Health, Disease and Applied Biology
What this domain tests
Pathogens and transmission, the body's defences, immunity and vaccination, common diseases (malaria, TB, HIV/AIDS, cholera), and applied biology such as food preservation and biotechnology.
Core rules
- Pathogens include bacteria, viruses, protoctists and fungi; viruses cannot be killed by antibiotics because they are not living cells.
- Barriers (skin, mucus, stomach acid) are the first line; phagocytes and antibodies form the second.
- Active immunity follows infection or vaccination and involves antibody production; passive immunity is short-lived and comes from ready-made antibodies, including across the placenta.
- Malaria is caused by Plasmodium and transmitted by the bite of a female Anopheles mosquito; the mosquito is a vector, not the pathogen.
- Food preservation works by slowing or stopping microbial growth: drying, salting, canning, refrigeration.
Worked example
Reported malaria cases in a district fall from 1 200 to 300 in one year. The reduction is 900 cases. Percentage reduction = 900 ÷ 1 200 × 100 = 75%. Always divide the change by the original value, not the new one, and state both the change and the percentage.
Traps that cost marks
- Prescribing antibiotics for a viral infection such as influenza.
- Writing that HIV is spread by mosquitoes or by sharing food.
- Confusing antigen (the marker on a pathogen) with antibody (the protein produced against it).
- Describing passive immunity as long-lasting.