Cnidaria, Annelida , Amphibia ,Reptalia

(1) State four important features of Phylum Cnidaria .                           Mark 4

 

Hydra, Obelia,Adamsia ,etc belongs to the Phylum Cnidaria and exhibit the following important  general characters:

(i) Body diploblastic :

    #outer epidermal ectoderm  and

    # inner gastrodermal endoderm.

  In between these two germ layers mesoglea is present.

(ii) Gastrovascular cavity  or digestion cavity opens only by mouth (i.e.anus absent) which is encircled by tentacles.

(iii) Nematocyst (stinging organelles) containing Cnidocyte cells are present in the body wall.

(iv) A few member organisms show dimorphism :

# Medusa (sexual phase) for pelagic existance and

#Polyp (asexual phase)for benthic existance .

(2) Classify Phylum Cnidaria upto sub-class level.                        4 marks

 Classification of Phylum Cnidaria (according to Ruppert & Barnes ,1994/6th Edn.):

Phylum : Cnidaria

  Class I : Hydrozoa

                  e.g. Hydra, Obelia,Physalia,etc.

  Class II: Scyphozoa

                  e.g. Aurelia, Pilema, etc.

  Class lll: Cubozoa

           Sub-class: Octocorallia/Alcyonaria

                  e.g. Gorgonia(sea fan),       

                  Alcyonium (Dead man's fingure)

 Class lV : Anthozoa

          Sub-class: Hexacorallina/Zoantharia

                 e.g. Adamsia(sea anemones),

                  Fungia(mushroom coral),etc.

(3) State four important features of Phylum Annelida .                 4 marks

Earthworm, Leech ,etc . belong  to Phylum Annelida and exhibit the following features

(i) Body shows bilateral symmetry with metameric segmentation  including a pre-segmental prostomium and a post segmental pygidium .

(ii) Body cavity true coelomate and lined by a peritonium or coelomic epithelium .

(iii)  Outer epithelium is covered by a cuticle and also have epidermal bristles or chaetae in bundles or singly.

(iv)  Metamerically arranged paired tubular Nephridia are the excretory organs.

(4) Classify Phylum Annelida.    3 marks

Classification , according to Marshal and Williams, 1972:-

Phylum :Annelida

       Class l : Polychaeta

            Sub-class: Errantia

                e.g. Nereis , Sabella,etc

            Sub-class: Sedentaria

                e.g. Arenicola

      Class ll :  Archiannelida

                e.g. Polygordius

      Class lll : Oligochaeta

                e.g. Metaphire

      Class IV : Hirudinea

                e.g. Hiruinaria

(5) General characters of  Amphibia.

(i)  Poikilothermal , body comprises a distinct haed with elongated trunk; neck and tail may or may not be present (Tail , if present, short and conical).

(ii) Skin smooth or rough , moist, naked and highly glandular( mucus gland and poison gland), have pigmented cells i.e. chromatophores .

(iii)   Skull dicondylic  ; eyelids and tympanum is present ; tongue often protrusible .

(iv)     Adult members respire by lungs or skin or by bucco- pharyngeal cavity , gills present during larval stage ; heart three chambered with two auricles and one ventricle .

e.g. Frog , salamandars, etc.

(6) Classification of Amphibia.

Classification 

( According to J.Z Young , 1981)

Class :Amphibia

   Sub-class: Labyrinthodonta 

                      (folded teeth)

                      e.g.

   Sub-class : Lepospondyli

                     ( Scale vertebrae)

   Sub-class: Lissamphibia

                     ( smooth amphibia)

             Order I: Anura ( no tail)

                 e.g. Indian toad , indian bull frog 

             Order Il : Urodela(with tail)

                 e.g. Salamandra, Triturus,etc.

             Order lll: Apoda(no limb)

                 e.g. Ichthyosis

(7) General characters of Reptilia.

(i)  Poikilothermal, skin dry, cornified and usually covered with epifermal  horny scales  or scutes , skin gland absent, skull is monocondylic .

(ii) Heart consists of two auricles and a partially divided ventricle ( exception ..in crocodiles , heart four chambered ).

(iii) Kidney metanephric , nephrostome  absent , uricotelic .

(iv) Usually oviparous , cleidoic eggs large and egg shell calcareous & porous for the exchange of gases.

(8) Classification of Reptilia.

(According to J.Z.Young,1981)

Class Reptilia

     Sub-class l.     Anapsida

                          e.g. Trionyx, Chelone, etc.

     Sub-class ll.    Synaposauria ( extinct )

     Sub-class lll.   Ichthyopterygia ( extinct )

     Sub-class lV.   Lepidosauria

                         e.g. Sphenodon puncyatus

                                S. guntheri, 

                                Lizadrs, Snakes 

     Sub-class V.    Archosauria

                         e.g. Alligator, Crocodile,

                                Gharials, etc.

     Sub-class Vl.   Synapsida (extinct)