Human Health and Diseases HOTs Class 12 Biology

HOTs for Class 12

Please refer to Human Health and Diseases HOTs Class 12 Biology provided below with solutions. All HOTs for Class 12 Biology with answers provided below have been designed as per the latest syllabus and examination petter issued by CBSE, NCERT, KVS. Students of Standard 12 Biology should learn the solved HOTS for Class 12 Biology provided below to gain better marks in examinations.

Human Health and Diseases Class 12 Biology HOTs

Common Diseases in Humans

Very Short Answer Type Questions

Question. Recently chikungunya cases were reported from various parts of the country. Name the vector responsible. 
Answer. Aedes aegypti

Question. How does haemozoin affect the human body when released in blood during malarial infection?
Answer.Haemozoin is a toxic substance released by rupturing of RBCs into blood during malarial infection. It causes chill and high fever recurring every 3-4 days.

Question. Name the two intermediate hosts which the human liver fluke depends on to complete its life cycle so as to facilitate parasitisation of its primary host. 
Answer. Snail and fish.

Short Answer Type Questions

Question. Name the host and the site where the following occur in the life-cycle of a malarial parasite:
(a) formation of gametocytes
(b) fusion of gametocytes. 
Answer.(a) Formation of gametocytes takes place in human host in red blood cells.
(b) Fusion of gametocytes takes place in mosquito, in its stomach.

Question. Name the parasite that causes fllariasis in humans. Mention its two diagnostic symptoms.How is this disease transmitted to others?
Answer. Filariasis is a helminthic disease caused by Wuchereria (W. bancrofti and W. malayi). It causes swelling of lymphatic vessels of lower limbs resulting in swelling of feet, legs, scrotal sacs and thighs. It spreads from one human being to other through the bite of female mosquito, Culex.

Question. A patient showed symptoms of sustained high fever, stomach pain and constipation, but no blood clot in stools. Name the disease and its pathogen. Write the diagnostic test for the disease. How does the disease get transmitted?
Answer. Bacterial disease typhoid, caused by Salmonella typhi is characterised by sustained high fever (39° – 40°C), stomach pain and constipation. Typhoid fever is diagnosed by Widal test and is transmitted through contaminated food and water.

Question. Name the causative organism, two symptoms and mode of transmission of amoebiasis.
Answer. Entamoeba histolytica is a protozoan parasite in the large intestine of human which causes amoebiasis (amoebic dysentery). Symptoms of this disease include diarrhoea alternating with constipation, abdominal pain and cramps, stool with excess mucus and blood clots. Houseflies act as mechanical 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 is the main source of infection.

Question. List the symptoms of ascariasis. How does a healthy person acquire this infection?
Answer. Ascariasis is caused by the common round worm Ascaris lumbricoides, a giant intestinal worm. Symptoms of this disease include internal bleeding, muscular pain, fever, anemia and blockage of the intestinal passage. A healthy person acquires infection through contaminated water, vegetables, fruits, etc.

Question. (a) Name the causative organisms for the following diseases:
(i) Elephantiasis,
(ii) Ringworm,
(iii) Amoebiasis
(b) How can public hygiene help control such diseases? 
Answer.(a) (i) Elephantiasis – Wuchereria bancrofti
(ii) Ringworm – Microsporum
(iii) Amoebiasis – Entamoeba histolytica
(b) Maintenance of public hygiene is very important for prevention and control of many infectious diseases. Public hygiene includes proper disposal of waste and excreta, periodic cleaning and disinfection of water reservoirs, pools, and tanks and observing standard practices of hygiene in public catering.
These measures are particularly essential where the infectious agents are transmitted through food and water such as typhoid, amoebiasis and ascariasis.

Question. Give the scientific name of the parasite that causes malignant malaria in humans. At what stage does this parasite enter the human body? Trace its life cycle in human body. 
Answer. Malignant malaria is caused by Plasmodium falciparum.
The malarial parasite, Plasmodium enters the human body as sporozoites (infectious form) through the bite of infected female Anopheles mosquito (vector). From the human blood sporozoites enter liver cells and multiply here and then attack the red blood cells (RBCs) resulting in their rupture. The rupture of RBCs is associated with release of a toxic substance, haemozoin, which is responsible for the chill and high fever recurring every three to four days. The released parasites from the ruptured RBCs infect new RBCs and develop into gametocytes (male and female). When a female Anopheles mosquito sucks the blood of an infected human host, it receives RBCs containing gametocytes.

Question. Mention any two human diseases caused by round worms. Name their causative agents and their mode of transmission into the human body. 
Answer. Round worms are nematodes, responsible for helminthic diseases in humans.
Two human diseases caused by round worms are :
(i) Ascariasis – It is caused by Ascaris lumbricoides and spreads through contaminated fruits, water, vegetables etc.
(ii) Filariasis – It is caused by Wuchereria bancrofti, and W. malayi. It is transmitted by the bite of female Culex mosquito.

Question. (a) Name the respective forms in which the malarial parasite gains entry into
(i) human body and
(ii) body of female Anopheles.
(b) Name the hosts where the sexual and the asexual reproductions of malarial parasite occur respectively.
(c) Name the toxin responsible for the appearances of symptoms of malaria in humans.
Why do these symptoms occur periodically?
Answer.(a) (i) Sporozoites,
(ii) Gametocytes
(b) Sexual phase of malarial parasite occurs in the mosquito, the primary host of malarial parasite and asexual phase occurs in man, the secondary host.
(c) The release of merozoites and toxin haemozoin from the bursting of schizont in RBCs causes chill and high fever. The released merozoites then attack fresh RBCs leading to the formation of trophozoites causing decrease in fever. The trophozoites then grow in size to become schizont that causes increase in temperature. The schizonts again develop merozoites inside themselves thus causing recurrence of fever with the release of merozoites after few days e.g. at regular intervals of 48 hours in case of P. vivax malaria.


Very Short Answer Type Questions

Question. How does HIV differ from a bacteriophage?
Answer. HIV has single stranded RNA as genetic material, while bacteriophage has dsDNA.

Question. Why sharing of injection needles between two individuals is not recommended? 
Answer. Sharing of injection needles between two individuals can transmit various diseases like AIDS and hepatitis B, as these diseases are transmitted via blood and semen.

Question. Name the two types of cells in which the HIV multiplies after gaining entry into human body.
Answer. Macrophages and helper T cells.

Question. What type of virus causes AIDS? Name its genetic material. 
Answer. AIDS is caused by human immunodeficiency virus (HIV), a retrovirus. It has ssRNA as genetic material.

Question. Retroviruses have no DNA. However, the DNA of the infected host cell does possess viral DNA.How is it possible? 
Answer. Retroviruses have RNA as their genome. RNA genome of virus replicates in host cell to form viral DNA with the help of reverse transcriptase enzyme.

Question. Name the type of cells the AIDS virus enters into after getting in the human body.
Answer. AIDS virus, HIV enters into macrophages after entering into human body.

Short Answer Type Questions

Question.Name the cells that act as HIV factory in humans when infected by HIV. Explain the events that occur in the infected cell.
Answer.Macrophages act as HIV factory in humans.
Events that occur in infected cells are:
(i) After the entrance of the virus into the body of the person, the virus enters into macrophages where RNA genome of the virus replicates to form viral DNA with the help of reverse transcriptase enzyme.
(ii) Viral DNA gets incorporated into the host cell’s DNA and directs the infected cells to produce viruses.
(iii) Simultaneously HIV virus enters into helper T lymphocytes where it replicates and produces more viruses. This is repeated so that the number of helper T lymphocytes decreases in the body of the infected person.
(iv) Due to decrease in the number of helper T lymphocytes in the body, the person starts suffering from infections and gets immune deficiency and he/ she is unable to protect himself/herself against these infections.

Question. (a) Name the group of viruses responsible for causing AIDS in humans. Why are these viruses so named?
(b) List any two ways of transmission of HIV infection in humans, other than sexual contact.
Answer.(a) AIDS is caused by human immunodeficiency virus (HIV), a member of a group of viruses called retroviruses. These viruses are called retroviruses because they have RNA as their genome, enclosed within an envelope.
(b) Other than sexual contact, transmission of HIV infection in humans could also occur by
(i) Transfusion of contaminated blood and blood products.
(ii) From infected mother to her child through placenta.

Short Answer Type Questions

Question. Study the diagram showing replication of HIV in humans and answer the following questions accordingly.

Human Health and Diseases HOTs Class 12 Biology

(a) Write the chemical nature of the coat ‘A”.
(b) Name the enzyme ‘B’ acting on ‘X’ to produce molecule ‘C’. Name ‘C’.
(c) Mention the name of the host cell ‘D’ the HIV attacks first when it enters into the human body.
(d) Name the two different cells the new viruses ‘E’ subsequently attack. 
Answer.(a) A – Protein coat
(b) B – Reverse transcriptase
C – Viral DNA
(c) D – Macrophage
(d) E – Macrophages and T-lymphocytes

Long Answer Type Questions

Question. A person in your colony has recently been diagnosed with AIDS. People/residents in the colony want him to leave the colony for the fear of spread of AIDS.
(a) Write your view on the situation, giving reasons.
(b) List the possible preventive measures that you would suggest to the residents of your locality in a meeting organised by you so that they understand the situation.
(c) Write the symptoms and the causative agent of AIDS. 
Answer.(a) An AIDS patient should not be forced to leave the society because AIDS cannot be transmitted by following methods :
(i) insect bites, (ii) crowded transport, (iii) shaking hands, (iv) sharing towels, (v) coughing and sneezing,(vi) kissing and embracing, (vii) sharing utilities and telephone, (viii) swimming pools and toilets.
(b) I would try to educate the residents about the cause of spread of AIDS emphasising that it is caused by sexual contact with infected person, through infected needles and blood transfusion. Therefore,the preventive measures would be to avoid multiple sexual partners, use disposable needles and condoms.
(c) The symptoms of HIV infection include fever, lethargy, pharyngitis, nausea, headache, rashes, swollen lymph nodes etc. The causative agent of AIDS is human immunodeficiency virus (HIV).


Very Short Answer Type Questions

Question. Indiscriminate diagnostic practices using X-rays etc., should be avoided. Give one reason.
Answer.Indiscriminate use of X-rays can cause DNA damage leading to neoplastic transformation. 

Short Answer Type Questions

Question. Why are the tumors cells dangerous?
Answer.Tumor cells are dangerous, as they have lost the property of contact inhibition and shows uncontrolled growth. Tumor cells invade and destroy the surrounding tissues.

Question. (a) Explain the property that prevents normal cells from becoming cancerous.
(b) All normal cells have inherent characteristic of becoming cancerous. Explain.
(a) Contact inhibition is the property that prevents normal cells from becoming cancerous. Due to this property they contact with other cells which inhibits their uncontrolled growth, thus prevent them from becoming cancerous.
(b) Cancerous growth of normal cells is due to loss of contact inhibition and programmed cell death, which keep their number constant. Due to loss of these properties, normal cells become cancerous.

Question. Differentiate between benign and malignant tumors. 
Answer.Comparison between benign tumor and malignant tumor is as follows :

Human Health and Diseases HOTs Class 12 Biology

Question. Why do normal cells not show cancerous growth? 
Answer.Normal cells have a limited life span. Their production is regulated in such a manner that number of given cell type remains nearly constant.
These cells also show property of contact inhibition, which inhibit their uncontrolled growth.

Short Answer Type Questions

Question. (a) What makes some viruses cause cancer in humans?
(b) How do benign tumors turn malignant?
How does the latter harm the human body?
Answer.(a) Cancer causing viruses are called oncogenic viruses. The genes of oncogenic viruses are known as viral oncogenes which could lead to oncogenic transformation of cells, causing cancer.
(b) Abnormal increase in number of cells in a tissue or organ forms a clone of proliferative cells. This excessive proliferation gives rise to a mass of cells which is initially known as benign tumour. The benign tumour cells sometimes enter into the blood vessels and migrate to other sites in the body where these cells continue to divide and start a new tumour there, such tumour cells are known as malignant cells and tumours are called malignant tumours. The malignant tumours are designated as cancer. The malignant tumors damage normal cells and compete with them for vital nutrients and disrupt the normal metabolism.

Long Answer Type Questions

Question. (a) Cancer is one of the most dreaded disease.Explain ‘contact inhibition’ and ‘metastasis’ with respect to the disease.
(b) Name the group of genes that have been identified in normal cells that could lead to cancer. How do these genes cause cancer?
(c) Name any two techniques that are useful in detecting cancers of internal organs.
(d) Why are cancer patients often given a-interferon as part of the treatment?
(a) The normal cells are characterised by contact inhibition by virtue of which contact with other cells inhibits their uncontrolled growth. Metastasis is a property shown by cancerous cells in which these cells detach from the tumours and move to distant sites through body fluids and develop secondary tumours. Metastasis is fatal because the cancerous cells damage other normal cells, compete with them for vital nutrients and disrupt the normal metabolism.
(b) Several genes called cellular oncogenes (c-onc) or proto oncogenes have been identified in normal cells which, when activated under certain conditions, could lead to oncogenic transformation of the cells (cancer).
(c) Radiography (X-rays) and CT (computerised tomography) are useful in detecting cancer of internal organs.
(d) The cancer patients are given substances called biological response modifiers such as a-interferon which activate their immune system and helps in destroying the tumour.

Drugs and Alcohol Abuse

Very Short Answer Type Questions

Question. How does smoking tobacco in humans lead to oxygen deficiency in their body? 
Answer.Smoking tobacco increases carbon monoxide content in blood and reduces concentration of haembound oxygen, which causes oxygen deficiency in the body.

Short Answer Type Questions

Question. Identify A, B, C and D in the following table:

Human Health and Diseases HOTs Class 12 Biology

Answer.A – Heroine
B – Cardiovascular system
C – Cocaine
D- Central nervous system

Question. Write the scientific name of the source plant of the drugs, marijuana and hashish and mention their effect on the human body. 
Answer.Drugs, marijuana and hashish are obtained from Cannabis sativa. Being hallucinogenic, they give feeling of well being and happiness. Sometimes, marijuana causes uncontrolled laughter and dilation of pupil.

Question. List four reasons to justify the ban on intake of cannabinoids by sportspersons. 
Answer.The intake of cannabinoids by sportspersons should be banned due to following reasons: (i) They have a potent stimulating action on the central nervous system causing hallucinations.
(ii) They produce a sense of euphoria and increased energy and hence, sportspersons become addicted to them.
(iii) They delay fatigue.
(iv) They increase blood sugar level and frequency of urination.

Question. What is ‘withdrawal syndrome’? List any two symptoms it is characterised by.
Answer.Withdrawal syndrome is group of symptoms that occur in drug and alcohol addicted individuals who abruptly discontinue or reduce the use of drug of their choice. Withdrawl symptoms include anxiety and nausea.

Question. Name the plant source of ganja. How does it affect the body of the abuser?
Answer.Ganja is obtained from Cannabis sativa. It is hallucinogenic. It alters thoughts, feelings and perceptions and causes illusions.

Question. Why is using tobacco in any form injurious to the health? Explain. 
Answer. Smoking of tobacco is associated with cancer of lungs, urinary bladder and throat, bronchitis, emphysema, coronary heart diseases, etc. Smoking also increases the CO content in blood and reduces the concentration of haembound oxygen, thus causing oxygen deficiency in the body. Chewing of tobacco causes cancer of oral cavity. Nicotine, an alkaloid present in tobacco, stimulates the adrenal glands to secrete adrenaline and noradrenaline, which increase the blood pressure and heart rate.

Question. Name the plant source of the drug popularly called ‘smack’. How does it affect the body of the abuser? 
Answer.Smack is an opioid narcotic, obtained from poppy plant, Papaver somniferum. It is a powerful analgesic and relieves the pain by acting on central nervous system.

Question. Why do sports persons often fall a victim to cocaine addiction?
Answer. Sportspersons often become addicted to cocaine, to enhance their performance. Cocaine is a stimulant that increases heart beat, blood pressure, body temperature and delays fatigue. Sportspersons take drugs to promote aggressiveness and to increase athletic performance.

Short Answer Type Questions

Question. A team of students is preparing to participate in the interschool sports meet. During a practice session you find some vials with labels of certain cannabinoids.
(a) Will you report to the authorities? Why?
(b) Name a plant from which such chemicals are obtained.
(c) Write the effect of these chemicals on human body. 
Answer.(a) Yes, I will report to authorities because cannabinoids are drugs and drug abuse is an illegal practice.
(b) Cannabis sativa
(c) Cannabinoids alter thoughts, feelings and perceptions. These drugs cause illusions.

Question. Write the source and the effect on the human body of the following drugs:
(a) Morphine
(b) Cocaine
(c) Marijuana 
Answer. (a) Morphine – It is obtained from Papaver somniferum. It is strong analgesic and has sedative and calming effect. It decreases blood pressure and depresses respiratory centre.
(b) Cocaine – It is obtained from Erythroxylum coca. It has vasoconstrictor properties and is powerful CNS stimulant. Its excessive dosage causes hallucinations.
(c) Marijuana – It is obtained from Cannabis sativa. It is a hallucinogen and may cause psychosis.

Question. Do you support ‘Dope’ test being conducted on sportspersons participating in a prestigious athletic meet? Give three reasons in support of your answer.
Answer.Yes, Dope test should be conducted on sportspersons participating in athletic meet because:
(i) Athletes intake cannabinoids to increase their muscle tone and to have better performance.
(ii) Intake of cocaine alters cardiovascular functions, increases heart beat and blood pressure.
(iii) Cocaine delays fatigue and helps to enhance performance.

Question. (a) Name a drug used (i) as an effective sedative and pain killer (ii) for helping patients to cope with mental illnesses like depression, but often misused.
(b) How does the moderate and high dosage of cocaine affect the human body?
Answer.(a) (i) Morphine (ii) Barbiturates
(b) Cocaine taken in low dose induces sense of well being and pleasure and delays fatigue, but in high dosage, it causes hallucinations.

Question. “Prevention is better than cure” is an apt slogan to safeguard adolescents from drug abuse. List any 6 steps that could be taken in this regard.
Yes, it is always better to prevent the adolescents from being getting addicted to harmful drugs, rather than cure them for addiction. Six steps that could be taken in this regard are:
(i) A child should not be pushed unduly to perform beyond his/her threshold limits in studies, sports or any other activities.
(ii) Educating and counselling him/her to face problems and stresses and accept disappointments and failures as part of life.
(iii) Parents and teachers can identify the danger signs and take appropriate steps to diagnose the malady and underlying causes, so that proper remedial steps can be taken.
(iv) Help can/should be sought from qualified psychologists and psychiatrists.
(v) The individual can seek help from parents and teachers.
(vi) Help can also be sought from close and trusted friends; this would help to vent the feelings and anxiety and guilt.

Question. Prior to a sports event, blood and urine samples of sports persons are collected for drug tests.
(a) Why is there a need to conduct such tests?
(b) Name the drugs the authorities usually look for.
(c) Write the generic names of two plants from which these drugs are obtained.
(a) It is necessary to conduct such tests on sportspersons because they take various drugs like cocaine/coca alkaloids and cannabinoids to increase their muscle tone and performance in sports.
(b) Cocaine/coca alkaloids and cannabinoids.
(c) Cannabinoids are obtained from Cannabis sativa and cocaine is obtained from Erythroxylum coca.

Long Answer Type Questions

Question. An active member of an awareness group conducts regular programmes to sensitise public against alcoholism amongst youth-a serious health hazard in his locality.
Identify the values this member of the group is trying to propagate amongst the people in his locality.
He must be trying to make the people aware of the immediate ill-effects of alcoholism like reckless behavior and vandalism and how the excess dose can lead to cirrhosis, cerebral haemorrhage, heart failure, infertility and death due to respiratory failure. Alcoholism can lead to aggressive and rebellious behaviour, deteriorating relationship with family and friends, loss of interest in hobbies, weight loss/gain etc. The far-reaching implications are : (i) stealing, when the abuser is unable to get money to buy alcohol/drugs, (ii) causing mental and financial distress to his/her family, friends, etc. To avoid all these and to motivate the youth to live a happy and healthy life must be the aim of his counselling.

Question. You have attended a birthday party hosted by one of your classmates. You found some guests at the party sitting in a corner making a lot of noise and consuming ‘something’. After a while one of the boys from the group started screaming, behaving abnormally and sweating profusely. On enquiry you found that the group members were taking drugs.
(a) Would you inform your parents/school authorities? Yes/No. Give reasons in support of your answer.
(b) Prepare a note to be circulated amongst the schoolmates about the sources and dangers of any two drugs.
(c) Write any two ways you will suggest to your school principal so as to promote awareness amongst the youth against the use of these drugs. 
Answer.(a) Yes, I would inform the parents/school authorities, as taking drugs is an illegal practice .Also, teachers and parents can educate and counsel them properly and can make them understand the illeffects of taking these drugs.

Human Health and Diseases HOTs Class 12 Biology
Human Health and Diseases HOTs Class 12 Biology

(c) (i) The principal can arrange for counselling by psychiatrists, psychologists, etc. Professionals can address the students regarding drug addiction, its immediate and future consequences.
(ii) He can get posters showing ill effects of using drugs pasted on the walls of the school or can arrange for a play based on drug addiction to be shown to the students.