zoology Arena

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,...

Hemichordata status                           Introduction Hemichordata was till recently treated as the sub phylum of the phylum Chordate but is now regarded to be the independent phylum of invertebrates very close to the phylum Echinodermata. The peculiar characteristics of the animals belonging to Hemichordata are as follows, Enterocoelus coelom Pharyngeal gill slits Buccal diverticulum (earlier considered as notochord) Vermiform body divisible into three regions – proboscis, collar, trunk The phylum hemichordate includes a small group of soft, primitive and marine chordates called as acron worms or tongue worms. Most familiar genus of this phylum is Balanoglossus which belongs to the class Enteropneusta. Other closely related genera are Saccoglossus, Glossobalanus etc. The class Enteropneusta was established by Gegenbaur in 1870. Since then due to the peculiar anatomical organisation and embryology, Hemichordata have...

                             Week-3 Instructions:- There are Seven questions divided in Two sections. All questions are compulsory. Adhere to world limit wherever specified. The number of marks carried by a question is indicated against it.                              Paper I Q:-1 Write Notes on the following in about 150 words each: (10X5 =50) a) Phratry b) Society and culture c) Lineage and clan d) Insect taboo e) Cultural relativism Q:-2 Discuss the cardinal points of descents and culture. Explain segmentary lineage and territoriality. (20) Q:-3 Explain various types of marriages in Vedic culture. How various cultural and awakening movements influenced the institutional form of marriages. (20) Q:-4 Discuss various laws of succession in India.  What is the impact of industrialization on Famili...