SA:Vol 0.0 / 5 ? BiologyBiological moleculesASAQA Created by: HindleycCreated on: 01-06-18 10:55 What does an organisms requirement to obtain materials depend on? Its metabolic rate 1 of 16 What does metabolic activity increase with? Volume 2 of 16 What does the rate of exchange of substances and heat depend on? The organisms SA 3 of 16 What substances must all organisms exchange with their surroundings? Food, waste, gases and heat 4 of 16 What must these substances do? Diffuse between the organisms and the surroundings 5 of 16 What is the rate at which a substance can diffuse given by? Ficks law- SAxConc difference / distance 6 of 16 What does the ability to meet the requirements depend on? The surface area: volume ratio 7 of 16 What happens as an organism gets bigger? SA:vol decreases as volume increases more than SA 8 of 16 What happens with a small SA and relatively large volume? Rate of diffusion and heat exchange low so difficult to exchange substances with their surroundings 9 of 16 What adaptations increase SA? Folding/branching, Longer/thiner/flat, 10 of 16 What other adaptations to inc rate? Maintain high conc gradient and minimise distance over which exchange occurs 11 of 16 What does a small SA:Vol ratio mean? Lose less heat than small animals 12 of 16 What do large mammals do? Keep warm quite easily and don't need much insulation or heat generation 13 of 16 What do small mammals and birds do? Lose heat very readily so need high metabolic rate in order to keep generating heat along with thick insulation- feed continuously 14 of 16 When you lose heat quickly to the surroundings you.. Have to respire quickly to generate heat to replace what is lost. 15 of 16 What must they do then? Consume more food and oxygen per unit of body weight than larger animals (high H.R) 16 of 16
WHY MULTICELLULAR ORGANISMS NEED SPECIALISED EXCHANGE SURFACES AND SINGLE CELLED ORGANISMS DO NOT 4.5 / 5 based on 3 ratings
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