PORIFERA PHYLUM

SPONGES

*habitat- all sponges are aquatic, mostly marine, rarely fresh water, solitary or colonial. alla re sessile, attached to the substratum.
*body form- they are vase like, cylinderical, cup shaped, spherical, or disc like. their body is porous,the inhalent pore is called ostia and the exhalent pore is called osculum.
*symmetry.-they are asymmetrical.
*germ layer-diploblastic animal.
                     sponges are first multicellular diploblastic animal.
*level of organisation-cellular level
*body wall-consist of three layers:-
                     choanoderm (=gastrel layer)
                     mesohyl layer (middle layer)
                     pinacodern(outer layer)
*canal system-three types of canal system are-
                       asconoid canal system- simplest canal system. e.g.-leucosolenia
                       syconoid canal system- it is more complex than asconoid system.e.g.- sycon
                       leuconoid canal system- it is the most complex canal system.e.g.- spongilla
*digestion- interacellular digestion
*respiration- diffusion of gases through plasma membrane.
*excretion-removal of waste is also by diffusion with the help of plasma membrane.
*reproduction- both sexual and asexual(budding and gemmule) reproduction occur.
*development- development is indirect and includes a free swimming larva, the amphiblastula or                                  parenchymula.

*sponges are also called by their common names, some are mentioned here-
Sycon- scypha
Euplectella-the venus' flower basket
Spongia-bath sponge
Spongilla-fresh water sponge
Hyalonema-the glass rope sponge
Leucosolenia- orange pipe sponge

SPONGILLA

NOTOCHORD

notochord is mesodermally derived rod-liked structure formed on the dorsal side during embryonic development in some animals. animals with notochord are called chordates and animals without notochord is called non-chordates. e.g.-porifera to echinodermata.

SEGMENTATION

* in some animal the body part are divided into many similar segments, as like in earthworm . it has metameric segmentation.

COELOM (BODY CAVITY)

* the body cavity , which is lined by mesoderm is called coelom.

*presence or absence of coelom is very important in classification..

*coelomates- animal posses coelom is called coelomates.e.g- annelida, mollusca, arthropoda, echinodermata, hemichordata and chordates
.
*pseudocoelomates- the body cavity is not lined by mesodern and it is found in scattered form, such body cavity is called pseudocoelom and the animal possessing them is called pseuducoelomates. e.g.-aschelminthes

*acoelomates-the animal in which the body cavity is absent is called acoelomates. e.g.- platyhelminthes.

DIPLOBLASTIC AND TRIPLOBLASTIC

*diploblastic- animals in which the cells are arranged in two embryonic layers, an external ectoderm and internal endoderm are called diploblastic.e.g.-coelentreta.

*an undifferentiated layer mesoglea is present in between ectoderm and endoderm.

*triploblastic-those animal in which the developing embryo has a third germinal layer, mesoderm is called triploblastic.e.g.- platyhelminthes to chordates

SYMMETRY OF BODY OF ORGANISM

asymmetrical- sponges are asymmetrical.i.e. any plane that passes through the center does not divide them into equal halves.

radial symmetry- the plane passing through the central axis of the body divides the organism into two identical halves, it is called radial symmetry.coelentrata,ctenophora and echinodermata have this kind of body plan.

bilateral symmetry-the body can be divided into identical left and right halves in only plane, exhibit bilateral symmetry.

RADIAL SYMMETRY

BILATERAL SYMMETRY

LEVEL OF ORGANISATION OF CELL IN BODY

* all members of animalia are multicellular and they exibit different level of organisation.
*cellular level-in sponges the cell are arranged in loose aggeregation.
   tissue level- in coelentrata the cell arrangement are more complex. here, the cell performing the                             same function are arranged into tissue.
   organ level-in platyhelminthes the tissue are grouped together  to form organs. each organ                                       specialised for a particular function.
   organ system level-in animals like annelida,arthropods,mollusca,echinodermata and                                               chordates,organ are associated to form funtion system. each system concern with a                              specific physiological function.this is called organ system level.
*in organ system level, the organism are classified on various basis like open and close circulatory system, complete and incomplete digestive system etc.