They are genes.
Alveoli
Because they are the lining of the lungs that begin the process of taking oxygen out of the air and into the blood stream. They are the parts that actually coe into contact with the "air" and are therefore called the functional part of the lungs.
Nephron units are located in the kidney cortex. They are the functional units responsible for filtering blood and regulating the electrolyte balance and fluid volume in the body. Each kidney contains thousands of nephron units.
Genes are the functional units of heredity.
One of the functional units of a myofibril is the sarcomere. The word sarcomere comes from the Greek words sarx, meaning flesh, and meros, meaning part.
DNA and RNA contain functional units known as nucleotides, which are composed of a sugar, a phosphate group, and a nitrogenous base. ATP (adenosine triphosphate) contains functional units called phosphate groups, which are crucial for the transfer of energy in cells.
cells are functional units
One million functional units
Cell of living organisms!
between functional units
I have no idea what you mean with "functional unit". The SI has units to measure lots of different things; basically there are seven base units (such as the meter, the second, and the kilogram), and several dozen derived units, i.e., units derived from the base units, for example meters/second for speed.