Why Do We Fall Ill., Science, Class 9 - Test - Class 9 MCQ

The disease that affects our lungs is tuberculosis (TB).
Explanation:
- Tuberculosis is a bacterial infection caused by Mycobacterium tuberculosis that primarily affects the lungs but can also affect other parts of the body.
- It is an airborne disease that spreads through the air when an infected person coughs, sneezes, or speaks.
- TB primarily affects the lungs, causing symptoms such as persistent cough, chest pain, coughing up blood, fatigue, weight loss, and night sweats.
- If left untreated, TB can be life-threatening and can spread to other organs of the body, leading to complications.
- Diagnosis of TB involves various tests, including chest X-rays, sputum tests, and tuberculin skin tests.
- Treatment for TB usually involves a combination of antibiotics taken for several months to effectively kill the bacteria and prevent the development of drug-resistant strains.
- Prevention of TB includes vaccination with the Bacillus Calmette-Guérin (BCG) vaccine, which provides partial protection against severe forms of TB in children.
- Additionally, practicing good respiratory hygiene, such as covering the mouth and nose when coughing or sneezing, and avoiding close contact with individuals who have active TB can help prevent the spread of the disease.
In conclusion, tuberculosis is the disease that primarily affects our lungs. It is important to be aware of the symptoms, seek medical attention if necessary, and follow preventive measures to reduce the transmission of TB.

The BCG vaccine is given for the immunity against tuberculosis.

Explanation:

• The BCG vaccine is a vaccine that provides protection against tuberculosis (TB).


• Tuberculosis is a bacterial infection caused by Mycobacterium tuberculosis that primarily affects the lungs but can also affect other parts of the body.


• The BCG vaccine contains a weakened form of the bacteria that causes tuberculosis, called Mycobacterium bovis.


• When the BCG vaccine is given, it stimulates the immune system to produce a response that provides protection against tuberculosis.


• The BCG vaccine is primarily given to infants and children in countries where tuberculosis is common or where the risk of tuberculosis is high.


• It is not routinely given to adults in countries where tuberculosis is less common, as the vaccine is more effective at preventing severe forms of tuberculosis in children.


• However, in certain situations, adults may receive the BCG vaccine if they are at high risk of exposure to tuberculosis or if they have a weakened immune system.

Therefore, the correct answer is C: tuberculosis.

Malaria is caused by the Plasmodium parasite. The parasite can be spread to humans through the bites of infected mosquitoes. There are many different types of plasmodium parasite, but only 5 types cause malaria in humans.

Examples of Trypanosoma, Leishmania, and Plasmodium:
These are examples of protozoa. Protozoa are single-celled eukaryotic organisms that belong to the Kingdom Protista. They are microscopic and can be found in various environments, including water, soil, and inside the bodies of humans and animals.
Trypanosoma:

- Trypanosoma is a genus of parasitic protozoa that causes diseases such as sleeping sickness in humans and animals.
- Sleeping sickness is transmitted to humans through the bite of tsetse flies.
Leishmania:

- Leishmania is a genus of parasitic protozoa that causes leishmaniasis, a disease that affects the skin, mucous membranes, and internal organs.
- Leishmaniasis is transmitted to humans through the bite of infected sandflies.
Plasmodium:

- Plasmodium is a genus of parasitic protozoa that causes malaria, a life-threatening disease.
- Malaria is transmitted to humans through the bite of infected female Anopheles mosquitoes.
Key Points:
- Trypanosoma, Leishmania, and Plasmodium are examples of protozoa.
- Protozoa are single-celled eukaryotic organisms.
- Trypanosoma causes sleeping sickness, Leishmania causes leishmaniasis, and Plasmodium causes malaria.
- These diseases are transmitted to humans through the bites of infected vectors such as tsetse flies and mosquitoes.
- Protozoa can be found in various environments and can cause diseases in humans and animals.

Explanation:
The diseases diarrhoea, cholera, and typhoid have one thing in common, which is that they are all transmitted by contaminated food and water. Let us break down the answer into bullet points:
- All of them are caused by bacteria: This statement is incorrect. While cholera and typhoid are caused by bacteria (Vibrio cholerae and Salmonella typhi, respectively), diarrhoea can be caused by a variety of factors, including bacteria, viruses, or parasites.
- All of them are transmitted by contaminated food and water: This statement is correct. Diarrhoea, cholera, and typhoid are all primarily transmitted through the ingestion of contaminated food or water that contains the responsible bacteria or pathogens.
- All of them are cured by antibiotics: This statement is partially correct. While cholera and typhoid can be treated with antibiotics, not all cases of diarrhoea require antibiotic treatment. In fact, some cases of diarrhoea are caused by viral infections, which do not respond to antibiotics.
- All of the above (option D): This option is the correct answer because it includes the statement that all three diseases are transmitted by contaminated food and water, which is true.
In conclusion, the correct answer is D: All of the above. The diseases diarrhoea, cholera, and typhoid are all transmitted by contaminated food and water, although not all cases of diarrhoea are caused by bacteria, and not all cases of diarrhoea require antibiotic treatment.

The bacteria among the following is Salmonella typhi.
Explanation:
- Plasmodium is a protozoan parasite that causes malaria, not a bacteria.
- Trypanosoma is also a protozoan parasite that causes diseases like African sleeping sickness, not a bacteria.
- Rabies virus is a virus, not a bacteria.
- Salmonella typhi is a bacteria that causes typhoid fever.
In summary, among the given options, Salmonella typhi is the only bacteria.

Answer:
The HIV virus attacks the white blood cells in our body. Here is a detailed explanation:
Introduction:
HIV (Human Immunodeficiency Virus) is a virus that attacks the immune system, specifically the CD4 cells, which are a type of white blood cell that helps the body fight off infections. The virus weakens the immune system over time, making it difficult for the body to defend against infections and diseases.
The Role of White Blood Cells:
White blood cells, also known as leukocytes, are an essential part of the immune system. They are responsible for fighting off infections and diseases. There are different types of white blood cells, including lymphocytes, monocytes, neutrophils, eosinophils, and basophils. Lymphocytes, specifically T-lymphocytes (also called T-cells) and B-lymphocytes (also called B-cells), are the main targets of the HIV virus.
HIV and White Blood Cells:
Once the HIV virus enters the body, it attaches itself to the CD4 receptors on the surface of the white blood cells, particularly the CD4 T-cells. The virus then enters the cells and starts to replicate, causing damage to the immune system.
Impact on the Immune System:
As the HIV virus replicates within the white blood cells, it gradually destroys them. This leads to a decrease in the number of CD4 T-cells in the body, weakening the immune system's ability to fight off infections. Eventually, if left untreated, HIV can progress to AIDS (Acquired Immunodeficiency Syndrome), which is the final stage of the infection and is characterized by severe immune system damage.
Conclusion:
In summary, the HIV virus attacks and destroys the white blood cells, particularly the CD4 T-cells, which are vital for the proper functioning of the immune system. This weakening of the immune system leaves the body susceptible to various infections and diseases, ultimately leading to AIDS if not treated.

Pathogens of Disease
Pathogens are microscopic organisms or particles that can cause disease in humans and other organisms. The pathogens of disease include:
- Bacteria: Bacteria are single-celled microorganisms that can cause a wide range of infections, such as strep throat, urinary tract infections, and pneumonia. They can multiply rapidly and produce toxins that harm the body.
- Virus: Viruses are smaller than bacteria and cannot reproduce on their own. They invade host cells and use the host's cellular machinery to replicate. Common viral infections include the flu, common cold, and COVID-19.
- Protozoa: Protozoa are single-celled organisms that can cause diseases such as malaria, amoebic dysentery, and sleeping sickness. They can be transmitted through contaminated water or food, or through insect vectors like mosquitoes.
- All of the Above: All three categories of pathogens mentioned above - bacteria, viruses, and protozoa - can cause various diseases in humans and animals.
In conclusion, the pathogens of disease include bacteria, viruses, and protozoa. These microscopic organisms can cause a wide range of infections and illnesses, and it is important to understand their characteristics and methods of transmission in order to prevent and treat diseases effectively.

Penicillin is a drug that can:
- Interfere in the biological pathway of bacteria: Penicillin works by inhibiting the synthesis of the bacterial cell wall. It binds to and inhibits the enzyme responsible for cross-linking the peptidoglycan chains in the cell wall, which weakens the structure and leads to cell lysis.
- Act as an antibiotic that can kill bacteria: Penicillin is a type of antibiotic that is effective against a wide range of bacteria. It targets the bacterial cell wall, disrupting its structure and integrity, ultimately leading to the death of the bacteria.
- Both (a) and (b): Penicillin both interferes in the biological pathway of bacteria by inhibiting cell wall synthesis and acts as an antibiotic that can kill bacteria by weakening the cell wall and causing cell lysis.
- None of the above: This option is incorrect as both option A and B are true.
In conclusion, penicillin is a drug that can interfere in the biological pathway of bacteria by inhibiting cell wall synthesis and act as an antibiotic that can kill bacteria by weakening the cell wall and causing cell lysis. Therefore, the correct answer is option C: both (a) and (b).

Filariasis is a parasitic disease caused by an infection with roundworms of the Filarioidea type. These are spread by blood-feeding diptera such as black flies and mosquitoes. ... Lymphatic filariasis is caused by the worms Wuchereria bancrofti, Brugia malayi, and Brugia timori.