26_nekton - Nekton GS222D.Lund Lecture26...

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Nekton GS222 – D. Lund Lecture 26
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Overview - this lecture Minimizing drag Fin adaptations – caudal fin aspect ratio Counter-shading and schooling Marine mammals
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Fish adaptations water is much harder to travel through than air fish shape is optimized for moving through water Must overcome 3 types of drag: Swimming 1) surface drag – friction between fish body and  water - increases as surface area increases - ideal shape would be a sphere, smallest  surface area to volume ratio why aren’t all fish ball shaped?
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Fish adaptations Other important types of drag: Swimming why aren’t all fish needle shaped? 2) form drag – force required to push water out of  the way - form drag is proportional to cross-sectional  area - ideal shape would be a needle
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Fish adaptations Other important types of drag: Swimming Fish compromise between these forms to minimize their drag. 3) turbulent drag – highly turbulent fluid flow will  imparts drag on an object - ideal form is one that is rounded in front  and tapered in the rear - promotes laminar (non-turbulent) flow
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Gymnosarda unicolor dogtooth tuna Clupea sp. herring
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Fin adaptations Like fins on an airplane, fins on a fish are essential for  controlling direction and stability Fin functions: 1) manuevering: pelvic and  pectoral fins, used to stop  and execute turns 2) stabilization: vertical  dorsal and anal fins 3) propulsion: caudal fin Fish alternatively contract and relax muscles on each side of body  to provide thrust, caudal fin provides final push
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Swimming by muscle contraction  and relaxation
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26_nekton - Nekton GS222D.Lund Lecture26...

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