Health, Disease and Environment
Health, disease and environment mixes biology with environmental issues - disease transmission, immunity, ecosystems and conservation.
Human diseases
Infectious diseases spread through pathogens. Bacterial: tuberculosis (Mycobacterium), cholera, typhoid. Viral: influenza, polio, measles, AIDS (HIV), dengue. Protozoan: malaria (Plasmodium, spread by the female Anopheles mosquito). Worm: elephantiasis (Wuchereria). Non-infectious diseases include diabetes and cancer. Prevention relies on clean water, sanitation, vector control and vaccination.
Immunity
Innate immunity is present from birth and is non-specific; acquired immunity develops after infection or vaccination, is specific, and involves antibodies and memory cells. Vaccines contain weakened or killed pathogens or toxoids and stimulate antibody production, giving the body a head start.
Natural resources and ecosystem
Resources include soil, water, forests, coal and petroleum; fossil fuels are non-renewable. An ecosystem is a community plus its physical environment; producers, consumers and decomposers form food chains and webs. Only about 10% of the energy passes to the next trophic level, so food chains are short and top carnivores are few. Biogeochemical cycles (carbon, nitrogen, water) recycle matter.
Biodiversity and conservation
Biodiversity is the variety of species and habitats; India is a megadiverse country. Threats include deforestation, pollution, habitat loss, poaching and invasive species. Conservation uses protected areas - national parks, wildlife sanctuaries, biosphere reserves - plus afforestation, seed banks and laws.
Worked example
In the chain grass → grasshopper → frog → snake, if grass stores 10,000 kJ, the grasshopper receives about 1,000 kJ, the frog about 100 kJ and the snake about 10 kJ. That is why long chains cannot support large predators.
Traps
Saying malaria is caused by a virus; forgetting that the female mosquito transmits the parasite with the bite. Confusing a national park with a sanctuary.