Classification is the method used by scientists to order living organisms. All species have a unique classification that results in a binomial name. classification is used to make it easier for different species to be identified by scientists. The current system, the Three Domain System , groups organisms primarily based on differences in ribosomal RNA structure. Ribosomal RNA is a molecular building block for ribosomes . Under this system, organisms are classified into three domains and six kingdoms . The domains are Archaea, Bacteria, and Eukarya. The kingdoms are Archaebacteria (ancient bacteria), Eubacteria (true bacteria), Protista, Fungi, Plantae, and Animalia.
The system used for classifying organisms change due to new discoveries being constantly made making some organisms harder to classify into a specific kingdom or domain. This is why different criteria is being added so that newly discovered organisms can be classified. The original five kingdom system, called the binomial nomenclature, is no longer in use, it is now a six kingdom system. The modern classification uses the following six Kingdoms: Plantae Archaebacteria Eubacteria Protista Animalia Fungi The modern system has also expanded to three domains instead of the original two: Archaea Prokarya Eukarya.
The three domain classification system was created due to new evidence being found. In the old system of the five kingdoms all organisms were placed into one of these groups. In 1990, the three domain system was proposed.
In the three domain system, organisms with cells that contain a nucleus are placed in the domain Eukarya, this contains 4 of the five kingdoms. Organisms that were in the kingdom prokaryotae, which contain unicellular organisms that don’t have a nucleus, are separated into two domains. These are called Archaea and Bacteria. The lower hierarchy stays the same – kingdom, phylum, class, order, family,