WHY IS DIFFUSION INSUFFICIENT TO MEET THE OXYGEN RECQUIREMENT OF MULTICELLULAR ORGANISMS LIKE US?
that question would have been much more easier to read it it wasn't it capitalization.
Think of the organisms that use diffusion for gas exchange. Most of them have a very high surface area to mass ratio.
I'll give you a big hint, there's a relationship between speed of diffusion and the distance over which something is being diffused.
Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration. It relies on the random thermal motion of molecules to distribute them evenly throughout a space. While diffusion is an efficient means of transport over short distances, it becomes less effective over longer distances or when the concentration gradient is too large.
In the case of multicellular organisms like humans, the distance between the site of oxygen absorption (such as the lungs) and the cells that need oxygen throughout the body is substantial. Additionally, our cells have a high demand for oxygen to carry out essential metabolic processes. This creates a significant concentration gradient, with a higher concentration of oxygen in the lungs and a lower concentration in the cells.
If diffusion were the only mechanism for oxygen transport in our bodies, it would take too long for oxygen to diffuse from the lungs to the distant cells, and the oxygen supply would not meet the cells' requirements in a timely manner. This is why multicellular organisms have evolved specialized circulatory systems, such as the cardiovascular system in humans, to facilitate the efficient transport of oxygen and other vital substances.
The cardiovascular system uses the heart as a pump to circulate blood and carries oxygen-rich blood from the lungs to the tissues through a network of blood vessels. This allows for a much faster and more precise delivery of oxygen, ensuring that the oxygen requirements of multicellular organisms like us are met efficiently.
In summary, while diffusion is a natural process for the movement of molecules, it is insufficient to meet the oxygen requirements of multicellular organisms due to the significant distances between the oxygen source and the oxygen-demanding cells. That's why more complex transport mechanisms, such as the circulatory system, have evolved to ensure efficient oxygen delivery.