tailieunhanh - Báo cáo sinh học: "Hitching a lift hydrodynamically - in swimming, flying and cycling"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Hitching a lift hydrodynamically - in swimming, flying and cycling. | J. Biol. Journal of Biology BioMed Central Minireview Hitching a lift hydrodynamically - in swimming flying and cycling R McNeill Alexander Address School of Biology University of Leeds Leeds LS2 9JT UK. E-mail Published 4 May 2004 Journal of Biology 2004 3 7 The electronic version of this article is the complete one and can be found online at http content 3 2 7 2004 BioMed Central Ltd Abstract Swimming animals set the water around them moving and flying animals generate air movements. Other animals traveling with them can save energy by exploiting these movements of the fluid medium similarly a cyclist can save energy by riding close behind another. A new study of dolphin mothers and calves exemplifies the advantages of moving in concert. Animals set the fluid around them moving when they swim through water or fly through air. In some circumstances one animal can take advantage of the fluid movements generated by another to reduce the energy cost of its locomotion. A possible example of an animal benefiting from this principle is a dolphin calf swimming with its mother. The animals swim side by side laterally separated by 1-2 calf diameters with the calf beside the rear half of the mother s body Figure 1a . Weihs 1 has now analyzed the hydrodynamics of the interaction between them. As a mother dolphin glides passively forward water is pushed out in front of her and drawn in behind her Figure 1b . These water movements could assist the swimming of an accompanying calf. When the mother swims by beating her tail fluke up and down she drives a jet of water backwards Figure 1c . This jet would impede the swimming of a calf immediately behind her but a calf in the position shown in Figure 1a would be swimming in forward-moving water and so would to some extent get a free ride. The water around it would also be moving obliquely inwards towards the mother tending to keep the calf close to her. In contrast a calf swimming beside the .

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