Retrogressive Metamorphosis in Urochordates Metamorphosis is a change from the juvenile to adult stage in which larval stage is quite different from the adult stage. In retrogressive metamorphosis the larva possesses advanced characters which are lost during the development and the adult is either sedentary or degenerated with primitive characters. Urochordate adults, being sedentary show degenerative characters while the free swimming tadpole larva shows advanced chordate characters which are lost during metamorphosis. Parasitic crustaceans, like Sacculina and copepod parasites and stylopids and scale insects (Insecta) also show retrogressive metamorphosis. Retrogressive Metamorphosis in Herdmania The tadpole larva of Herdmania is only 1-2 mm long when it hatches out of the egg. It does not feed and hence has only 3 hours of survival during which it has to swim about in search of a suitable substratum for attachment. The larva needs advanced features for its free swimming existence,...
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Q:-1 Describe navigation in fishes and birds. Explain its urge and control also. (20) Q:-2 What is vitamin? With suitable example describe different types of it. Describe the biosynthesis of Vitamin - D. (20) Q:-3 Define co-enzymes. How they are regulating the activity of enzymes? Describe with suitable examples. (15) Q:-4 What is FAP? How it is controlling development in various animals? (10) Q:-5 Describe various types of Biological clock. (20)
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