smoking is associated with increased incidence of cancers of lung, urinary bladder and throat, bronchitis, emphysema, coronary, heart disease, ulcers etc. — Tobacco chewing is associated with increased risk of cancer of oral cavity. — Smoking increases carbon monoxide (CO) content in blood and reduce the concentration of haem bound oxygen. 47. Due to undue peer pressure a group of adolescents started using opioids intravenously. What are the serious problems they might face in future? Ans.     —    S uch adolescents are likely to acquire serious infections like AIDS and Hepatitis B. The viruses, which are responsible for these diseases, are transferred from one person to another by sharing of infected needles and syringes. — Both AIDS and Hepatitis B infections are chronic infections and ultimately fatal. — As the tolerance of the receptors to these drugs increases the adolescents develop dependence to these drugs. 48. Name the blank spaces a, b, c and d in the table given below. Name of the Drug Plank Source Organ System Affected (i) a Poppy plant b (ii) Marijuana d c Ans.     (i)   a – Morphine   b – Central Nervous system (ii) c – Cannabis sativa.  d – Cardiovascular system.

Human Health and Diseases 29 49. How do normal cells get transformed into cancerous neoplastic cells? Mention the difference between viral oncogenes and cellular oncogenes. Ans.    —    T  ransformation of normal cells into cancerous neoplastic cells is induced by physical, chemical or biological agents, collectively called as carcinogens. Viral Oncogenes Cellular Oncogenes The genes of viruses that cause Certain genes present in normal cells, when cancer are called viral oncogenes. activated lead to oncogenic transformation of cells, are called cellular oncogens. 50. List the specific symptoms of amoebiasis. Name the causative organism. Ans.     —    The symptoms of amoebiasis include: (i) constipation (ii) abdominal pain and cramp (iii) stools with excess mucus and blood clots. — It is caused by Entamoeba histolytica. 51. (i) What does the above diagram illustrate? (ii) Name the parts labelled ‘a’ and ‘b’ (iii) Name the type of cells that produce this molecule. Ans.    (i) The diagram illustrate the structure of an antibody molecule. (ii) a–antigen binding site b–Heavy chain (iii) B. lymphocytes (B-cells).

30 Biology-XII 52. (a) N ame the lymphoid organ in humans where all the blood cells are produced. (b) Where do the lymphocytes produced by the lymphoid organ mentioned above migrate and how do they affect immunity? Ans.    (a)  Bone marrow. (b) — Some of the lymphocytes move to thymus for maturation into T-lymphocytes — They are involved in cell mediated immunity. 53. List the specific symptoms of typhoid. Name its causative agent. Ans. The symptoms of typhoid include. (i) Sustained high fever (39° to 40°C) (ii) Weakness and headache (iii) Stomach pain and constipation (iv) Loss of appetite. Typhoid is caused by a bacteria, Salmonella typhi 54. Name the type of cells the AIDS virus first enters into, after getting inside the human body. Explain the sequence of events that the virus undergoes within these cells to increase their progeny. Ans.     —   A  IDS virus first enters the macrophage cells after getting inside the human body. — The RNA genome of the virus undergoes reverse transcription to form DNA with the help of enzyme reverse transcriptase. — The viral DNA become incorporated into the DNA of host cells and directs the host cells to produce new viral particles. 55. (a) Explain the property that prevents normal cells from becoming cancerous. (b) A ll normal cells have inherent characteristic of becoming cancerous, Explain. Ans.   (a)     Contact inhibition is the property shown by normal cells by the virtue of which contact with other cells inhibits their uncontrolled proliferation and growth. (b) All normal cells have cellular oncogenes (c-onc) or proto-oncogenes; when activated under certain conditions, such genes could lead to oncogenic transformation of normal cells, (i.e., they become cancerous). 56. List the specific symptoms of pneumonia. Name the causative organism. Ans. The specific symptoms include; (i) Fever, chill and headache (ii) In sever cases the lips and finger nails may turn gray to bluish in colour.    It is caused by Streptococcus pneumoniae and Haemophilous influenzae.

Chapter-2 Microbes in Human Welfare (NCERT Textbook Chapter-10) Important Notes/Chapter at a Glance • Microbes are present everywhere—in soil, water, air, inside our bodies and that of other animals and plants. They are also present, at the sites, where no other life form could possibly exist such as inside thermal geysers (thermal vents) where temperature may be as high as 100°C deep in the soil, under the snow and highly acidic environments. • Microbes are diverse such as protozoa, bacteria, fungi, viruses, viroids and prions (proteinaceous infectious agents). • Microbes like bacteria and fungi can be grown on nutritive media to form colonies. Such cultures are useful in studies on microorganisms. • Microbes cause large number of diseases in plants and animals including man. However, several microbes are useful to man in diverse ways. MICROBES IN HOUSEHOLD PRODUCTS 1. Curd. Microorganisms such as Lactobacillus and others commonly called Lactic Acid Bacteria (LAB) grow in milk and convert it into curd. • During growth LAB produce acids that coagulate and partially digest the milk protein. • For the preparation of curd a small amount of curd that contain millions of LAB, is added to the fresh milk as inoculum or starter that convert milk to curd. Why is curd more nutritious than milk? (i) LAB partially digest the milk proteins. (ii) LAB also increase the nutritional quality of curd by increasing vitamin-B12. (iii) In our stomach LAB play beneficial role in checking disease causing microbes. 2. Idli and Dosa. The dough used for making foods such as idli and dosa is fermented by bacteria; the puffed up appearance is due to the CO2 produced during fermentation. 3. Bread. The dough used for making bread is fermented using baker’s yeast (Saccharomyces cerevisiae). 4. Toddy. Toddy, a traditional drink of some parts of Southern India is produced by fermenting sap from palms. 5. Other Fermented Foods. Microbes are also used to ferment fish, soyabean and bamboo shoots to make foods. 6. Cheese. Cheese is one of the oldest food items in which microbes were used; the specificity of different varieties of cheese, known by their characteristic texture, flavour and taste comes by the microbes used. For example:

Microbes in Human Welfare 47 (i) Swiss cheese has large holes, due to the production of large amount of carbon dioxide by the bacterium, Propionibacterium sharmanii. (ii) Roquefort cheese are ripened by growing a specific fungi on them. MICROBES IN INDUSTRIAL PRODUCTS • In industries, microbes are used to produce: (i) beverages (ii) antibiotics (iii) organic acids (iv) enzymes (v) bioactive molecules, etc. For production of these substances on an industrial scale, microbes are grown in very large vessels called fermentors. 1. Fermented Beverages — Yeast (Saccharomyces cerevisiae) commonly called brewer’s yeast is used for making beverages like wine, beer, whisky, brandy or rum. — The materials like malted cereals and fruit juices are used to produce ethanol by fermentation. — Depending upon the type of raw material used and the nature of processing, various types of alcoholic drinks are produced, e.g., (i) wine and beer—are produced without distillation of the fermented broth. (ii) whisky, brandy and rum—are produced by distillation of the fermented broth. 2. Antibiotics — The term antibiotics derived from the Greek words anti-against and bios-life, means against life (with reference to disease causing organisms); whereas with reference to human beings, they are ‘pro life’ and not against as they save human lives from several infections/pathogenic. — Antibiotics are chemical substances, which are produced by some microbes and can kill or retard the growth of other (disease causing) microbes. — Penicillin was the first antibiotic, discovered by Alexander Fleming, while working on Staphylococci, which could not grow due to the chemical produced by the mould Penicillium notatum. — Its full potential as an effective antibiotic was established by Ernest Chain and Howard Florey, who were awarded the Nobel Prize in 1945. — This antibiotic was extensively used to treat American soldiers wounded in world war II. — Antibiotics are used to treat a number of diseases like diphtheria (gal ghotu), leprosy (kusht rog), plague, whooping cough (Kali Khansi) etc. 3. Chemicals, Enzymes and other Bioactive Molecules Microbes are also used for commercial and industrial production of certain chemicals like organic acids, enzymes, alcohols etc.

48 Biology-XII (i) Organic acids Some Organic Acids produced on commercial/industrial scales and the Microbe employed in their production are listed in the given table. Organic Acid Microbe Used (i) Citric acid Aspergillus niger (fungus) (ii) Acetic acid Acetobacter aceti (bacterium) (iii) Butyric acid Clostridium butylicum (bacterium) (iv) Lactic acid Lactobacillus (bacterium) (ii) Ethanol Yeast (Saccharomyces cerevisiae) is used for commercial production of ethanol. (iii) Enzymes Microbes are also used for the production of enzymes: — The enzymes produced from microbes include lipases, pectinases, proteases and streptokinase. — Lipases are used in detergent formulation and are helpful in removing oily stains from the laundry. — Pectinases and proteases are used to clear bottled fruit juices. — Streptokinase produced from Streptococcus and modified by genetic engineering is used as a ‘clot buster’ for removing the blood clots from the blood vessels of patients who have undergone myocardial infraction leading to heart attack. (iv) Bioactive molecules Bioactive molecules are drugs/medicines other than antibiotics which are obtained from certain microbes and are used to treat certain human ailments: e.g., — C yclosporin-A produced by the fungus Trichoderma polysporum is used as an immunosuppressive agent in organ transplant patients. — Statins produced by a type of yeast, Monascus purpureus is used as blood cholesterol lowering agent; it acts by competitively inhibiting the enzyme responsible for synthesis of cholesterol. MICROBES IN SEWAGE TREATMENT A large quantity of waste water called sewage is generated everyday in cities and towns. The major component of this waste water is human excreta: • The municipal waste-water sewage contains large amounts of organic matter and microbes, many of which are pathogenic. • The sewage is treated in Sewage Treatment Plants (STPs) before it is discharged into water bodies to reduce the pollution. • This treatment is carried out in two stages: (i) Primary treatment and (ii) Secondary treatment.

Microbes in Human Welfare 49 (i) Primary Treatment — It involves physical removal of large and small particles from sewage through filteration and sedimentation. — Initially, floating debris is removed by sequential filteration. — Then the grit (soil and small pebbles) are removed by sedimentation. — All solids that settle form the primary sludge, and the supernatant forms the effluent. — Then, the effluent from the primary settling tank is taken for secondary treatment. (ii) Secondary Treatment or Biological Treatment — The primary effluent is passed into aeration tank, where it is constantly agitated and air is pumped into it. — This allows rapid growth of aerobic microbes into ‘flocs’ (masses of bacteria associated with fungal filaments), which consume the organic matter of the sewage and reduce BOD (biochemical oxygen demand). — When the BOD of sewage is reduced significantly, the effluent is passed into settling tank, where the bacterial flocs are allowed to sediment forming the activated sludge. — A small part of the activated sludge is pumped back into the aeration tank as inoculum. — The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digester, where the anaerobic bacteria digests, the bacterial flocs and fungi present in the sludge producing methane, hydrogen sulphide and carbon dioxide. — These gases form biogas, which is used as a source of energy. — The effluent from the secondary treatment plant is generally released into water bodies like streams or rivers. RIVER ACTION PLANS • Due to increasing urbanisation sewage is being produced in much larger quantities. • However, the number of STPs has not increased enough, so the intreated sewage is often discharged directly into rivers, leading to pollution and increasing incidence of water borne diseases. • The Ministry of Environment and forests has initiated programmes like Ganga Action Plan and Yamuna Action Plan to save the major rivers of our country from pollution. • Under these plans a large number of STPs are to be build, so that only treated sewage may be discharged in the rivers. MICROBES IN PRODUCTION OF BIOGAS • Biogas is a mixture of gases (containing predominantly methane) produced by microbial activity which may be used as fuel. • Methanogens like Methanobacterium produce large quantities of methane, along with carbon dioxide and hydrogen, by acting on cellulosic materials.

50 Biology-XII • These bacteria are commonly found in the anaerobic sludge during sewage treatment, and also in the rumen (a part of stomach) of cattle. • A lot of cellulosic material is present in the food of cattle; in the rumen these bacteria help in break down of cellulose. • The excreta (dung) of cattle, commonly called gobar rich in methanogens, is used for generation of biogas, commonly called gobar gas. • The technology of biogas production was developed in India by Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC). MICROBES AS BIOCONTROL AGENTS • Biocontrol refers to the use of biological methods for controlling plant diseases and pests; these methods rely on natural predation rather than introduced chemicals. • The use of insecticides and pesticides are not only extremely harmful to human beings and animals but also polluting our environment. • Biological Control of Pests and Diseases — The organic farming is thought to be more sustainable and improve the biodiversity health. — The organic farmer works to create a system, where the pests are not eradicated, but are kept at manageable levels by a complex system of check’s and balances within the ecosystem. — Further, the eradication of the creatures i.e., pests is undesirable because without them the beneficial insects which feeds on them would not be able to survive. — Thus, the use of biocontrol measures will greatly reduce our dependence on toxic chemicals and pesticides. Some Examples of Biological Control of Pests and Diseases: (i) The Lady bird (a beetle with red and black markings) and Dragon flies are useful to control aphids and mosquitoes respectively. (ii) The bacteria, Bacillus thuringiensis (often written as Bt). Whose spores are mixed with water and sprayed on crops like brassicas and fruit trees; which, when eaten by the insects larvae, the toxin of the spores released in the gut, kills the larvae, and leaves other insects unharmed. (iii) By using the technique of genetic engineering, scientists have introduced B. thuringiensis toxin genes into crop plants, which have become resistant to insect pests, e.g., Bt cotton. (iv) Trichoderma species (free living fungi) are effective biological control agents of several plant pathogens. (v) Baculoviruses (viruses that attack insects and other arthropods) belonging to genus Nucleopolyhedrovirus can be used as species-specific narrow spectrum insecticides. They do not have negative impacts on plant, mammals, birds, fish or even non- target insects. MICROBES AS BIOFERTILISERS • The use of chemical fertilizers to increase agricultural produce has contributed significantly to environmental pollution.

Microbes in Human Welfare 51 • Therefore, there is a need to switch over to organic farming i.e., the use of biofertilizers to enhance the agricultural output. • Biofertilisers are organisms that enrich the nutrient quality of the soil. • The main source of biofertilizers are bacteria, fungi and cyanobacteria. (i) Bacteria — R hizobium occurs in symbiotic association with the roots of leguminous plants, these bacteria fix atmospheric nitrogen into organic form, which is used by the plant as nutrient. — Azospirillum and Azotobacter are free living bacteria, that can also fix atmospheric nitrogen, thus enriching the nitrogen content of the soil. (ii) Fungi — Some fungi also form symbiotic associations with roots of higher plants (called mycorrhiza), e.g., members of genus Glomus. — The fungi absorbs phosphorus from the soil and passes it to the plant. — The mycorrhizae also provide other benefits like (i) resistance to root borne pathogens (ii) tolerance to salinity and drought, and (iii) over all increase in plant growth and development. (iii) Cyanobacteria — Cyanobacteria (blue green algae) are autotrophic microbes distributed in aquatic and terrestrial environment, which fix atmospheric nitrogen, e.g., Anabaena, Oscillatoria, Nostoc etc. — In paddy fields, cyanobacteria serve as important biofertilisers. — Cyanobacteria (blue green algae) also add organic matter to the soil and increase its fertility. — Presently, a number of biofertilizers are available commercially in the market and farmers can use these to replenish soil nutrients and to reduce the dependence on chemical fertilizers. Very Short Answer Type Questions 1. Name the type of association the genus Glomus exhibits with higher plants. Ans. Symbiotic association. 2. Give the binomials of two types of yeast and the commercial bioactive products they help to produce. Ans.    (i)     Saccharomyces cerevisiae – Alcoholic beverages and bread. (ii) Monascus purpureus – Cyclosporin A. 3. Bacteria cannot be seen with the naked eyes, but these can be seen with the help of microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes under a microscope, which sample would you carry and why? Ans. Curd; Curd contains millions of Lactic Acid Bacteria (LAB).

52 Biology-XII 4. Name any two species of fungus, which are used in the production of antibiotics. Ans. Penicillium notatum and P. chrysogenum; both yield penicillin. 5. Name the diverse type of microbes. Ans. Protozoa, bacteria, fungi, viruses, viroids and prions. 6. What are LAB? Ans. Microorganisms such as Lactobacillus and others which grow in milk and convert it into curd are called LAB (lactic acid bacteria). 7. How does a small amount of curd added to the fresh milk, convert it into curd? Ans. The curd contains millions of Lactic Acid Bacteria (LAB), which multiply and produce acids that converts milk into curd. 8. What beneficial role do LAB play in our stomach/intestine? Ans. In our stomach LAB help in checking disease causing microbes. 9. What is the puffed up appearance of dough used for making dosa and idli due to? Ans. The puffed up appearance is due to the production of CO2 by bacterial fermentation. 10. Why does ‘Swiss Cheese’ have large holes in it? Ans. The large holes in ‘Swiss Cheese’ are formed due to production of a large amount of CO2 by a bacterium named Propionibacterium sharmanii. 11. What does the term ‘antibiotics’ mean? Why is it a misnomner? Ans. Anti is a Greek word that means ‘against’, and bio means ‘life’, together they mean ‘against life’ (in the context of disease causing organisms), where as with reference to human beings, they are ‘pro life’ and not against. 12. Who discovered the first antibiotics? Give the scientific name of mould from which, it was discovered. Ans. Alexander Fleming; Penicillium notatum. 13. Name the scientist who won Nobel Prize for the discovery of Penicillin. Ans. Alexander Fleming, Ernest Chain and Howard Florey. 14. What makes detergents capable of removing oily stains from the laundry? Ans. The enzyme lipase make detergents capable of removing oily stains from laundry. 15. Why are bottled fruit juices appear clearer than the home made ones? Ans. It is because the bottled fruit juices are clearified by the use of enzymes pectinases and proteases. 16. What is the medical use of cyclosporin-A? Ans. Cyclosporin-A is used as an immuno-suppressive agent in organ-transplant patients. 17. How do statins reduce the blood cholesterol level? Ans. Statins reduce blood cholesterol level by competitively inhibiting the enzyme responsible for synthesis of cholesterol.

Microbes in Human Welfare 53 18. What are the basic processes involved in primary treatment of sewage treatment plant? Ans. It involves physical removal of particles through filteration and sedimentation. 19. What is the significance of BOD in sewage treatment? Ans. BOD (Biochemical oxygen demand) test measures the rate of uptake of oxygen by microorganisms in a sample of water and thus, indirectly BOD is the measure of organic matter present in the sewage water. 20. What function do methanogens perform in the rumen of cattle? Ans. Methanogens help in the breakdown of cellulose and play important role in the nutrition of cattle. 21. Which of the following is a cyanobacteria that can fix atmospheric nitrogen? Azospirillum, Oscillatoria, Spirulina. Ans. Oscillatoria. Short Answer Type Questions (Type-I) 1. How does addition of a small amount of curd to fresh milk help formation of curd? Mention a nutritional quality that gets added to the curd. Ans.     —  T he small amount of curd added to the milk contains millions of Lactic Acid Bacteria (LAB), which at suitable temperature multiply, thus converting milk to curd. — LAB produce acids that coagulate and partially digest the milk proteins. — LAB also increase vitamin B12 and thus improves nutritional quality of curd. 2. How do plants benefit from having mycorrhizal association? Ans.    —    T he fungal symbiont absorbs phosphorus from the soil and passes it to the plant. — It provides resistance to root borne pathogens, tolerance to salinity and drought. — It also show overall increase in plant growth and development. 3. Name the bacterium responsible for the large holes seen in “Swiss Cheese”. What are these holes due to? Ans. Propionibacterium sharmanii — The large holes in the cheese are due to the production of large amount of CO2 by the bacterium. 4. Explain the significant role of the genus Nucleopolyhedrovirus in an ecological sensitive area. Ans.     —   N ucleopolyhedrovirus can be used as species specific narrow spectrum insecticidal application. — These viruses have no negative impacts on plants, mammals, birds, fish or even on non-target insects.

54 Biology-XII Therefore, these are desirable when beneficial insects are to be conserved to help in an overall integrated pest management (IPM) programme or in an ecologically sensitive area. 5. Mention a product of human welfare obtained with the help of each one of the following microbes. (a) LAB (b) Saccharomyces cerevisiae (c) Propionibacterium sharmanii (d) Aspergillus niger Ans.   (a)    Curd (b) Bread and Alcoholic beverage (Ethanol) (c) Swiss cheese (d) Citric acid. 6. Explain the different steps involved during primary treatment phase of sewage. Ans.     —    I t involves physical removal of large and small particles through filteration and sedimentation. — Initially floating debris is removed by sequential filteration. — Then the grit (soil and small pebbles) are removed by sedimentation. — All solids that settle from the primary sludge and the supernatant forms the effluent, which is taken for secondary treatment. 7. Explain the function of ‘anaerobic sludge digester’ in a sewage treatment plant. Ans. The major part of the activated sludge produced during the secondary treatment is pumped into large tanks called anaerobic sludge digester, where the anaerobic bacteria digests, the bacterial flocs and fungi present in the sludge. It produces methane, hydrogen sulphide and carbon dioxide. — These gases constitute biogas, which is used as fuel. 8. List the events that reduce the Biochemical Oxygen Demand (BOD) of a primary effluent during sewage treatment. Ans. The primary effluent is passed into large acration tanks, where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful acrobic microbes into flocs. While growing these microbes consume the major part of the organic matter in the effluent. 9. Name a genus of baculovirus. Why are they considered good biocontrol agents? Ans. Nucleopolyhedrovirus: They are excellent candidates for species – specific, narrow spectrum insecticidal applications. They show no negative impacts on plants, mammals, birds, fish or even non-target insects.

Microbes in Human Welfare 55 10. Name the microbes that help production of the following products commercially. (a) Statin (b) Citric acid (c) Penicillin (d) Butyric acid Ans.   (a)    Monascus purpureus (b) Aspergillus niger (c) Penicillium notatum (d) Clostridium butylicum 11. Write the binomial of two fungi and mention the products/bioactive molecules they help to produce. Ans. Aspergillus niger – Citric acid Trichoderma polysporum – Cyclosporin A. 12. In which food would you find lactic acid bacteria? Mention some of their useful applications. Ans.     —      Lactic Acid Bacteria (LAB) are present in curd. — Some useful applications are: (i) LAB present in the inoculum/starter (small quantity of milk added to the milk) help in converting milk into curd. (ii) In our stomach LAB help in checking disease causing pathogens. 13. Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes. Ans.    (i)     Wheat—bread (ii) Rice—idli and dosa (iii) Bengal gram—dhokla 14. What is sewage? In which way can sewage be harmful to us? Ans.     —    The municipal waste water is called sewage. — Sewage contains many microbes that are pathogenic. — It pollutes water bodies, if discharged into them. 15. Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20 mg/L, 8 mg/L and 400 mg/L, respectively, which sample of the water is most polluted? can you assign the correct label to each assuming the river water is relatively clean? Ans.      —   Sample C—is the most polluted water; — Sample A—River water, Sample B—secondary effluent, Sample C—untreated sewage. 16. Find out the name of the microbes from which cyclosporin A (an immunosuppressive drug) and statins (blood cholesterol lowering agents) are obtained.

66 Biology-XII Ans.    (i)    Lactic Acid Bacteria (LAB) are used to make curd. Baking yeast (Saccharomyces cerevisial) is used for making bread. Dough, which is used for making foods such as dosa and idli is fermented by bacteria. (ii) Methanobacterium (a methanogen/methane producing bacteria) (iii) These bacteria are naturally present in the excreta (dung) of cattles. 12. Nitin and his friend Sumit visited a village, where they show some farmers spraying insecticides and pesticides on their crops. (i) They argued with the farmers that spraying of such chemicals is harmful. Why did they say so? Give atleast two reasons. (ii) Suggest an alternative method of controlling the pest and explain, how is this method better than the chemical method of pest control? (iii) Give any one example, where the alternative method had been used to get rid of a pest? Ans.     (i)    — These chemicals do not discriminate between harmful and useful insect, and also kill useful insects alongwith harmful pests. — They are toxic and extremely harmful, to animals and human beings and pollute the environment. (ii) Biological control of pest, which involves the use of other live organism that feeds on such pests. Such method neither harm the animals/humans nor pollute the environment. (iii) The Ladybird beetle is used to get rid of aphids. Case Study Based MCQs I. Biogas is a methane rich fuel gas, produced by anaerobic breakdown or digestion with the help of methanogenic bacteria. Biogas is composed of methane (50–70%), carbon dioxide (30–40%) with traces of hydrogen sulphide, hydrogen and nitrogen. You have learnt that microbes produce different types of gaseous end products during growth and metabolism. The type of the gas produced, depends upon the microbes and the organic substrates they utilize. Certain bacteria which grow anaerobically on cellulosic materials, produce large amount of methane along with CO2 and H2. These bacteria are collectively called methanogens. One such common bacterium is Methanobacterium. Methanogens are commonly found in the anaerobic sludge during sewage treatment. They are also present in the rumen part of the stomach of cattle, where they help in the breakdown of cellulose, and thus play an important role in the nutrition of cattle. Methanogens are also present in large numbers in the excreta (dung, also called ‘gobar’) of cattle. The cattle excreta is also rich in cellulosic wastes, hence can be used for generation of biogas commonly called ‘gobar gas’. 1. The microorganism used in the production of biogas is (a) Chlorella (b) Methanobacterium (c) Saccharomyces (d) Nostoc Ans. (c)

Microbes in Human Welfare 67 2. A sewage treatment process in which a part of decomposer bacteria present in the wastes is recycled into the starting of the process is called (a) Cyclic treatment (b) Activated sludge treatment (c) Primary treatment (d) Tertiary treatment. Ans. (b) 3. Select the correct statement from the following: (a) Biogas, commonly called gobar gas is pure methane (b) Activated sludge sediment in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria (c) Biogas is produced by the activity of aerobic bacteria on animal waste (d) Methanobacterium is an aerobic bacterium found in rumen of cattle. Ans. (b) 4. Biogas produced by fermentation of manure, sewage, cattle dung, etc. predominantly comprises (a) Methane, nitrogen and hydrogen (b) Methane and carbon dioxide (c) Methane and carbon monoxide (d) Methane and nitric oxide. Ans. (b) 5. The technology of biogas production from cow dung was developed in India largely due to the efforts of (a) Gas Authority of India (b) Oil and Natural Gas Commission (c) Indian Agricultural Research Institute and Khadi and Village Industries Commission (d) Indian Oil Corporation Ans. (c) II. During the cultivation, crops are threatened by number of pathogens and pests. Therefore, crops have to be protected by killing or removing pathogens and pests. This is carried through the use of chemical pesticides and insecticides. These chemicals are toxic and extremely harmful to human beings and animals alike. They not only pollute our environment (soil and ground water), but also make the fruits, vegetables and other crop plants poisonous. The weedicides used to remove the weeds from the fields pollute our soil. Therefore, instead eradicating pests and pathogens through chemicals, it is better to use biologicals agents for controlling them. The natural method of pest and pathogen control involving use of viruses, bacteria, fungi and other insects is called biocontrol or biological control. For example, Ladybird beetle (beetle with red and black markings) and Dragonflies are used to get rid of aphids and mosquitoes respectively. 1. An undistilled alcoholic beverage produced from grain mash fermentation is (a) Curd (b) Rum (c) Beer (d) Wine Ans. (c)

68 Biology-XII 2. Cyanobacteria helps farmers by (a) Reducing the alkalinity of soil (b) Reducing the acidity of the soil (c) Neutralising the alkalinity of soil (d) Water logging Ans. (b) 3. Cultivation of Bt cotton has been much in the news. The prefix ‘Bt’ means (a) Barium treated cotton seeds (b) ‘Bigger thread’ variety of cotton with better tensile strength (c) Produced by ‘biotechnology’ using restriction enzymes and ligases (d) Carrying an endotoxin gene from Bacillus thuringiensis. Ans. (d) 4. A common biocontrol agent for the control of plant diseases is (a) Glomus (b) Trichoderma (c) Baculovirus (d) Bacillus thuringiensis Ans. (c) 5. Which of the following can be used as a biocontrol agent in the treatment of plant disease? (a) Lactobacillus (b) Trichoderma (c) Chlorella (d) Anabaena Ans. (b)

Unit IX Biotechnology and its Applications 3. Biotechnology: Principles and Processes (NCERT Textbook Chapter-11) 4. Biotechnology and its Applications (NCERT Textbook Chapter-12)



Chapter-6 Biodiversity and its Conservation (NCERT Textbook Chapter-15) Important Notes/Chapter at a Glance • The term ‘Biodiversity’ was popularised by the sociobiologist Edward Wilson to describe ‘the combined diversity at all the levels of biological organisation’. • In our biosphere immense diversity (or heterogeneity) exists at all levels of biological organisation ranging from macromolecules within cells to biomes. • The most important levels of biodiversity are: Genetic diversity, species diversity and ecological diversity. • It has taken millions of years of evolution to develop this rich diversity in nature. • We could lose all that wealth is less than two centuries, if the present rates of species losses continue. • According to IUCN (2004), the total number of plant and animal species described so far is slightly more than 1.5 million. • But, we have no clear idea about the total number of species that exist on Earth. • A conservative and scientifically sound estimate has been made by Robert May, puts the global species diversity at about 7 million. • More than 70 per cent of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) account for about 22 per cent. • Among animals, more than 70 per cent are insects. Prokaryotic Species • Biologists are not sure about the number of prokaryotic species due to following reasons. (i) The conventional taxonomic methods are not suitable for identifying microbial species. (ii) Many of the prokaryotic species cannot be cultured in laboratory conditions. • If we accept biochemical or molecular criteria for deciding a species, their number might run into millions. Biodiversity in India • India has only 2.4 per cent of the world’s land area, but has 8.1 per cent global species biodiversity. • Hence, India is one of the 12 mega diversity countries of the world. • In India there are about 45000 species of plants and twice as many of animals; many more species are yet to be discovered and named. • If we apply Robert May’s global estimates, then only 22 per cent of the total species have been recorded so far. • There are probably more than 1,00,000 plant species and more than 3,00,000 animal species yet to be discovered and described.

Biodiversity and its Conservation 153 Patterns of Biodiversity • Biodiversity is not uniform throughout the world but varies with change in latitude and altitude. Latitudinal Gradients • In general, species diversity decreases as we move away from the equator towards the poles. • With very few exceptions, tropics (latitudal range of 23.5°N to 23.5°S) harbour more species than temperate or polar areas e.g. (i) Colombia located near the equator has nearly 14,000 species of birds while New York at 41°N has 105 species and Greenland at 71°N only 56 species. (ii) India, with much of its land area in the tropical latitudes, has more than 1,200 species of birds. (iii) A forest in a tropical region like Equator has up to 10 times as many species of vascular plants as a forest of equal area in a temperate region like the Midwest of the USA. (iv) The Amazonian rain forest in South America has the greatest biodiversity on earth; it harbours about 40,000 species of plants, 1,25,000 species of insects, 3,000 of fishes, 1,300 of birds, 427 of mammals, 427 of amphibians, 378 of reptiles and more than 1,25,000 of invertebrates. Hypotheses for Higher Biodiversity in the Tropical Areas Evolutionary biologists have proposed following hypotheses to explain higher biodiversity in the tropical regions: (i) Speciation is generally a function of time; The temperate regions have undergone frequent glaciations in the past, which killed most of the species. But species continued to flourish and evolve undisturbed for several years in the tropical regions as no such disturbances occurred there. (ii) As more solar energy is available in the tropics, which contributes to higher productivity and biodiversity in the tropics. (iii) Tropical environments are more constant and predictable, which promote niche specialisation and lead to a greater species diversity. Species Area Relationship • German naturalist and geographer Alexander Von Humboldt made pioneer and extensive exploration in the wilderness of South American jungles. • He observed that within a region species richness increased with increasing explored area, but only upto a limit. Importance of Species Diversity to Ecosystems • Ecologists believe that communities with more species tend to be more stable than those with less species. • A stable community has the following attributes: (i) It should not show too much variation in productivity from year to year. (ii) It must be either resistant or resilient to seasonal disturbances. (iii) It must also be resistant to invasions by alien species.

154 Biology-XII • David Tilman had shown the following features, through his ecological experiments using outdoor plots: (i) The plots with more species showed less year to year variation in total biomass. (ii) The plots with increased diversity showed higher productivity. • We now realise that rich biodiversity is not only essential for ecosystem health, but imparative for the survival of the human race on the Earth. Rivet Popper Hypothesis It was given by Stanford ecologist Paul Ehlrich, to explain the importance of species diver- sity to the ecosystem. — It states that if an aeroplane equivalent to an ecosystem has thousands of rivets equivalent to species. — If each passenger removes a rivet (= species) from the aeroplane, then it may not effect flight safety initially but over a period of time, it may make the plane dangerously weak. — Removal of rivets (= species) from a critical part (= species performing major ecosystem functions) like wing will pose an immediate and serious threat to safety of the flight. — This analogy is comparable to the functioning of an ecosystem. Loss of Biodiversity • The colonisation of tropical Pacific Islands by human beings has led to the extinction of more than two thousand species of native birds. • The IUCN Red List (2004) document the extinction of 784 species in the last 500 years that include 359 invertebrates, 338 vertebrates and 87 plants. • Some of the animals that have become extinct recently include: (i) Steller’s sea cow (Russia) (ii) Dodo (Mauritius) (iii) Thylacine (Australia) (iv) Quagga (Africa) (v) Three sub-species (Bali, Javan, Caspian) of Tiger. • 27 species have become extinct in the last twenty years. • More than 15,500 species worldwide are facing threat including 12 per cent of bird species, 23 per cent of all mammal species, 32 per cent of all amphibian species and 31 per cent gymnosperm species. The records show that extinctions across taxa are not random; some groups like amphibians appear to be more vulnerable to extinction. • Before humans appeared on Earth, there have been five episodes of ‘mass extinction’ (i.e., loss of large number of species in a short time), and ‘Sixth Extinction’ presently in process. • The current rate of species extinction is 100–1,000 times faster than the pre-human times and our activities are responsible for the faster rate.

Biodiversity and its Conservation 155 Consequences of Loss of Biodiversity • Loss of biodiversity in a region can lead to the following: (i) Decline in plant production (ii) Lowered resistance to environmental perturbation. (iii) Increased variability in ecosystem processes like water use, pest/disease cycles, plant productivity, etc. Causes of Biodiversity Losses The accelerated rate of species extinctions are largely due to human activities. • There are four major causes (called ‘The Evil Quartet’) of biodiversity losses: These are (i) Habitat loss and fragmentation, (ii) over exploitation, (iii) alien species invasions and (iv) co-extinction. BIODIVERSITY CONSERVATION Reasons for Conservation of Biodiversity There are many reasons, some are obvious and others are not so obvious: • The reasons for conservation of biodiversity can be grouped into following three categories. (i) Narrowly utilitarian reasons — These are obvious reasons. — H uman being derive countless direct economic benefit from nature such as food (cereals, pulses, fruits), firewood, fibre, construction material, industrial products (tannins, lubricants, dyes, resins, perfumes) and products of medicinal importance. — More than 25 per cent of the drugs are derived from plants and about 25000 species of plants are used by native people as traditional medicine. — Now more and more resources are put into bioprospecting (i.e., exploring molecular genetic and species level diversity for products of economic importance) to know the conomic use of plants. (ii) Broadly utilitarian — B iodiversity plays a major role in many ecosystem services provided by the nature. These include: (a) P roduction of oxygen, e.g. Amazon forests produce 20 per cent of the total oxygen in the earth’s atmosphere through photosynthesis. (b) P ollination of plants (through bees, bumble bees, birds and bats) without which they cannot give us fruits and seeds. (c) A esthetic pleasures of walking through thick woods, watching spring flowers in full bloom, waking up to a bulbul’s song in the morning etc. (iii) Ethical reasons — E very species has an intrinsic value, even if it may not be of current economic value to us. — We have a moral duty to care for their well being and pass on the biological legacy in a good order to future generations.

156 Biology-XII Conservation of Biodiversity • There are two approaches for conservation of biodiversity (i) in-situ Conservation (on site conservation) (ii) ex-situ Conservation (off site conservation) In situ Conservation When we conserve and protect the whole ecosystem, the biodiversity at all levels is protected, e.g. we save the entire forest to save the tiger; This approach is called in situ (on site) conservation. • Faced with the conflict between development and conservation, many nations find it unrealistic and economically not feasible to conserve all their biological wealth. • The conservationists, have identified for maximum protection certain regions called ‘biodiversity hotspots’ with high level of species richness and high degree of endemism (i.e., species confined to that region and not found anywhere else). • Out of 34 hotspots of biodiversity in the world, three are in India, i.e. Western Ghats and Sri Lanka, Indo-Burma and Himalayas. • Biodiversity hotspots cover less than 2 per cent of the earth’s land area, they harbour extremely high number of species and strict protection of these hotspots could reduce the ongoing mass extinction by almost 30 per cent. • In India, ecologically unique and biodiversity rich regions are legally protected as: (i) Biosphere reserves (ii) National parks (iii) Wildlife sanctuaries and (iv) Sacred groves (i) Biosphere reserves — These are large tracts of protected land with multiple use preserving the genetic diversity of representative ecosystem by protecting wildlife, traditional life styles of the tribals and varied plant and animal genetic resources. (ii) National parks — T hese are areas reserved for wildlife where they are able to obtain all the required natural resources and proper habitats. — Presently, India has 90 National Parks. (iii) Wildlife sanctuaries — T hese are tracts of land with or without lake where animals are protected from all types of exploitation and habitat disturbance. — At present, India has 448 wildlife sanctuaries. (iv) Sacred groves — These are tracts of forest set aside where all the trees and wildlife within are venerated and given total protection. — S uch sacred groves are found in Khasi and Jaintia Hills in Meghalaya; Aravali Hills of Rajasthan; Western Ghat regions of Karnataka and Maharashtra and the Sarguja; Chanda and Bastar area of Madhya Pradesh. — In Meghalaya, the sacred groves are the last refuges for a large number of rare and threatened plants.