Exchange surfaces

• Exchanging substances in a single celled organism is much quicker and easier than in a multicellular organism. This is due to there is a smaller distance to travel in a single celled organism. The substance only needs to diffuse through the membrane.
• Multicellular organisms can’t rely on diffusion like a single celled organism can, due to it being to slow, some cells are deep within the body.
• in multicellular organisms the metabolic rate is much higher meaning the demand for oxygen is higher.
• Without the exchange surfaces, diffusion would be too slow in multicellular organisms
• larger animals have a smaller surface area to volume ratio.
• The need for exchange surfaces depends on size, surface area to volume ratio and level of activity.
• All organisms need nutrients and oxygen to survive, they also need to be able to excrete waste products.
• A mouse has a larger surface area to volume ration, but an elephant has a smaller surface area to volume ratio.
• A good exchange surface has a large surface area as this increases the rate of diffusion. They also have thin walls as it decreases the diffusion distance. They also have a good blood flow as this helps maintain the concentration gradient for diffusion.