Diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration. While diffusion can effectively transport oxygen to the cells in the outer layers of a multicellular organism, it is not sufficient to meet the oxygen requirements of all the cells in the organism, especially those located in the deeper tissues.In multicellular organisms like humans, diffusion alone is insufficient to meet the oxygen requirements because of the organism’s size and complexity.
7 Important Reasons for Why Is Diffusion Insufficient to meet the Oxygen Requirements of Multicellular Organisms Like Humans
- Oxygen demand – The oxygen requirements of a multicellular organism like a human are much greater than those of a single celled organism, and diffusion alone is not able to supply enough oxygen to meet these demands.
- Distance – The distance that diffusion must cover becomes increasingly larger as the organism grows larger and more complex. In a multicellular organism, oxygen must travel from the lungs or gills (where it is taken in) to all the cells in the body, a distance that becomes increasingly difficult for diffusion to cover as the organism grows larger.
- Resistance to Oxygen Flow– Diffusion alone cannot overcome the resistance to oxygen flow posed by the dense network of blood vessels that are required to supply oxygen to all the cells in a multicellular organism.
- Cell specialization – Multicellular organisms like humans have cells that are specialized for different functions. These cells may require different amounts of oxygen, which makes it difficult for diffusion alone to supply the right amount to each cell.
- Low-oxygen Environment- Diffusion happens based on the concentration gradient so when the organism lives in a low-oxygen environment (such as high altitudes) diffusion becomes insufficient for meeting the oxygen requirements.
- Tissue thickness – The cells in multicellular organisms are often arranged in layers, making it more difficult for oxygen to diffuse through the layers to reach the cells that need it.
- Diffusion alone does not take into account the possibility of oxygen demand fluctuating over time, and is not able to adjust to meet changes in oxygen needs.