Ch -4 Animal kingdom
Ch:4 Animal kingdom Millions of species of animals have been described and it becomes more necessary to classify them to assign a systematic position. Animals are classified on the basis of arrangement of cells, body symmetry, nature of coelom, pattern of digestive, circulatory and reproductive system. Incomplete digestive system has one opening but complete digestive system has two opening- mouth and anus. Open circulatory system- blood is pumped out of heart and cells and tissue are directly bathed in it. Closed circulatory system- blood is circulated through arteries, veins and capillaries. The animals in which cells are arranged in two embryonic layer, external ectoderm and internal endoderm are called diploblastic . Eg. Porifera and Cnidaria. The animals in which developing embryo has a third germinal layer, mesoderm besides ectoderm and endoderm are called triploblastic. Eg. Platyhelminthes, Chordates. The body cavity which is lined by mesoderm is call