Humans are ureotelic—they excrete nitrogenous waste mainly as urea, which is less toxic than ammonia and requires moderate water for excretion. Ammonia is excreted by aquatic animals, uric acid by birds and reptiles (to conserve water), and creatinine is also excreted but is a minor component compared to urea.
Explanation:
Sericulture is the process of rearing silkworms (primarily Bombyx mori) for the production of silk. The silkworm feeds on mulberry leaves (Morus alba) and spins a continuous filament of silk protein (fibroin) to form a cocoon around itself during its pupal stage. The cocoons are then boiled to kill the pupa and unwind the silk filament for textile production.
Explanation:
Auxin (indole-3-acetic acid) produced at the shoot apex suppresses the growth of lateral buds, a phenomenon called apical dominance. Removing the apex allows lateral buds to grow. Cytokinin promotes cell division and counteracts apical dominance. Gibberellin stimulates stem elongation, and ethylene is involved in fruit ripening and senescence. The auxin-cytokinin ratio determines root and shoot differentiation in tissue culture.
Explanation:
Alexander Fleming, a Scottish bacteriologist, discovered penicillin in 1928. He returned from a vacation to find that a Petri dish containing Staphylococcus bacteria had been accidentally contaminated by a mold. He noticed a clear zone around the mold where the bacteria had been killed. The mold was identified as Penicillium notatum, and the antibacterial substance was named penicillin.
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