How Sharks Use Diffusion

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You must have observed in experiments related to diffusion that if you drop ink in water it takes quite a while to dissipate , so how can the individual particles of smell travel so far and quickly? Apparently a shark can smell the blood of their prey up to a quarter of a mile away.There is two ways that sharks receive the scent of blood, diffusion and water currents. Diffusion is an extremely slow process as you have observed in the ink experiment. The molecules that carry the odour of the blood gradually disperse from its starting point, from where the concentration gradient is highest, moving randomly and slowly across the water until the shark catches its scent. The other way is when the water currents carry the blood molecules by the movement of water. This method is faster for the scent to travel quickly towards the shark. The travel time of odour depends entirely on the local water velocity. The scent of blood could reach the shark in just a few minute depending on how fast the water is moving and how far the shark is. The hunting shark will swim in spirals, thereby eliminating the currents that don't carry the scent of blood and following those that do. Diffusion not only happens in liquids but takes place in gases too. It helps Predators like tigers to detect their prey. Scent molecules of the prey spread gradually from the highly concentrated source moving randomly and quickly in the surrounding air where there is low concentration .these scent molecules travel faster than those in water because of the surrounding air (gas). Gas particles are further apart from each other than those in water so this helps them move more freely in a quicker time. If the wind velocity is higher then the particles would travel quicker until the tiger detects

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