Biology and Human Welfare
Biology and Human Welfare links pathogens, immunity, animal husbandry and plant breeding to real outcomes: disease control, food security and drug safety. Board questions are often "why" questions - why a booster dose works, why the Green Revolution needed semidwarf wheat.
Pathogens and disease
- Malaria: Plasmodium vivax and P. falciparum (most severe), transmitted by the female Anopheles; sporozoites go to liver then red blood cells, and haemozoin release causes chill and fever.
- Amoebiasis (Entamoeba histolytica), ascariasis (Ascaris), filariasis (Wuchereria), ringworm (Microsporum, Trichophyton, Epidermophyton - fungi, not worms).
Immunity
- Innate: barriers, phagocytes, natural killer cells. Acquired: B and T lymphocytes with memory.
- Active immunity: own antibodies after infection or vaccination. Passive immunity: ready-made antibodies from colostrum or antivenom.
- The primary response is slow and small; the secondary response is faster and larger because memory cells are pre-armed.
Breeding and biofortification
- Green Revolution: semidwarf, fertiliser-responsive wheat (Kalyan Sona, Sonalika) and rice (IR-8).
- Biofortification: Atlas 66 wheat (protein), iron-fortified rice, beta-carotene-rich carrot and golden rice.
- Somatic hybridisation (pomato), meristem culture for virus-free plants, micropropagation for rapid clonal multiplication.
Worked example
A child's antibody titre peaks at about 10 units on day 12 after dose 1, then falls. After dose 2 the titre peaks at about 100 units within 5 days. Reasoning: dose 1 activates naive B cells, so clonal selection and class switching are slow; dose 2 meets memory B cells, so the lag is shorter, the peak higher and IgG replaces IgM.
Traps that cost marks
- Swapping active and passive immunity.
- Saying the male mosquito transmits malaria; only the female bites.
- Writing that colostrum gives active immunity.