NCERT Exemplar Class 12 Biology Solutions Chapter 8 Human Health and Disease

Question:2

The organisms which cause diseases in plants and animals are called:
a. Pathogens
b. Vectors
c. Insects
d. Worms

Answer:

Disease-causing organisms like certain bacteria, viruses, fungi, and protozoa are called pathogens. These are harmful and can affect both plants and animals.

Hence, the correct answer is option (a) Pathogens.

Question:3

The clinical test that is used for the diagnosis of typhoid is:
a. ELISA
b. ESR
c. PCR
d. Widal

Answer:

The Widal test is used to diagnose typhoid fever. It checks for antibodies in the patient's serum against the bacteria that cause typhoid.

Hence, the correct answer is option (d) Widal-Test.

Question:4

Diseases are broadly grouped into infectious and non-infectious diseases. In the list given below, identify infectious diseases.
i. Cancer
ii. Influenza
iii. Allergy
iv. Smallpox
(a) i and ii (b) ii and iii (c) iii and iv (d)ii and iv

Answer:

Infectious diseases spread from person to person and are caused by microbes. Influenza and smallpox are classic examples. Cancer and allergies are non-infectious.

Hence, the correct answer is option (d) (ii) and (iv).

Question:5

The sporozoites that cause infection when a female Anopheles mosquito bites a person, are formed in:
a. liver of the person
b. RBCs of mosquito
c. salivary glands of mosquito
d. gut of mosquito

Answer:

When a mosquito bites, it transfers sporozoites which are formed in its intestine. These enter the human bloodstream and cause malaria.

Hence, the correct answer is option (d) intestine of the mosquito.

Question:6

The disease chikungunya is transmitted by:
a. house fly
b. Aedes mosquito
c. cockroach
d. female Anopheles

Answer:

Chikungunya is spread by the bite of an Aedes mosquito. It is the same mosquito that spreads dengue as well.

Hence, the correct answer is option (b) Aedes mosquitoes.

Question:7

Many diseases can be diagnosed by observing the symptoms in the patient. Which group of symptoms are indicative of pneumonia?
a. Difficulty in respiration, fever, chills, cough, headache
b. Constipation, abdominal pain, cramps, blood clots
c. Nasal congestion and discharge, cough, constipation, headache
d. High fever, weakness, stomach pain, loss of appetite and constipation

Answer:

Pneumonia mostly affects the lungs. Symptoms include breathing difficulty, fever, chills, and cough. Digestive symptoms are not seen in this case.

Hence, the correct answer is option (a) Difficulty in respiration, fever, chills, cough, headache.

Question:8

Cancer-causing genes are called:
a. structural genes
b. expressed genes
c. oncogenes
d. regulatory genes

Answer:

Oncogenes are genes that, when mutated or expressed at high levels, can cause normal cells to become cancerous.

Hence, the correct answer is option (c) oncogenes.

Question:9

In malignant tumours, the cells proliferate, grow rapidly and move to other parts of the body to form new tumours. This stage of the disease is called:
a. metagenesis
b. metastasis
c. teratogenesis
d. mitosis

Answer:

In metastasis, cancer cells move from one part of the body to another and start forming tumours in other organs too.

Hence, the correct answer is option (b) metastasis.

Question:10

When a healthy person is diagnosed as unhealthy by a psychiatrist, the reason could be that:
a. the patient was not efficient at his work
b. the patient was not economically prosperous
c. the patient shows behavioural and social maladjustment
d. he does not take an interest in sports

Answer:

A person may look physically healthy but still show mental or social issues. In such cases, psychiatrists may find signs of behavioural or emotional problems.

Hence, the correct answer is option (c) the patient shows behavioural and social maladjustment.

Question:11

Which of the following is the reason(s) for Rheumatoid arthritis? Choose the correct option.
i. The ability to differentiate pathogens or foreign molecules from self-cells increases.
ii. The body attacks self cells
iii. More antibodies are produced in the body
iv. The ability to differentiate pathogens or foreign molecules from self cells is lost
(a) i and ii (b) ii and iv (c) iii and iv (d) I and iii

Answer:

In rheumatoid arthritis, the immune system wrongly attacks the body’s own cells. It happens when the ability to differentiate between self and non-self is lost.

Hence, the correct answer is option (b) (ii) and (iv).

Question:12

AIDS is caused by HIV. Among the following, which one is not a mode of transmission of HIV?
a. Transfusion of contaminated blood
b. Sharing the infected needles
c. Shaking hands with infected person
d. Sexual contact with infected persons

Answer:

HIV spreads through infected blood, body fluids, or from mother to child. Simple contact like shaking hands does not transmit the virus.

Hence, the correct answer is option (c) Shaking hands with infected persons.

Question:13

'Smack' is a drug obtained from the:
a. latex of Papaver somniferum
b. leaves of Cannabis sativa
c. flowers of Dhatura
d. fruits of Erythroxylum coca

Answer:

Smack is a drug derived from the latex of the opium poppy plant (Papaver somniferum). It is a strong narcotic.

Hence, the correct answer is option (a) latex of Papaver somniferum.

Question:14

The substances produced by a cell in a viral infection that can protect other cells from further infection are:
a. serotonin
b. colostrum
c. interferon
d. histamine

Answer:

Interferons are proteins made by cells in response to a virus. They help other nearby cells fight off infection.

Hence, the correct answer is option (c) interferon.

Question:15

Transplantation of tissues/organs to save certain patients often fails due to the rejection of such tissues/organs by the patient. Which type of immune response is responsible for such rejections?
a. auto-immune response
b. humoral immune response
c. physiological immune response
d. cell-mediated immune response

Answer:

Rejection of a transplanted organ is due to the immune system identifying it as foreign. This is called a cell-mediated immune response.

Hence, the correct answer is option (d) cell-mediated immune response.

Question:16

Antibodies present in colostrum which protect the newborn from certain diseases are of
a. IgG type
b. Ig A type
c. Ig D type
d. Ig E type

Answer:

IgA antibodies are found in colostrum, the first milk from the mother. They give immunity to the newborn against infections.

Hence, the correct answer is option (b) IgA type.

Question:17

Tobacco consumption is known to stimulate the secretion of adrenaline and nor-adrenaline. The component causing this could be:
a. Nicotine
b. Tannic acid
c. Curamin
d. Catechin

Answer:

Nicotine, found in tobacco, stimulates the nervous system and increases the release of adrenaline and nor-adrenaline.

Hence, the correct answer is option (a) Nicotine.

Question:18

Antivenom against snake poison contains:
a. Antigens
b. Antigen-antibody complexes
c. Antibodies
d. Enzymes

Answer:

Antivenom is made by injecting a small amount of venom into animals to produce antibodies. These antibodies are used to treat snake bites.

Hence, the correct answer is option (c) Antibodies.

Question:19

Which of the following is not a lymphoid tissue?
b. Tonsils
c. Pancreas
d. Thymus

Answer:

Lymphoid tissues help in immune responses. Pancreas, however, is a digestive gland and is not part of the lymphoid system.

Hence, the correct answer is option (c) Pancreas.

Question:20

Which of the following glands is large-sized at birth but reduces in size with ageing?
a. Pineal
b. Pituitary
c. Thymus
d. Thyroid

Answer:

The thymus gland is large at birth and plays a major role in developing immunity. It gradually shrinks with age.

Hence, the correct answer is option (c) Thymus.

Question:21

Haemozoin is a:
a. precursor of haemoglobin
b. the toxin released from Streptococcus-infected cells
c. the toxin released from Plasmodium-infected cells
d. the toxin released from Haemophilus-infected cells

Answer:

Haemozoin is a toxic substance released when Plasmodium infects red blood cells. It causes the fever pattern seen in malaria.

Hence, the correct answer is option (c) toxin released from Plasmodium-infected cells.

Question:22

Which of the following is not the causal organism for ringworm?
a. Microsporum
b. Trichophyton
c. Epidermophyton
d. Microsporum

Answer:

Ringworm is a fungal infection. Macrosporum is not a recognised fungus for causing ringworm. The others listed are correct.

Hence, the correct answer is option (d) Macrosporum.

Question:23

A person with sickle cell anaemia is
a. more prone to malaria
b. more prone to typhoid
c. less prone to malaria
d. less prone to typhoid

Answer:

Sickle-shaped RBCs provide natural resistance to malaria as the Plasmodium parasite cannot survive easily in these cells.

Hence, the correct answer is option (c) less prone to malaria.

Question:2

The immune system of a person is suppressed. In the ELISA test, he was found positive to a pathogen.
a. Name the disease the patient is suffering from.
b. What is the causative organism?
c. Which cells of the body are affected by the pathogen?

Answer:

(a) AIDS
(b) Human Immuno Deficiency Virus
(c) T-lymphocytes

Question:3

Where are B-cells and T-cells formed? How do they differ from each other?

Answer:

B-cells are formed in the bone marrow and are responsible for the production of antibodies. T-cells are formed in the thymus, and they help B-cells in the production of antibodies.

Question:4

Given below are the pairs of pathogens and the diseases caused by them. Which out of these is not a matching pair, and why?

Answer:

c) Microsporum causes ringworm and not filariasis.

Question:5

What would happen to the immune system, if the thymus gland is removed from the body of a person?

Answer:

The thymus is responsible for the maturation of lymphocytes and is one of the primary lymphoid organs. As enough T-cells are generated during the foetal stage (pre-birth), their removal does not impact immunity significantly. However, if thymus is removed during infancy, there may be some effect on the individual's immunity

Question:6

Many microbial pathogens enter the gut of humans along with food. What are the preventive barriers to protect the body from such pathogens? What type of immunity do you observe in this case?

Answer:

Most microbial pathogens are eliminated due to mucus secreted by the inner lining of the alimentary canal. Pathogens which survive it, are killed in the stomach due to the acidic pH.

Question:7

Why is the mother's milk considered the most appropriate food for a newborn infant?

Answer:

For a few days after birth, the mother's milk is rich in antibodies (IgA) which protects the infant against many diseases.

Question:8

What are interferons? How do interferons check infection of new cells?

Answer:

Interferon is a protein secreted by virus-infected cells, which acts as a cytokine barrier and protects other cells from infection.

Question:9

In the figure, the structure of an antibody molecule is shown. Name the parts A, B and C. Show A, B and C in the diagram.

Answer:

A: Antigen binding site, B: Light chain, C: Heavy chain

Question:10

If a regular dose of a drug or alcohol is not provided to an addicted person, he show some withdrawal symptoms. List any four such withdrawal symptoms.

Answer:

Four withdrawal symptoms that an addicted person shows are:

1. Anxiety

2. Shakiness

3. Nausea

4. Sweating

Question:11

Why is it that during changing weather, one is advised to avoid close, crowded and air-conditioned places like cinema halls etc.?

Answer:

Germs, which can cause infectious diseases to float in the air during changing weather. Their presence is especially high in closed, crowded, and air-conditioned places. This is why we should avoid such places during changing weather.

Question:12

The harmful allele of sickle cell anaemia has not been eliminated from the human population. Such afflicted people derive some other benefit. Discuss.

Answer:

People suffering from sickle cell anaemia are less prone to malaria. According to a report from the CDC, in areas with a higher number of cases of malaria, cases of sickle cell anaemia are also higher.

Question:13

Lymph nodes are secondary lymphoid organs. Explain the role of lymph nodes in our immune response.

Answer:

Microbes and antigens, which make their way into the lymph and tissue fields, are trapped by lymph nodes. These trapped antigens, in turn, activate lymphocytes, triggering the immune response.

Question:14

Why is an antibody molecule represented as H₂L₂?

Answer:

An antibody molecule is represented as H₂L₂ because they have four peptide chains -
a. Light Chains - These two chains are small
b.Heavy Chains -These two chains are long

Question:15

What does the term 'memory' of the Immune system mean?

Answer:

Our body gains immunity against certain pathogens after they attack the body for the first time. This is called the primary response and is characterised by low intensity.
However, when the same pathogens make their way in again, our immune system responds with higher intensity due to 'memory'. This more intense response is called a secondary response.

Question:16

If a patient is advised Anti-Retroviral Therapy, which infection is he suffering from? Name the causative organism.

Answer:

If a patient is advised Anti-Retroviral Therapy, he is likely to suffer from AIDS. Human Immunodeficiency Virus (HIV) is the causative organism.

Question:2

Differentiate between a benign tumour and a malignant tumour.

Answer:

Question:3

Do you consider passive smoking to be more dangerous than active smoking? Why?

Answer:

Although active smokers are at a higher risk of smoking-related diseases, passive smoking is still more dangerous than active smoking. It is because the person is not intentionally doing it, but is forced by his/her situation to inhale the smoke, while an active smoker is aware of the danger, they are in.

Question:4

"Prevention is better than cure". Comment.

Answer:

Prevention is better than cure as the cure entails various costs - physical, emotional, and monetary. It adds a huge financial burden to the individual's family. Prevention generally costs a fraction of the cure and also prevents loss in economic productivity.

Question:5

Explain any three preventive measures to control microbial infections.

Answer:

Three preventive measures to control microbial infections are:
(a) Avoiding contaminated food and water: Many infections spread through contaminated food and water and can be easily prevented by avoiding contaminated food and water.
(b) Preventing vectors: Some diseases spread through vectors like mosquitoes. These diseases can be prevented by putting a check on the breeding grounds for these vectors.
(c) Maintaining hygiene: Many diseases, like Coronavirus, are transmitted through water droplets that come out of our nose and mouth. Maintaining personal hygiene is the best way to avoid contracting such diseases

Question:6

In the given flow diagram, the replication of retrovirus in a host is shown. Observe and answer the following questions.

a. Fill in (1) and (2)
b. Why is the virus called retrovirus?
c. Can the infected cell survive while viruses are being replicated and released?

Answer:

1. 1: viral DNA is produced; 2: Viral RNA is produced by the host cell

2. A virus which has an envelope enclosing the RNA genome is called a retrovirus.

3. Yes.

Question:7

"Maintenance of personal and public hygiene is necessary for prevention and control of many infectious diseases". Justify the statement by giving suitable examples.

Answer:

Maintaining personal hygiene ensures the non-transmission of many infectious diseases to a great extent. Especially diseases which transmitted through air, droplets, and skin infections.
Lack of public hygiene is the biggest contributor to the spread of many diseases like cholera, typhoid, malaria and many more. Ensuring the cleanliness of your surroundings can lead to a drastic reduction in incidence of many such diseases.

Question:8

The following table shows certain diseases, their causative organisms and symptoms. Fill the gaps.

Answer:

Question:9

The outline structure of a drug is given below.
a. Which group of drugs does this represent?
b. What are the modes of consumption of these drugs?
c. Name the organ of the body, which is affected by the consumption of these drugs.

Answer:

1. Cannabinoids

2. Inhalation and oral ingestion

3. Cardiovascular system

Question:10

Give the full form of CT and MRI. How are they different from each other? Where are they used?

Answer:

Question:11

Many secondary metabolites of plants have medicinal properties. It is their misuse that creates problems. Justify the statement with an example.

Answer:

Drugs like morphine and codeine (opium) have strong medical applications where morphine is a very strong painkiller, and codeine is effective in suppressing cough. Unfortunately, the flip side to both these medicines is that they are highly intoxicating and thus are misused for this purpose. Such drug abuse makes a person hallucinogenic.

Question:12

Why are cannabinoids banned in sports and games?

Answer:

Cannabinoids are used as a performance enhancer in sports as they reduce the sensation of pain and thus increase the endurance of the athlete.

Question:13

What is secondary metabolism?

Answer:

There are some pathways and small-molecule products of metabolism which are not essential for the survival of the organism. These are known as secondary or specialised metabolism.

Question:14

Drugs and alcohol give short-term 'high' and long-term 'damage', Discuss.

Answer:

Drugs and alcohol are intoxicating, and people use them to get 'high' but have serious long-term repercussions. Ex- Liver cirrhosis (a life-threatening ailment) is common among long-term alcohol addicts.

Question:15

Diseases like dysentery, cholera, typhoid, etc., are more common in overcrowded human settlements. Why?

Answer:

It is tough to maintain public hygiene in overcrowded places. Consider, for example, Shared washrooms are common in overcrowded places. Compared to an individual's washroom, such washrooms will be highly unhygienic. Moreover, being densely populated, even simple diseases like the common cold spread to many people very quickly.

Question:16

From which plant are cannabinoids obtained? Name any two cannabinoids. Which part of the body is affected by consuming these substances?

Answer:

Cannabinoids are obtained from Cannabis sativa. Marijuana and hashish are examples of cannabinoids. They affect the cardiovascular system.

Question:17

In the metropolitan cities of India, many children are suffering from allergies/asthma. What are the main causes of this problem? Give some symptoms of allergic reactions.

Answer:

Many children are protected from the external environment early in their life because of which their immunity is low against hazardous environmental factors, especially in metropolitan areas. This is the main cause of allergic reactions in children. Some symptoms of an allergic reaction are; coughing, sneezing, breathlessness, etc.

Question:18

What is the basic principle of vaccination? How do vaccines prevent microbial infections? Name the organism from which the hepatitis B Vaccine is produced.

Answer:

Vaccination works on the principle of 'memory' of the immune system. Vaccines help the immune system to fight future attacks from a pathogen. Antibodies are created by the body in response to the vaccine, and these antibodies jump into action when the pathogen attacks again. Yeast is used to produce the Hepatitis B vaccine.

Question:19

What is cancer? How is a cancer cell different from a normal cell? How do normal cells attain a cancerous nature?

Answer:

Uncontrolled cell division which leads to the formation of a tumour, is called cancer. Unlike a normal cell, which loses its ability to divide in a few iterations, cancer cells continue to divide endlessly. Generally, the normal cell stops dividing when it comes in contact with other cells. This ability is known as contact inhibition, and cancerous cells are abnormal as they do not possess this ability.

Question:20

A person shows strong, unusual hypersensitive reactions when exposed to certain substances present in the air. Identify the condition. Name the cells responsible for such reactions. What precautions should be taken to avoid such reactions?

Answer:

This condition is called an allergy. Such a reaction is caused by mast cells and basophils (white blood cells). To prevent such allergic reactions, one should avoid the substances to which they are allergic. Allergies against pollen are very common, and an allergic person should avoid going near such flowers.

Question:21

For an organ transplant, it is an advantage to have an identical twin. Why?

Answer:

The immune system always tries to reject any foreign substance. Unfortunately, this may lead to tissue rejection in Organ transplants. However, most of the tissues are identical in identical twins, and this reduces the chances of tissue rejection.

Question:22

What are lifestyle diseases? How are they caused? Name any two such diseases.

Answer:

Lifestyle diseases occur because of faulty lifestyles. Overeating and a sedentary lifestyle are the major causes of such diseases. Ex-Diabetes and hypercholesterolemia.

Question:23

If there are two pathogenic viruses, one with DNA and the other with RNA, which would mutate faster? And Why?

Answer:

Compared to DNA, RNA replication is more susceptible to errors and thus more susceptible to mutations.

Question:2

Compare the lifestyle of people living in urban areas with those of rural areas and briefly describe how lifestyle affects their health.

Answer:

Question:3

Why do some adolescents start taking drugs? How can this be avoided?

Answer:

Many adolescents who start taking drugs do so because of their curiosity and adventure-seeking nature. Moreover, under peer pressure, many adolescents end up taking drugs to experiment, and continued use leads to addiction.

Question:4

In your locality, if a person is addicted to alcohol, what kind of behavioural changes do you observe in that person? Suggest measures to overcome the problem.

Answer:

A person addicted to alcohol may avoid socialising, may become easily irritable and suffer from spells of rage and depression. Some people even resort to petty crimes if they are unable to afford the money to buy alcohol.
To address the situation:

• A qualified counsellor should be pressed into service.

• People closest to them should spend more time with the person

• The person must get help to reduce or totally withdraw from any alcohol consumption

Question:5

What are the methods of cancer detection? Describe the common approaches for the treatment of cancer.

Answer:

The following are the methods of cancer detection:

• Biopsy: A small fragment of the concerning tissue is extracted and then goes through histopathological study.
• Blood Test and Bone Marrow Test: Increased levels of cell count can be gauged from this test.
• Imagery Technique: Internal organs can be diagnosed by X-ray, CT scan and MRI.
  Apart from the above-mentioned techniques, antibodies against cancer-specific antigens and molecular biotechnology are also used in certain cases.
  Common approaches of treatment involve surgery, radiotherapy, and immunotherapy:

• Surgery: It can be used to remove the tumour.

• Radiotherapy: Radioactive rays can be utilised to destroy cancerous cells, with minimal impact on normal cells

• Immunotherapy: Chemotherapeutic drugs are used to destroy cancer cells. It involves the use of Interferon alfa, which helps the body's immune system to respond to cancer.

Question:6

Drugs like LSD, barbiturates, amphetamines, etc., are used as medicines to help patients with mental illness. However, excessive doses and abusive usage are harmful. Enumerate the major adverse effects of such drugs in humans.

Answer:

Adverse Effects of LSD: The most common side effect of LSD is depression. Other side effects include Schizophrenia or severe uterine contractions (in females)
Adverse Effects of Barbiturates: Side effects of Barbiturates include -

• Tolerance - The person needs higher doses as time passes

• Dependence - A person cannot live without this drug.

Adverse Effects of Amphetamines: Mental depression and bouts of hallucinations are common side effects.

Question:7

What is the Pulse Polio Programme of the Government of India? What is OPV? Why is it that India is yet to eradicate Polio?

Answer:

Pulse Polio: Launched in 1995-96, it is a mass immunisation programme aimed at eradicating the poliomyelitis virus from India. This programme has been undertaken with active cooperation from government agencies, NGOs, UNICEF, and the CDC(Centres for Disease Control and Prevention)
Key Objectives of Pulse Polio:

• Not a single child should be missed.

• High level of surveillance.

• Reporting of any new case within 14 days.

To cover all the children below age 5, Polio booths are established throughout the country, and volunteers are hired to administer the polio vaccine.
OPV (Oral Polio Vaccine): OPV is an attenuated vaccine, which is produced at a sub-physiological temperature by the passage of the virus through non-human cells. This produces a spontaneous mutation in the viral genome. A single vial of OPV usually contains 10-20 doses.
India was declared a polio-free nation on 27th March 2014, as there were no new cases in the previous three years.

Question:8

What are recombinant DNA vaccines? Give two examples of such vaccines. Discuss their advantages.

Answer:

In a recombinant DNA vaccine, only one or two antigens are inserted into the DNA of a suitable host. Recombinant DNA technology enables to making of vaccines on a larger scale with the least chance of contamination. These are cheaper. Examples include Hepatitis B and the HPV Vaccine.
Cell culture is used to do large-scale production. A suitable animal (ex-horse) is injected with strains of the pathogen, and antigens are produced in the horse's cells. Antigens are then extracted from the horse's serum. However, there are many shortcomings to this method –

• Due to the possibility of contamination, there is are chance of contracting other diseases

• The method is challenged by Animal Rights Activists.

Recombinant DNA technology can address these issues, as yeast is required to produce the vaccine, and large-scale production can be done at a lower cost.