Human body is not just a collection of cells and tissues. It contains various specialised cells and tissues for various functions and life processes. Diffusion can be applicable or be useful only in unicellular organisms where such cell system is absent

Diffusion and Oxygen Requirements of Multicellular Organisms

Multicellular organisms like humans require a constant supply of oxygen to carry out various life processes. Oxygen is used in cellular respiration to produce energy for the body. Diffusion is the process by which gases like oxygen move from areas of high concentration to areas of low concentration. While diffusion plays a crucial role in the movement of oxygen in unicellular organisms and small organisms, it is insufficient to meet the oxygen requirements of large, complex organisms like humans.

Limitations of Diffusion

There are several limitations of diffusion that make it insufficient to meet the oxygen requirements of multicellular organisms like humans:

Surface Area to Volume Ratio

One of the primary limitations of diffusion is the surface area to volume ratio. As organisms become larger, their volume increases at a much faster rate than their surface area. This means that there is less surface area available for diffusion to occur. As a result, diffusion cannot supply the required amount of oxygen to all the cells in the body.

Distance

Another limitation of diffusion is the distance that oxygen has to travel. In larger organisms, the distance between the respiratory surface and the cells that require oxygen is greater. This means that oxygen has to diffuse over a longer distance, which makes it slower and less efficient.

Rate of Diffusion

The rate of diffusion is also limited by the concentration gradient. As the concentration gradient decreases, the rate of diffusion also decreases. In larger organisms, the concentration gradient is much lower, which means that the rate of diffusion is slower.

Conclusion

In conclusion, while diffusion is an important process for the movement of gases like oxygen in small organisms, it is insufficient to meet the oxygen requirements of large, complex organisms like humans. To meet their oxygen requirements, multicellular organisms like humans have evolved specialized respiratory systems that allow for the efficient exchange of gases.