Question

explain the 'three domain system' of classification

Answer 1

Answer:

The three domains are the Archaea, the Bacteria, and the Eukarya.

Explanation:

More recently various fusion hypotheses have begun to dominate the literature. One proposes that the diploid or 2N nature of the eukaryotic genome occurred after the fusion of two haploid or 1N prokaryotic cells. Others propose that the domains Archaea and Eukarya emerged from a common archaeal-eukaryotic ancestor that itself emerged from a member of the domain Bacteria. Some of the evidence behind this hypothesis is based on a "superphylum" of bacteria called PVC, members of which share some characteristics with both archaea and eukaryotes. There is growing evidence that eukaryotes may have originated within a subset of archaea. In any event, it is accepted today that there are three distinct domains of organisms in nature: Bacteria, Archaea, and Eukarya. A description of the three domains follows.

Intermediaries between Bacteria, Archaeae, and Eukarya Domains?

There is a "superphylum" of bacteria called PVC, referring to the three members of that superphylum: the Planctomycetes, the Verrucomicrobia, and the Chlamydiae. Members of the PVC, while belonging to the domain Bacteria, show some features of the domains Archaea and Eukarya.

Some of these bacteria show cell compartmentalization wherein membranes surround portions of the cell interior, such as groups of ribosomes or DNA, similar to eukaryotic cells. Some divide by budding or contain sterols in their membranes, again similar to eukaryotes. Some lack peptidoglycan, similar to eukaryotes and archaea. It has been surmised that these bacteria migh be an intermediate step between an ancestor that emerged from a bacterium (domain Bacteria) and an archael-eukaryotic ancestor prior to its split into the domains Archaea and Eukarya