Penicillin is an antibiotic obtained from the fungus ‘Penicillium notatum’ and it works against bacteria. Quinine and chloroquine are drugs which are used to treat malaria. Anti-Tetanus Serum (ATS) is a vaccine used to prevent tetanus. None of these is obtained from fungus and hence, they are not antibiotics.

SARS is caused by bacteria (i.e. 1 is correct), AIDS is caused by Human Immunodeficiency Virus (HIV) (i.e. 2 is correct) and common cold is caused by different kinds of viruses (i.e. 4 is also correct). (1), (2) and (4) are correctly matched, but (3) is incorrect because malaria is caused by a protozoan, i.e. Plasmodium is transmitted by the vector, i.e. female anopheles mosquitoes.

A defective gene that leads to a defect is a factor which is present inside the body cells of an organism. Hence, it is an internal factor. Extrinsic factors are those which are outside of the body and they include causative agents, diet, community, social system, etc.

Most of the skin infections are caused by fungi. For example, ringworms. Bacteria and viruses cause internal infections like TB, influenza, etc. Mosquitoes can cause rashes on skin (it is not a disease) and may also transmit other diseases (not related to skin). Thus, (1), (2) and (3) are not suitable. So, only (4) is correct.

Bacterial diseases are those diseases that are caused and transmitted by different bacteria. Typhoid, cholera and tuberculosis are caused by bacteria namely Salmonella typhii, Vibrio cholera and Bacillus calmettie, respectively. Dengue fever is caused by a virus, which is transmitted by the vector Aedes mosquito. Hence, option (3) is the correct answer.

Headache, diarrhoea and common cold last for some time and affect us severely for that short period. But they do not leave any of the effects like weakness. Thus, these are acute diseases. On the contrary, tuberculosis is chronic because it affects us for a long time and also makes the body weak, even after the infection is cured. It is caused due to bacteria and in this disease, the lungs and the respiratory system are affected. In this, mucus begins to collect in lungs, gradually leading to inefficient gaseous exchange, frequent cough and even bleeding in the throat at later stages. Hence, option (4) is the correct answer.

Haemophilia is a disease in which the blood does not clot whenever there is a wound/injury and it is a genetic disorder. It is not caused or spread by infectious agents. Thus, it is a non-infectious disease. Cholera, typhoid and malaria are caused due to microorganisms, which cause infection or disease in the digestive system, immune system and blood (also liver), respectively.

(a) Acute diseases: These diseases are severe, but short-spanned and get less time to cause prolonged poor health. (b) Chronic diseases: These diseases last for longer periods of time and take sufficient time to affect different parts of the body and lead to a poor health, which recovers after a long time. (c) Infectious diseases: These diseases spread from a diseased person to a healthy person due to the transmission of disease-causing organisms (for example, common cold). (d) Non-infectious diseases: These diseases do not spread from one person to another. For example, heart ailment, cancer, etc. They are not caused by infectious agents. The causative agents of these diseases are internal factors. 

“Health” refers to physical and mental well-being. If a person has psychological tension, his mental stability is disturbed. In this situation, we may say that he is unhealthy. Being wise or wealthy has no relation (under scientific logic) with health. Unhealthy people can also be rich and wise.

Sickle cell anaemia is a genetic disorder in which the haemoglobin is defective and not efficient in O₂ transport. This defective haemoglobin distorts the shape of RBC in which it is stored and they look sickle-shaped. Hence, the name “sickle cell” is derived. Being sickle shaped, it is difficult for the RBCs to move more freely in the blood vessels and so supply of oxygen to different organs and cells become slow and hence, respiration and release of energy becomes low, thereby making us feel lethargic. 

Feeling anxiety at odd times is a sign of poor mental health. In such a situation, even if the person is physically fit, he is called unhealthy. So, (3) is the correct answer. “Happy” is an abstract feeling or state of mind which cannot be measured on scientific grounds. In general, being happy leads to good health. So, options (1), (2) and (4) are incorrect.

Disease causing organisms, i.e. causative agents are transferred from the diseased to the healthy person by an organism which itself does not get the disease. Such an agent is called a “vector”.

Infectious agents of common cold (virus), pneumonia (bacteria) and tuberculosis (bacteria) are the microbes which transfer through air, i.e. these are air borne diseases and affect our immune system, lungs and respiratory system, respectively. On the contrary, AIDS is caused due to HIV which is transmitted by sexual contact or exchange of body fluids only. Thus, (2) is the answer.

To protect themselves from adverse conditions, bacteria thicken or develop cell wall over their body. Cell membrane, i.e. plasma membrane cannot become thick enough to give protection while spores are the result of thickness and they germinate later.

AIDS, common cold and dengue fever are caused by viruses, e.g. HIV, common cold virus and dengue virus, respectively. Tuberculosis is caused by a bacterium named Bacillus calmettie and hence, (2) is the required answer.

Haemophilia is a genetic disease in which the blood does not clot. It is caused due to an error of DNA and the error is present on X chromosome but it is expressed in males only. Sickle cell anaemia is a genetic disorder in which the haemoglobin is defective and not efficient in O2 transport. This defective haemoglobin distorts the shape of RBC’s in which it is stored and they look sickle-shaped. Hence, the name “sickle cell” is derived. Being sickle shaped, it is difficult for the RBC’s to move freely in the blood vessels and so supply of oxygen to different organs and cells become slow and hence, respiration and release of energy becomes low, thereby making us feel lethargic. This disease is referred to as “anaemia”. Night blindness is a disease in which a person cannot see clearly in dim light due to defect in rod cells of retina. All these are genetic disorders. But, influenza is caused due to virus which is an external agent and hence, it is not a genetic disease. Thus, (1) (2) and (3) options are genetic diseases while (4) is not a genetic disorder.

Fever and cough last for a small duration and hence, they are acute. On the contrary, elephantiasis is a chronic disease, which lasts for a long time and makes the body and general health poor. In this disease, the person’s limbs, i.e. feet, legs, arms and hands, are highly swollen due to accumulation of water in the cells. The person looks bulky and his limbs are swollen. Hence, it is compared to elephant’s limbs and so the disease is termed “elephantiasis”. It should be noted that now small pox has been eradicated, but when it was prevalent, it used to last for a small time and cause death.