Scoliodon is a cartilaginous fish (Chondrichthyes), possessing a cartilaginous endoskeleton, placoid scales, and ventral mouth. Rohu and Catla are bony fishes (Osteichthyes). Hippocampus is also a bony fish. Chondrichthyes include sharks, rays, and skates. They lack an air bladder and have to swim constantly to avoid sinking.
Explanation:
Nitrogen fixation is the conversion of inert atmospheric N₂ into ammonia (NH₃) by free-living (e.g., Azotobacter) or symbiotic (e.g., Rhizobium) bacteria, or by industrial processes. Nitrification is the oxidation of ammonia to nitrites then nitrates. Denitrification converts nitrates to N₂ gas. Ammonification is the release of ammonia from organic nitrogen by decomposers. Fixed nitrogen is essential for plant growth.
Explanation:
Acetobacter aceti and related species oxidize ethanol to acetic acid (vinegar) in the presence of oxygen. This is an aerobic fermentation process. Lactobacillus produces lactic acid, Pseudomonas can spoil food, Bacillus includes various industrial strains. Vinegar is used as a condiment and preservative.
Explanation:
Alexander Fleming noticed in 1928 that a mold contaminant (Penicillium notatum) on a bacterial culture plate inhibited the growth of Staphylococcus aureus, leading to the discovery of penicillin, the first widely used antibiotic. Florey and Chain later purified it. Pasteur developed pasteurization.
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