Honours / Core Course (CC)

 
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NON CHORDATE II : COELOMATES
INTRODUCTION
Evolution of Coelom
ANNELIDA

General characteristics and Classification up to classes (Ruppert and Barnes, 1994)

 

Excretion in Annelida through nephridia

A Nephridium is tubular coiled structure. It starts from a rounded funnel shaped structure called nephrostome. The nephrostome opens in a coiled tube called nephridial tubule which is lined with cilia.

The nephridial tubule opens outside the body through a small opening called nephridiopore. The body fluid of earthworm rich in nitrogenous wastes enters the nephridium through nephrostome and passes into nephridial tubule. In the nephridial tubule the useful substances present in fluid are absorbed. The remaining fluid containing high percentage of nitrogenous wastes is excreted out of the body through nephridiopore with the help of movements of cilia.

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Metamerism in Annelida

Q.What do you mean by enterocoelous theory of coelom origin?

According to this theory (Sedgwick,1884)coelom is associated with

(i) The origin of metameric segmentation.

(ii) The origin of coelom took place from the gastric pouches of some ancestral anthozoan coelenterates and they remain separated from the main gastric cavity and arranged in linear fashion.

(iii) Gastric pouches transformed into coelomic pouches in the protocoelomates.

(iv) First 4 gastric pouches are developed in ancestral medusoid coelenterates.

(v) Further division of 2 pouches resulted into 3 pairs of coelomic cavities (protocoel, mesocoel and metacoel in the protocoelomates).

(vi) Loss of protocoel (anterior pouch) and mesocoel (lateral 2 pouches) leads to the formation of unsegmented coelomates.

(vii) Later subdivision of metacoel (posterior pouch) produces segmented annelids.

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ARTHROPODA

General characteristics and Classification up to classes (Ruppert and Barnes, 1994)

 

Insect Eye (Cockroach only)

Q.State the mode of action in apposition eye.

i)Light entering a given cornea is confined by the screening pigment to one ommatidium, stimulates the rhabdomes of adjacent ommatidia.

ii)An eye in apposition mode functions well in bright light and permits the greatest resolution of the image.

iii)Each point of light stimulates one ommatidium and sends one signal to the brain.

iv)That point is registered by the brain as one point in the mosaic image.

ii)Less than 1% of the light reaching a rhabdome comes from other ommatidia (e.g. as in apposition eye sof honeybees and locusts)

 

Respiration in Prawn and Cockroach

Q.What is branchiostegite?

Gill chamber in prawn is covered by the lateral extension of carapace, which is called as branchiostegite.

Prawn respires in the aquatic medium and it carries 3 sets of organs for the purpose—lining of the branchiostegite, epipodites and gills. All these organs are enclosed within a special chamber on each side of the cephalothorax which is called gill chamber.

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Metamorphosis in Lepidopteran Insects

Social life in Termite

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ONYCHOPHORA
General characteristics and Evolutionary significance
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MOLLUSCA
General characteristics and Classification up to classes (Ruppert and Barnes, 1994)

General characteristics and Classification up to classes (Ruppert and Barnes, 1994)

 

Q.What is Osphradium ?

The osphradium is an olfactory organ in certain molluscs, linked with the respiration organ. The main function of this organ is thought to be to test incoming water for silt and possible food particles. Present in pair. Its receptor cells monitor the water entering the mantle cavity for chemicals and perhaps for sediment.

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Nervous system in Pila sp

Torsion in Gastropoda

 

Feeding and respiration in Pila sp

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ECHINODERMATA
General characteristics and Classification up to classes (Ruppert and Barnes, 1994)

General characteristics and Classification up to classes (Ruppert and Barnes, 1994)

Water-vascular system in Asterias

Q.What is stone canal?

Calcareous matter made canals, surrounded by axial sinuses( wider canal) . They connect ring canal to the madreporite, running across the body cavity.

Echinoderm larva and affinities with chordates

Q.State important features of a deuterostome larval.

i. Pattern of cleavage- Radial.

ii. Blastopore- becomes the anus in adults.

iii. Coelom- follows the enterocoelic theory.

iv. Example- larval form of Echinoderms and Chordates.

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HEMICHORDATA

General characteristics of phylum Hemichordata.

Relationship with non-chordates and chordates

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Q.What is eucoelom ?

Coelom, or true coelom is a fluid-filled cavity that develops within the mesoderm and is lined by mesodermal epithelium called peritoneum. The outer wall of the coelom is called the parietal, or somatic peritoneum, and the portion that covers the internal organs suspended within the cavity including the gut is called the visceral, or splanchnic peritoneum. Enterocoelomates of animal kingdom are echinoderms, hemichordates and chordates.

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