Biology and Human Welfare
Biology and Human Welfare covers pathogens, immunity, disease control, and the applied biology of plant and animal breeding.
Core rules
- Typhoid - Salmonella typhi; pneumonia - Streptococcus pneumoniae and Haemophilus influenzae; common cold - rhinoviruses; malaria - Plasmodium; amoebiasis - Entamoeba histolytica; ascariasis - Ascaris; filariasis - Wuchereria; ringworm - Microsporum, Trichophyton, Epidermophyton.
- Malaria: sporozoites from a female Anopheles bite → liver → merozoites → RBCs → haemozoin release causes chills and fever. Gametocytes are taken up by the next mosquito.
- Immunity: innate vs acquired; active (vaccine or infection) vs passive (antibodies transferred); primary and secondary responses; antibody = two heavy + two light chains; lymphoid organs.
- HIV: retrovirus, reverse transcriptase, helper T cells destroyed; ELISA screening. Cancer: proto-oncogenes → oncogenes, metastasis.
- Plant breeding: semi-dwarf wheat, Green Revolution, biofortification; apiculture, aquaculture, poultry.
Worked example
A patient has cyclic fever with chills and a blood smear showing ring-stage parasites inside RBCs. The blood stage explains the symptoms, but the liver stage must also be considered because it releases merozoites and because gametocytes are needed for mosquito transmission. Treating only the blood stage relieves illness but may not stop transmission.
Traps
Ringworm is a fungal infection, not a worm. Only female Anopheles transmits malaria. Passive immunity is short-lived because no memory cells form. Plasmodium vivax hypnozoites cause relapse.