What species has the simplest known ribosome?

That would be prokaryotes (bacteria) The primary function of a ribosome is to translate the genetic information encoded in messenger RNA into functional proteins. read more

Piecing together the precise molecular structure of the ribosome has required decades of biological detective work by multiple laboratories. Aided by other proteins in the cell, ribosomes assemble new proteins according to genetic instructions. read more

Half-life of the ribosomes was measured by several researchers and it varies according to the physiological condition and the site. On average, ribosomes have half-life of 5-10 days in normal physiological conditions. References: 1. Nikolov EN, Dabeva MD, Nikolov TK. Turnover of ribosomes in regenerating rat liver. read more