Adaptations for Gas Exchange
- Created by: Emily Cartwright
- Created on: 27-05-14 17:23
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- Adaptations for Gas Exchange
- All living organisms need to exchange gases with their environment
- Gas exchange occurs by diffusion
- Gas exchange is 'The diffusion of gases into and out of cells so respiration can take place'
- Gas exchange occurs by diffusion
- Although living organisms have become adapted for gas exchange in different ways, all gas exchange surfaces share the following properties
- Permeable to gases
- Moist, because gases must dissolve before they can diffuse across membranes
- Large surface area
- Thin, to provide a short diffusion pathway
- Large, active animals can also have ventilating mechanisms to maintain steep concentration gradients across the gas exchange surface
- Surface area: Volume Ratio
- Volume is proportional to the demand for oxygen
- Demand will increase with an increase in metabolic rate (as an organism increases in size
- As the cell increases in size, eventually simple diffusion will no longer satisfy demand for oxygen
- Demand will increase with an increase in metabolic rate (as an organism increases in size
- The smaller an animal, the larger the SA:V ratio
- The larger an animal, the smaller it's SA:V ratio
- Volume is proportional to the demand for oxygen
- Unicellular Organisms
- Amoeba
- Small, unicellular organism
- Has a large SA:V ratio
- It it unicellular (thin) so the diffusion pathway is short
- It also lives in water, so the entire surface area of the amoeba is moist
- Diffusion of gases occurs across the whole surface membrane
- The amoeba is unicellular, so the rate of uptake of oxygen is fast enough to satisfy the demands of oxygen by the organism
- Amoeba
- Multicellular Organisms
- As an organism gets larger, the demand for oxygen increases, but SA:V ratio decreases
- Diffusion pathways also become longer
- Their demand for oxygen can no longer be met by simple diffusion through their surface skin
- All living organisms need to exchange gases with their environment
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