7.1 Specialised exchange surfaces

Amoeba are microscopic organisms, so all oxygen and carbon dioxide can be exchanged with the external environment by diffusion through the cell surface because the distance travelled is so small. Their metabolic activity is relatively low, meaning their oxygen demands (and carbon dioxide production) are low, Furthermore, their SA:V ratio is large, meaning gases can be exchanged quickly enough through diffusion.

As SA:V ratio increases, metabolic activity increases, meaning more oxygen is required and more carbon dioxide is produced. In order for oxygen demands to be met, specialised exchange surfaces must be employed. These have evolved over time and have certain features…