Adaptations for Gas Exchange
- Created by: Emily Cartwright
- Created on: 14-04-14 21:07
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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: 'The diffusion of gases into and out of cells so respiration can take place'
- All gas exchange surfaces will share the following properties;
- Permeable to Gases
- Moist so gases can dissolve and diffuse across the membrane
- 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
- Surface area
- Proportional to O2 supply by diffusion
- Rate of diffusion can be increased by;
- Increasing surface area
- Decreasing the diffusion pathway
- Increasing the steepness of the diffusion pathway
- Rate of diffusion can be increased by;
- Proportional to O2 supply by diffusion
- Volume
- Proportional to demand of O2
- Demand will increase with an increase in metabolic rate (as the organism increases in size)
- As the cell increases in size, eventually simple diffusion will no longer satisfy demand for O2
- Demand will increase with an increase in metabolic rate (as the organism increases in size)
- Proportional to demand of O2
- The smaller the animal, the larger the surface area:volume ratio
- The larger the animal the smaller the surface area:volume ratio
- Surface area
- Unicellular Organisms e.g. Amoeba
- Small, unicellular organisms
- Has a large surface area:volume ratio
- It is unicellular so has a short diffusion pathway
- Lives in water so the entire surface of the amoeba is moist
- Diffusion of gases occurs over the entire cell membrane
- The amoeba is unicellular, so the rate of uptake of O2 is fast enough to satisfy the demand for O2 by the organism
- Multicellular Organisms
- As organisms get larger, the demand for oxygen increases but surface area to volume ration decreases
- Diffusion pathways also become larger
- The demand for O2 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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