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development of a vertebral column or back bone (e.g. mammals, birds, fish, frogs and reptiles) and they are classified as VERTEBRATA. The others are considered as lower chordates or protochordates. Thus INVERTEBRATES include all non-chordata and lower chordates.
Some of the main characteristics of Vertebrata are:
Possession of back bone formed of a chain of vertebrae; presence of a skull (cranium) enclosing the brain; possession of brain and spinal cord; presence of red blood cells with haemoglobin; presence of lungs or gills for respiration; sexes are always separate.
A more up-to-date and convenient method of classifying the animal kingdom is to divide it into:1
1. Sub-kingdom: Protozoa-organisms with a body which is not divided into cells; they are ACELLULAR
2. Sub-kingdom: metazoa organisms with a body sub-divided into number of cells; they are multicellular.
1. The following is the schematic diagram of classification:
ANIMALIA
PROTOZOA
1. Phylum Protozoa
Branch 1 PARAZOA Porifera Coelenterata Platyhelminthes
4. Phylum
5. Phylum Hemathelminthes
6. Phylum
Annelida
7. Phylum
Arthropod
8. Phylum Mollusca
9. Phylum Echinodermata 10. Phylum Chordata
2. Phylum
3. Phylum
:
Sub-phylum Vetebrata
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METAZOA
Branch - 2 ENTEROZOA
(i) class Pisces (Fishes) (ii) class Amphibia (amphibians) (iii) class Reptilia (reptiles) (iv) class Aves (birds) (v) class: Mammalia (mammals)
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