Zoology for UPSC and State PSC exams
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— Tunicates (Herdmania, Ascidia, Pyrosoma) General CharactersLarvae contain all chordate characteristics while adults only exhibit pharyngeal pouches.Marine animals. Some are solitary, some are colonial.Sessile as adults but motile during larval…
Habits and Habitat Solitary / Colonial, Tubiculous, Worm like marine animals with segmented body.Moves in its burrow by cilia covering its body surface. External Morphology Cylindrical body:-Proboscis – conical –…
Salient Feature Chordates Non-Chordates Symmetry Bilateral Radial, bi-radial, bilateral, no symmetry Metamerism True metamerism True or Pseudo-metamerism, or absent Post anal tail Usually present Usually absent Organisation Organ system level…
Chordates originated from invertebrates some 500 million years ago during Cambrian Explosion.Chamberlain: Evolved from freshwater forms as all modern chordates have glomerular kidneys that are designed to remove excess water…
Chordate evolution is built upon traits that evolved in invertebrates — bilateral symmetry, cephalisation, segmentation, coelom, gut tube.Highest (most advanced) phylum among the 30 odd phyla in the animal kingdom.All…
General Characters Pentamerous radial symmetry, derived from larval bilateral symmetry.Body consists of an indistinct disc, from which radiate 5 elongated and tapering rays or arms.Coloration is variable.Body strongly flattened with…
Echinodermata represent the most complicated metamorphosis in the course of development.Larva have bilaterally symmetry and have a free-swimming, planktonic existence.Adults have radial symmetry. Class I: AsteroideaBipinnaria LarvaAfter hatching, the larva…
All molluscs, except the Gastropoda, retain ancestral bilateral symmetry of the body. Mantle cavity lies posteriorly or laterally.Gastropods have an asymmetrical body with mantle cavity lying anteriorly, and the shell…
Shell is a protective skeleton, which forms a characteristic feature of molluscs.Usually external, but sometimes internal.Derived from the mantle of the veliger larva. Structure of ShellsPeriostracum: Outermost pigmented layer, made…
Cutaneous Simplest method. Respiration by moist integument.Usually in Mollusca that have no differentiated respiratory organs — Scaphopoda, Aplacophora.Respiration occurs through the whole body surface.Restricted when body is covered with a…