Microbiology and Disease Quiz

Grade 9 · Science · Quiz

Challenge yourself on pathogens, the immune system, disease transmission, and modern microbiology concepts.

Questions

  1. Which type of pathogen is responsible for malaria?

    1. Bacterium
    2. Virus
    3. Protozoan
    4. Fungus
    Show answer

    Answer: Protozoan

    Malaria is caused by Plasmodium species, which are protozoa (unicellular eukaryotes). They are transmitted by the Anopheles mosquito and infect and destroy red blood cells.

  2. A student has a bacterial infection and is prescribed antibiotics. After 3 days she feels better and stops taking them. What is the primary risk of this action?

    1. The remaining bacteria that survived are likely the more resistant ones and may multiply
    2. Her immune system will become dependent on antibiotics
    3. The antibiotics will lose effectiveness in the pill bottle
    4. She will develop a viral infection to replace the bacterial one
    Show answer

    Answer: The remaining bacteria that survived are likely the more resistant ones and may multiply

    When a patient stops antibiotics early, the bacteria that were killed first are the most susceptible. The remaining bacteria are those more resistant to the antibiotic. These survive, reproduce, and can spread, leading to resistant strains.

  3. HIV targets and destroys which type of immune cell, making infected individuals vulnerable to opportunistic infections?

    1. B cells
    2. Red blood cells
    3. CD4+ T helper cells
    4. Neutrophils
    Show answer

    Answer: CD4+ T helper cells

    HIV specifically infects CD4+ T helper cells (T lymphocytes). These cells coordinate the entire adaptive immune response. Destroying them progressively cripples immunity, leading to AIDS and vulnerability to opportunistic infections.

  4. Which of the following is an example of passive immunity?

    1. Recovering from chickenpox and gaining lifelong immunity
    2. Receiving the MMR vaccine
    3. A newborn receiving antibodies through breast milk
    4. T cells destroying virus-infected cells
    Show answer

    Answer: A newborn receiving antibodies through breast milk

    Passive immunity involves receiving pre-made antibodies from another source — no immune memory is formed. A newborn receiving maternal antibodies through breast milk is a natural example. Active immunity requires the immune system to generate its own response.

  5. What is the difference between lytic and lysogenic viral replication cycles?

    1. Lytic destroys the host cell immediately; lysogenic integrates DNA and delays destruction
    2. Lytic integrates into the genome; lysogenic destroys the cell immediately
    3. Both cycles immediately destroy the host cell
    4. Lysogenic produces more virus particles than lytic
    Show answer

    Answer: Lytic destroys the host cell immediately; lysogenic integrates DNA and delays destruction

    In the lytic cycle, the virus immediately replicates inside the host cell, bursting (lysing) it to release new virions. In the lysogenic cycle, viral DNA integrates into the host genome (as a prophage) and is replicated with it, potentially activating later.

  6. Herd immunity is achieved when:

    1. Every single person in a community is vaccinated
    2. A sufficient proportion of a population is immune, reducing pathogen spread and protecting the unvaccinated
    3. Antibiotics are distributed to an entire community
    4. A pathogen mutates to become less virulent over time
    Show answer

    Answer: A sufficient proportion of a population is immune, reducing pathogen spread and protecting the unvaccinated

    Herd immunity (community immunity) is when enough of a population is immune that a pathogen cannot easily spread, even to those who are not immune. The threshold varies by pathogen (e.g., ~95% for measles).

  7. All bacteria are harmful to humans and cause disease.

    Show answer

    Answer: False

    The vast majority of bacteria are harmless or beneficial. The human gut microbiome contains trillions of beneficial bacteria that aid digestion, produce vitamins (K and B12), and help train the immune system. Only a small fraction of bacterial species are pathogenic.

  8. The branch of medicine that studies the distribution and determinants of diseases in populations is called ___.

    Show answer

    Answer: epidemiology

    Epidemiology is the study of how diseases spread, their frequency, and the factors that influence their distribution in populations. It is the foundation of public health and disease control strategies.

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