NUMS — Medical & Dental Entry Test

NUMS Biology — Biodiversity: Viruses, Bacteria and Kingdoms (Set 2)

Take the NUMS Biology — Biodiversity: Viruses, Bacteria and Kingdoms (Set 2): 30 multiple-choice questions (40 minutes) with instant scoring and a full…

What this test covers

30 NUMS Biology

Sample questions with answers

The first 5 questions of this test, with the correct answer and explanation.

Q1. A scientist names a newly found plant 'Mangifera indica'. In this binomial name, 'indica' is the:
- A. Genus name
- B. Order name
- C. Family name
- D. Specific epithet ✓
Answer: D. Specific epithet
Explanation: In binomial nomenclature the first word (capitalised) is the genus and the second (lower case) is the specific epithet; together they name the species.
Q2. Which rank contains the greatest number of organisms sharing the fewest common characteristics?
- A. Genus
- B. Family
- C. Kingdom ✓
- D. Species
Answer: C. Kingdom
Explanation: Higher ranks are broader: a kingdom includes many phyla and therefore the most diverse organisms.
Q3. Carl Woese's three-domain system separated prokaryotes into Bacteria and Archaea mainly on the basis of differences in:
- A. Cell shape
- B. Mode of nutrition
- C. Ribosomal RNA sequences and membrane lipids ✓
- D. Presence of flagella
Answer: C. Ribosomal RNA sequences and membrane lipids
Explanation: Comparison of 16S rRNA sequences and unique ether-linked membrane lipids showed Archaea are as distinct from Bacteria as from eukaryotes.
Q4. Two organisms are placed in the same genus. Which pair of ranks must they also share?
- A. Family and order ✓
- B. Only kingdom
- C. Species and family
- D. Species and order
Answer: A. Family and order
Explanation: Each genus belongs to one family, which belongs to one order; so members of one genus share all higher ranks, but not necessarily the species.
Q5. A student argues that viruses should be treated as cells. Which fact best counters this argument?
- A. They have 70S ribosomes
- B. They divide by binary fission
- C. They can make ATP independently
- D. They contain either DNA or RNA but not both ✓
Answer: D. They contain either DNA or RNA but not both
Explanation: A virion has a single type of nucleic acid in a protein coat and relies on host ribosomes and energy for replication.

The other 25 questions

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Q6. Tobacco mosaic virus has a helical capsid, while adenovirus has an icosahedral capsid. The capsid in each case is built from repeating protein units called:
- A. Peplomers
- B. Prophages
- C. Capsomeres
- D. Nucleoids
Q7. Influenza virus changes its surface haemagglutinin slightly every few years, so a new vaccine is needed. This is mainly because:
- A. It is a bacterium that becomes resistant
- B. Vaccines destroy the host's memory cells
- C. Its RNA genome mutates frequently and RNA replication lacks proofreading
- D. It has no nucleic acid
Q8. The first virus to be crystallised, showing that viruses can behave like chemical substances outside cells, was:
- A. Tobacco mosaic virus (by Stanley)
- B. Bacteriophage T4 (by Twort)
- C. Smallpox virus (by Jenner)
- D. Polio virus (by Salk)
Q9. AZT, a drug used against HIV, is a nucleoside analogue that blocks the viral enzyme which copies RNA into DNA. This enzyme is:
- A. DNA ligase
- B. Restriction endonuclease
- C. Reverse transcriptase
- D. RNA polymerase II
Q10. HIV enters helper T cells because its envelope glycoprotein gp120 binds to the host-cell surface molecule:
- A. Acetylcholine receptor
- B. CD4
- C. Insulin receptor
- D. Haemoglobin
Q11. In the lytic cycle of phage T4, the step immediately after synthesis of phage DNA and proteins inside the bacterium is:
- A. Attachment to the cell wall
- B. Assembly of new phage particles
- C. Integration into the bacterial chromosome
- D. Injection of DNA
Q12. Polio virus mainly damages which cells, which can lead to paralysis?
- A. Cells of the alveoli
- B. Red blood cells
- C. Motor neurons of the spinal cord
- D. Liver cells
Q13. Which disease is caused by a virus spread through Aedes mosquito bites?
- A. Malaria
- B. Cholera
- C. Dengue fever
- D. Typhoid
Q14. A rod-shaped bacterium is described as a 'bacillus', while a comma-shaped one is a:
- A. Coccus
- B. Spirillum
- C. Streptococcus
- D. Vibrio
Q15. Gram-negative bacteria lose the crystal violet during the alcohol wash in the Gram stain. This is because:
- A. Their peptidoglycan layer is very thick
- B. They lack a cell wall entirely
- C. Their thin peptidoglycan layer and lipid-rich outer membrane do not retain the dye complex
- D. They have no cell membrane
Q16. The bacterial cell wall is made mainly of:
- A. Cellulose
- B. Pectin
- C. Chitin
- D. Peptidoglycan (murein)
Q17. Bacteria reproduce asexually mainly by:
- A. Meiosis
- B. Mitosis
- C. Spore fusion
- D. Binary fission
Q18. A bacterial population starts with 500 cells and doubles every 30 minutes. How many cells are present after 3 hours (assuming no deaths)?
- A. 16 000
- B. 3 000
- C. 64 000
- D. 32 000
Q19. In a closed culture, the phase in which the number of new cells equals the number of dying cells is the:
- A. Lag phase
- B. Decline phase
- C. Stationary phase
- D. Log phase
Q20. A virus carries a gene from one bacterium to another, giving the second bacterium a new trait. This process is:
- A. Transduction
- B. Transformation
- C. Binary fission
- D. Conjugation
Q21. Genes for antibiotic resistance often spread quickly between different bacterial species in a hospital. The structures most often carrying these genes are:
- A. Capsules
- B. Endospores
- C. Mesosomes
- D. Plasmids
Q22. Bacteria such as Nitrosomonas obtain energy by oxidising ammonia and use it to fix CO₂. They are described as:
- A. Chemoautotrophs
- B. Saprotrophs
- C. Photoautotrophs
- D. Parasites
Q23. Which bacterium is used to convert milk into yoghurt?
- A. Lactobacillus
- B. Rhizobium
- C. Salmonella
- D. Clostridium
Q24. Leguminous plants grown in nitrogen-poor soil still produce protein-rich seeds. This is due to:
- A. Nitrifying bacteria converting nitrate to N₂
- B. Rhizobium in root nodules fixing atmospheric N₂ into ammonia
- C. Denitrifying bacteria adding nitrates
- D. Fungi in the roots fixing CO₂
Q25. Plasmodium, the cause of malaria, belongs to the group of protozoa that:
- A. Move using flagella
- B. Move using cilia
- C. Move by pseudopodia
- D. Are non-motile parasites forming spores (sporozoans)
Q26. Diatoms, which form a large part of marine phytoplankton, are notable for:
- A. Cell walls made of chitin
- B. Lacking chlorophyll
- C. Moving by pseudopodia
- D. Cell walls (frustules) made of silica
Q27. The cell walls of fungi are made mainly of chitin, and their storage carbohydrate is:
- A. Cellulose
- B. Glycogen
- C. Sucrose
- D. Starch
Q28. Penicillium is used commercially to produce penicillin. Which feature of fungi makes them suitable for large-scale fermentation?
- A. Ability to photosynthesise
- B. Their need for living host tissue
- C. Rapid growth on cheap organic media and release of products into the medium
- D. Cell walls made of cellulose
Q29. Yeast used in baking is a unicellular fungus that reproduces asexually mainly by:
- A. Conjugation
- B. Budding
- C. Fragmentation of hyphae only
- D. Binary fission
Q30. Viroids, which cause diseases such as potato spindle tuber disease, consist of:
- A. Short circular RNA without a protein coat
- B. Protein only
- C. DNA enclosed in a lipid envelope
- D. RNA with a protein capsid