Biological Classification of Echinodermata and Mollusca

                                                         Kingdom Animalia

Phylum Echinodermata:-

Echinus (Spines) dermal(Skin or layer ), means spines bearing animals.

Echinodermata

(1)   These are exclusively marine.

(2)   Organ level of organization.

(3)    Radial symmetry with the Bilateral larval stage.

(4)    Body without segmented.

(5)    Coelom present.

(6)   Triploblastic and Schizocoelom.

(7)   Presence of Tube feet.

(8)   Water The vascular system is present

(9)   The shape of the body is star-shaped, flat and elongated.

(10)  The function of Water Vascular System is  (Hint:- LCR circuit)  

                                         Locomotion, Circulation, and Respiration.

(11)     Blood has no Pigment or blood is colorless.

(12)     Digestive of the system is Complete.

(13)     Sexes are Monoceious or may be Diecious.

(14)     Development is indirect with the formation of the larval stage

(15)     Sea cucumber larva is “auricularia “.

This Phylum is divided into 5 classes:-

Asteroidea:-

(1)  The body is flattened star-shaped with five arms

      (2) They possess tube feet with a sucker

      (3) Presence of calcareous plates and movable spines.

      (4) Respiratory organ: papulae

        Examples: Asterias (Starfish), Astropecten, Zoraster, Oleaster

 Ophiuroidea:-

      (1)  The body is flat with pentamerous disc

      (2)   They possess a long arm which is sharply demarcated from the central disc.

      (3)    They possess tube feet without sucker

      (4)  Anus and intestine are absent

      (5)    Respiratory organ: Bursae

         Examples: Ophiderma, ophiothrix, Astrophyton, Amphuria, etc

 Echinoidea:-

       (1) The body is disc-like hemispherical

         (2)They are devoid of arms or free-rays.

         (3)They possess tube feet with a sucker

.        (4) They possess compact skeleton and movable spines

.          Examples: Echinus (Sea urchin), Cidaris, Arbacia, Echinocardium. Diadema

Holothuroidea:-

  (1) The body is elongated in the oral-aboral axis and it is like cucumber.

  (2) They have no arms, spines, and pedicellariae.

   (3) The tube feet are sucking type which is modified into tentacles and form a circle  

around the mouth.

   (4)  Respiratory organ: cloacal respiratory tree

    Examples: Cucumaria (Sea cucumber), Holothuria, Mesothuria, etc

 Crinoidea:-

     (1)Body is star-shaped

     (2)Some of the forms were extinct and living forms.

     (3)Arms bifurcated, with two pinnules.

     (4)They have tube feet without suckers

        Examples: Neometra, Antedon, Rhizocrinus, etc

Phylum Mollusca:- 

                      Soft-bodied Organism With a covering of cavity is called Molluscan

Mollusca

   (1)   Infolded A skin forms hard covering on the surface of the Mental cavity.

   (2)  Schizocoelom type of Coelom.

   (3)  Organ Level of organization.

   (4)  Bilateral symmetry.

     (5)  Closed circulatory system.

     (6)  Respiration is by Gills (Ctnidia) Present in Mental cavity.

     (7)  Excretion by a Pair of metanephridia.

     (8)  The heart consists of One Auricle and one ventricle.

     (9)  Nervous the system consists of Three pair of Ganglia,(cerebral, visceral, and pedal).

(10) Reproduction by Fusion of gametes.

     (11) Development may be direct or indirect by Trochophore larva.

      (12) Fertilization external or Internal.

Mainly this Phyla is classified into 3 classes, Total 6 classes but we study only 3 classes.

             

(1) Gastropoda
(2) Pelecypoda
(3) Cephalopoda

 (1) Pelecypoda:-

               (1)  Habitat: mostly marine

               (2) They burrow in mud and sand.

               (3)  Symmetry: bilateral and the body is laterally compressed.

                (4)  No distinct head

                  Examples: Mussels, Unio, Mytilus

     (2) Gastropoda:-

                  (1)Habitat: These are either aquatic or terrestrial

                    (2)  They possess a spiral shell.

                    (3) The foot is large and flat.

                    (4) The Head is well developed with tentacles and eyes.

                    Examples: Hilex (Snail), Limax (Slug), Pila (Apple snail).

        (3)   Cephalopoda

       (1)  Habitat: mostly marine.

       (2) They are adapted for swimming.

                    (3)The foot is modified into eight to ten long tentacles in the head region.

                    (4)The shell is either external, internal, or absent.

                    Examples: Octopus, Loligo, Sepia, spirula, Nau