Biology and Human Welfare
Domain 8 covers health, disease, microbes and food production. The exam tests pathogens, immunity, vaccines, antibiotics, microbial products, biofertilisers and fermentation.
Core rules
- Pathogens include bacteria, viruses, protozoa, fungi and helminths. Malaria is caused by Plasmodium and transmitted by female Anopheles; dengue is viral and transmitted by Aedes.
- Immunity: innate barriers and phagocytes; adaptive immunity uses B cells (antibodies) and T cells. Colostrum contains IgA.
- Vaccines expose the immune system to antigens, creating memory cells. Antibiotics target bacterial structures but do not work on viruses.
- Microbes produce antibiotics, enzymes, organic acids and alcohol. Fermentation by yeast converts sugar to ethanol and CO2.
- Biofertilisers include Rhizobium (symbiotic nitrogen fixation), Azotobacter (free-living) and mycorrhizae (phosphorus uptake).
Worked example
A patient has fever with chills and a blood smear shows ring-shaped parasites in red blood cells. Identify the disease and vector. The parasite is Plasmodium, so the disease is malaria; the vector is the female Anopheles mosquito. Reasoning: Plasmodium invades RBCs and causes cyclical fever; male mosquitoes do not bite, so the vector is female. Antibiotics would not treat a protozoan infection; antimalarial drugs are used.
Traps
- Saying antibiotics cure viral colds; they do not.
- Confusing Rhizobium with free-living Azotobacter; Rhizobium is symbiotic.
- Claiming colostrum provides IgG; it is rich in IgA.
- Mixing malaria vector with dengue vector; Anopheles vs Aedes.