Question

The domain is
1. Eukaryota
2. Archaebacteria
3. Eubacteria
A. 1 only
B. 2 only
C. 3 only
D. 1 and 3
E. 1, 2 and 3

Answer 1

The hierarchial system of classification was done by Whittaker which is followed today generally. It divides organisms into rankings. As we go down the hierarchy, the specifications increase, and the number of animals decreases. As we go up the hierarchy, the number of species increases. But the advancement in the system has changed the upper rankings.

Step by step answer: The system of classification of the Whittaker was followed for a very long time. Then came the Three Domain system, it was introduced by Carl Woese in 1990. Domain refers to the broadest taxonomic category having one or more kingdoms.
According to this system, there are domains called archaea, bacteria, and eukaryote.
The major difference is at the splitting of archaea from bacteria.
Eukaryote has now fungi, plants, animals, flagellates, ciliates, slime moulds etc.
Archae has Methanosarcina, Methanobacterium, Thermococcus, Methanococcus, etc.
Bacteria include gram positives, cyanobacteria, aquifex, planctomycetes, proteobacteria, etc.
Option A: 1 only: It has archaea and eubacteria, both as their domains.
Option B: 2 only: the eukaryote and eubacteria are also domains.
Option C: 3 only: archaea and eukaryotes are the domains also.
Option D: 1 and 3: Archaebacteria has always been a wide domain.
Option E: 1, 2 and 3: All the three form the 3 domain system.
So the answer is option E: 1, 2 and 3

Note: The eukaryotic domain has all the membrane-bound organelles and nuclei organisms. The archae is the oldest/primitive domain of bacterias. The bacteria which were not included in the archae are now placed under the bacteria/ eubacteria domain.