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.
Observational studies are ones where researchers observe the effect of a risk factor, diagnostic test, treatment or other intervention without trying to change who is or isnât exposed to it. Cohort studies and case control studies are two types of observational studies. Cohort study: For research purposes, a cohort is any group of people who are linked in some way. For instance, a birth cohort includes all people born within a given time frame.