CDS Biology · Free notes
Microbiology and Disease: CDS Biology
Microbiology and Disease has 18 past-year questions in CDS General Knowledge, from 2016 (II) to 2026 (II): 7 EASY, 9 MODERATE and 2 HARD. Most of them name a disease and ask what causes it or how it spreads, so a short list of diseases under bacteria, viruses, fungi, protozoa and worms answers many of them. Both HARD questions are about the AYUSH systems, which are not in any science textbook, so learn the cities of the national institutes from the table. Keep the protozoan pairs and the three mosquitoes apart, since the options are built from them.
The handout has every subtopic, worked example, formula and trap with answers shown. The formula sheet is the chapter’s formulas and traps alone, on one page.
Subtopic notes
Pathogens and Their Spread
12 PYQsWhich diseases are caused by bacteria, viruses, fungi, protozoa and worms, what makes viruses different, how diseases spread from one person to another, and what endemic, epidemic and pandemic mean.
Vaccines, Antibiotics and AYUSH
6 PYQsWho gave medicine the vaccine and the antibiotic, how penicillin kills bacteria and why antibiotics do nothing to a virus, and the AYUSH systems with their national institutes.
Formula & revision sheet
0 formulas · 7 reference tables · 12 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
0 formulas · 7 reference tables · 12 gotchas across all subtopics — the exam-eve cheat-sheet
Reference tables (4)
Diseases by kind of pathogen9 rows
| Disease | Pathogen | Kind |
|---|---|---|
| Tuberculosis | Mycobacterium tuberculosis | Bacterium |
| Peptic ulcer | Helicobacter pylori | BacteriumQ CDS 2020 (II): besides excess acid, peptic ulcers are caused by Helicobacter pylori. |
| Typhoid | Salmonella typhi | Bacterium |
| Dengue | Dengue virus | Virus |
| Athlete's foot, ringworm | Fungi | Fungus |
| Malaria | Plasmodium | Protozoan |
| Sleeping sickness | Trypanosoma | ProtozoanQ Asked twice: CDS 2019 (II) and 2021 (I). Leishmania causes kala-azar, not sleeping sickness. |
| Kala-azar | Leishmania | Protozoan |
| Elephantiasis | Wuchereria | Worm |
Viruses6 rows
| Virus | Genetic material | Fact to remember |
|---|---|---|
| HIV | RNA | Destroys helper T lymphocytes; causes AIDS |
| Dengue virus | RNA | A flavivirus spread by the Aedes mosquitoQ CDS 2024 (I): dengue virus is a flavivirus, an RNA virus; the right option was printed as 'Flavi-ribo virus'. |
| Influenza virus | RNA | Changes fast, so the vaccine is updated |
| Polio virus | RNA | Prevented by oral and injected vaccines |
| Hepatitis B virus | DNA | Spread through blood |
| Adenovirus | DNA | Causes colds and eye infections |
How diseases spread7 rows
| Route | Examples |
|---|---|
| Air (droplets from coughs and sneezes) | Tuberculosis, common cold, influenzaQ CDS 2018 (I): crowded places raise the risk of tuberculosis because its bacteria spread in droplets; Statement II explains Statement I. |
| Water and food | Cholera, typhoid, hepatitis A |
| Female Anopheles mosquito | MalariaQ CDS 2026 (II): only female Anopheles take human blood, and Plasmodium can cross the placenta; both statements are correct. |
| Aedes mosquito | Dengue, chikungunya |
| Culex mosquito | Filariasis (elephantiasis) |
| Tsetse fly | Sleeping sickness |
| Sexual contact and blood | AIDS, hepatitis B, syphilis |
Endemic, epidemic and pandemic5 rows
| Term | Meaning | Example |
|---|---|---|
| Endemic | Steady level in one area | Malaria in parts of India |
| Epidemic | Sudden rise above the usual level | A cholera outbreak after a flood |
| Pandemic | Epidemic across continents | COVID-19 |
| Sporadic | Scattered, occasional cases | A few tetanus cases |
| Chronic, endemic disease | Slow, long-lasting, no sudden outbreaks | ElephantiasisQ CDS 2020 (I): of cholera, malaria, smallpox and elephantiasis, elephantiasis is not an epidemic disease. |
Watch out for (7)
- Trypanosoma and Leishmania→ Diseases by kind of pathogen
- Ulcers are not only from acid→ Diseases by kind of pathogen
- HIV attacks lymphocytes, not red cells or platelets→ Viruses
- Why RNA viruses change fast→ Viruses
- Three mosquitoes, three diseases→ How diseases spread
- Visiting crowds is a risk, not a cause→ How diseases spread
- Endemic is steady, epidemic is a spike→ Endemic, epidemic and pandemic
Reference tables (3)
Vaccines and the scientists behind them5 rows
| Scientist | Contribution |
|---|---|
| Edward Jenner | Smallpox vaccine (1796); immunisationQ CDS 2020 (I): Edward Jenner introduced immunisation to medicine. |
| Louis Pasteur | Rabies and anthrax vaccines; pasteurisation |
| Robert Koch | Bacteria of tuberculosis and cholera |
| Alexander Fleming | Penicillin (1928) |
| Robert Hooke | Saw and named the cell (1665) |
How antibiotics work5 rows
| Question | Answer |
|---|---|
| Who discovered penicillin? | Alexander Fleming, 1928, from the mould Penicillium |
| What does penicillin block? | Building of the bacterial cell wall |
| Why is penicillin safe for us? | Human cells have no cell wall |
| Why does an antibiotic not cure a viral disease? | A virus has no pathways of its own for the antibiotic to blockQ CDS 2021 (I): a virus does not use pathways an antibiotic can block, but a vaccine boosts immunity against it. |
| What happens when antibiotics are overused? | Bacteria become resistant |
AYUSH systems of medicine7 rows
| System | National institute |
|---|---|
| Ayurveda | National Institute of Ayurveda, JaipurQ CDS 2019 (II): Ayurveda Jaipur, Homoeopathy Kolkata, Unani Bengaluru, Siddha Chennai. |
| Homoeopathy | National Institute of Homoeopathy, Kolkata |
| Unani | National Institute of Unani Medicine, BengaluruQ CDS 2024 (II): the false statement is that Unani has been dissociated from the Ministry of Ayush; it is still one of its systems. |
| Siddha | National Institute of Siddha, Chennai |
| Sowa-Rigpa | National Institute of Sowa Rigpa, Leh |
| Yoga | Morarji Desai National Institute of Yoga, New Delhi |
| Naturopathy | National Institute of Naturopathy, Pune |
Watch out for (5)
- Jenner for vaccines, Koch for germs→ Vaccines and the scientists behind them
- Penicillin blocks the wall, not DNA or RNA→ How antibiotics work
- Antibiotics fail on viruses for a reason of pathways→ How antibiotics work
- Sowa-Rigpa is in AYUSH, Reiki is not→ AYUSH systems of medicine
- Jaipur and Kolkata, Bengaluru and Chennai→ AYUSH systems of medicine
PYQ weightage by concept
7 concepts · 18 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
7 concepts · 18 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Diseases by kind of pathogen | 4 | 22% |
| Viruses | 3 | 17% |
| How diseases spread | 3 | 17% |
| Endemic, epidemic and pandemic | 2 | 11% |
| Concept | PYQs | Share |
|---|---|---|
| AYUSH systems of medicine | 3 | 17% |
| How antibiotics work | 2 | 11% |
| Vaccines and the scientists behind them | 1 | 6% |
Test yourself on a real paper
Sit a past CDS paper, timed and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.