The study of evolution of organisms based on evolutionary and genetic relationships among organisms, led to the emerge of phylogenetic classification or cladistics.

DNA hybridization (measures the degree of genetic similarity between pools of DNA sequences), DNA fingerprinting (to identify an individual from a sample of DNA by looking at unique patterns in their DNA), Restriction Fragment Length Polymorphisms (RFLP) analysis (difference in homologous DNA sequences that can be detected by the presence of fragments of different lengths after digestion of the DNA samples), and Polymerase Chain Reaction (PCR) sequencing ( to amplify a specific gene, or portion of gene,) are used as taxonomical tools.

Kingdom Monera includes bacteria which are prokaryotic organisms lacking a nuclear membrane.

(i) It is a group of closely related species which have evolved from a common ancestor.
(ii) Types.
(a) Monotypic:
In some genus there is only one species.
Eg: Red Panda is the only species in the genus Ailurus: Ailurus fulgens.
(b) Polytypic:
There are more than one species in the genus
Eg: 'cats' come under the genus
Felis which has a number of closely related species like
Felis domestica (domestic cat)
Felis margarita (jungle cat)
Felis silvestris (wild cat)

1. Carl Woese and his coworkers classified organisms based on the difference in 16s rRNA genes.
2. This system adds the taxon 'domain' higher than, the kingdom.
3. Prokaryotes are separated into two domains - Bacteria and Archaea and all the Eukaryotes are placed In the domain Eukarya