Biology, food and health

A wasp doesn't spray a single drop of chemical. Released near a walnut orchard, it alone destroys the aphids eating the crop.

Plant and animal breeders use genetics to create better wheat, rice, corn, chicken, cows and sheep. Poultry breeders have even developed broilers for quick, cheap white meat.

Genetic engineering inserts genes for disease resistance into plants, creating transgenic plants with foreign DNA. These plants are then multiplied by cloning, using techniques like tissue culture.

Chemical pesticides once controlled crop-damaging fungi and insects, but they poison people, pollute the environment, and let pests evolve resistance. Biological control avoids this by using living organisms that compete with or eat the pests instead.

A wasp that parasitizes the aphid attacking walnut trees is one such example; even some bacteria now serve as bio-pesticides. Using every suitable method against a pest or disease together is called integrated disease management.

Since soil makes nutrient experiments difficult, hydroponic culture grows plants in aerated, nutrient-rich water instead — a technique astronauts may one day use. Pasteurization, developed by Louis Pasteur, preserves milk from spoilage during storage and transport.

Disease control itself follows three prongs. Preventive measures come first: knowing that HIV spreads through sexual contact, blood transfusion and contaminated syringes lets people avoid those exact risks, since AIDS still has no cure.

Edward Jenner developed vaccination in 1796 using cowpox pus, called vacca in Latin — the origin of "vaccine". Vaccination now controls polio, whooping cough, measles and mumps, and has eliminated smallpox worldwide.

Antibiotics treat bacterial disease, unless the bacteria have grown resistant. Cancer is treated with radiotherapy or chemotherapy, though chemotherapy's chemicals can kill healthy cells too. Gene therapy instead repairs a defective gene by inserting a normal copy through bone marrow cells.