Introduction (from Wikipedia). The Archaea constitute a domain or kingdom of single-celled microorganisms. These microbes are prokaryotes, meaning that they have no cell nucleus or any other membrane-bound organelles in their cells. Bacteria constitute a large domain of prokaryotic microorganisms.ut it was discovered that archaea have a distinct evolutionary history and biochemistry compared with bacteria. The similarities are that archaea and eubacteria are single-celled organisms that do not have a nucleus or organelles.
cohort noun [C ]. âº a âgroup of âpeople who âshare a characteristic, usually age: About 42% of women in this age cohort have a college degree. This year's cohort of âgraduates will have particular difficulties âfinding âjobs.ohort noun [C ]. âº a âgroup of âpeople who âshare a characteristic, usually age: About 42% of women in this age cohort have a college degree. This year's cohort of âgraduates will have particular difficulties âfinding âjobs.
A retrospective cohort study, also called a historic cohort study, is a longitudinal cohort study that studies a cohort of individuals that share a common exposure factor to determine its influence on the development of a disease, and are compared to another group of equivalent individuals that were not exposed to that factor.