LEVELS OF ORGANISATION ~All members of animalia are multicellular ~All of them do not exibit same pattern of organisation of cells. ~The performing the same function are arranged into tissue, called tissue level. ~A still higher level organization i.e organ level. ~In animals like Annelida,Arthropods,Mollusca,Echinoderm, and chordata organs have associated to form functional system,each system concerned with a specific physiological function. these pattern is called organ system level of organisation. ~a complete digestive system has two openings mouth and anus. similarly the circulatory system may be of two types: (i) open type.: in which though blood is pumped out of the heart and the cells and tissues I directly bath in it . (ii) close type.: in which the blood is circulated through a series of vessels of varying diameter.

SYMMETRY ~animals can be categorized on the bases of the symmetry. sponges are mostly or asymmetrical ~when any plane dad passes through the center axis of the body divides the organism into two identical halves, it is called radial symmetr. ~where the boarded can be divide into identical halves is only plane, exhibit bilateral symmetry.

DIPLOBLASTIC AND TRIPLOBLASTIC ORGANISATION ~animals in which the cells are arrange into embryonic layer and external ectoderm and internal ectoderm is called diploblastic animal. ~the animals in which the developing embryo has 3rd terminal layer mesoderm in between the ectoderm and endoderm are called triploblastic animals.

COELOM ~the body cavity which is line by mesoderm is called COELOM ~animal possessing Coelom are called Coelomates. ~example: annelids, molluscs, orthropoda, echinoderms, hemichordata, and chordata. ~the animals in which the body cavity is absent is called acoelomate. ~the body cavity is not lined by Mesoderm,instead,the Mesoderm is present as scattered pouches in between the ectoderm and endoderm such a body cavity is called pseudodocoelomates.

SEGMENTATION ~the body is externally and internally divided into segments with a serial repetition of the list organs. for example the in earthworm, the body shows these pattern called metameric segmentation and the phenomenon is known as metamerism.

NOTOCHORD ~notochord is measodermlly derived rod like structure formed on the dorsal side during everyone development in and animal ~animals with no code are called chordates and those animals which do not form the structure are called non-chordates.