Metals are classified as base metal, such as iron and aluminum  and precious metal, such as gold and silver. We all love precious and detest base.

The baseness of a metal, such as iron, comes from its abundance. The abundance of something also allows it to form a foundation of structures or systems. So base also means foundation.

If something is basic, it can be mundane; it can also be fundamental. When we say some laws are basic in nature or in societies, we mean these laws are very important. So base, in the end, turns out to be very important.

This is also true in biology. Iron, a base metal, plays fundamental roles in life. Our whole body is covered with skin to prevent infection from bacteria. There is one exception, eyes. How can our eyes avoid infection without the protection of skin? Some molecules on the surfae of the eyes constantly collect any iron ions and remove them. So the surface of our eyes is devoid of iron ions. Iron is an essential ingredient for life. Bacteria could not survive without iron. That is how naked eyes can avoid infection from bacteria.

Let's stick to the base and basic so we can connect to the most fundamental part of life.