Nares, nasal cavity, pharynx, larynx, trachea, bronchus, bronchioles, alveoli
I travel to the countryside to breathe in the fresh open air. Alternatively I could have said "I travel to the countryside to breathe in and breathe out the air in order to refresh myself".
The dragonfly nymphs actually come to the surface of the water in order to breathe. They have gills at the base of their rectum and breathe through their bottom.
Although precise mechanisms of travel might be origin specific, in general, cancer cells travel through invasion and migration. In order to metastatsize to other organs the cells invade through the tissues in your body and move by mechanisms that promotes cellular migration, often by reorganizing actin networks. They are often aided by the physical movement of lymph through tissues or by entering blood vessels and travelling via blood circulation.
What_is_the_process_of_a_nervous_impulse_traveling_through_a_neuron
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You need oxygen in your lungs in order to breathe. Without blood to transport it your lungs would have none and you wouldn't be able to breathe.
Yes, mechanical waves do need a medium in order to travel. Other waves, such as light, do not (thus they can travel through space).
nostril,pharynx and bronchi
Cylindrical
Animals need a lot of energy to move or travel to places.
Spongy materials are the most difficult for sound to travel through. Vacuum is the best acoustic insulation but it doesn't really count for the purpose of this question, since it is not a material but a lack of material.
longitudinal waves definitely requires a medium(air,water,solid) in order to transmit it does not travel through vaccum