We should choose the basic characteristics among several other characteristics for developing a hierarchy of classification. The basic characteristics that are chosen are free of any other characteristics in their effects on the form and function of the organism. The characteristics in the next level would be dependent on the previous one and would help in deciding the variety in the next level. In this way, the entire hierarchy of commonly related characteristics would be build to be used for classification. This helps in the establishment of hierarchy of characteristics.
Following are the advantages of classifying organisms:
All the vertebrates are bilaterally symmetrical, triploblastic, coelomic, and segmented with complex differentiation of body tissues. Following features are common to all chordates:
Vertebrates are grouped into following five classes:
Criteria for deciding divisions in plants are:
Criteria for deciding sub-groups in animals are:
Kingdom Animalia is divided into two major groups on the basis of the presence or absence of a notochord.
Non-chordates do not possess a notochord, while all members of a phylum chrodates possess a notochord.
Non-chordate is further divided into subgroups on the basis of the following features.
On the basis of the above features, non-chordates are divided into the following sub-grpups.
Porifera, Coelentrata, Platyhelminthes, Nmatodes, Annilides, Molluscs, Arthropoda and Echinodermata
All members of the phylum chordate possess a non-chordate. However, some animals such as Balanoglossus, Amphioxus, Herdmanina, etc have a notochord which is either absent or does not run the entire length of the animal’s body. Therefore, these animals are kept in a separate subphylum called Protochordata.
The rest of the chordates are included in the subphylum vertebrata. The members of the sub-phylum vertebrata are advanced chordates. They are further categorised into five classes, Pisces, Amphibia, Reptilia, Aves and Mammalia.
The kingdom Plantae is divided into five main divisions: Thallophyta, Bryophyta, Pteridophyta, Gymnosperms and Angiosperms.
The classification depends on the following criteria:
In 1959, Robert H Whittaker proposed a five kingdom classification of living organisms on the basis of cell structure, mode and source of nutrition and body organisation as main features. The five kingdoms proposed by Whittaker are Monera, Protista, Fungi, Plantae and Animalia.
The basis for grouping organisms into five kingdoms:
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