COELENTERATA PHYLUM (CNIDARIA)

*habitat-all are aquatic and mostly marine.they are solitary or colonial.
*body form- many coelenterates like obelia is a trimorphic colony having three kind of individuals.
    polyps:-nutritive zooids
    blastostyles:-budding zooids.
    medusae:-sexualzooids.
*symmetry- radial
*germ layer-diploblastic
*level of organization-tissue level
*body wall- it consists of two layers of cell epidermis and gastrodermis, and the gelatinous layer                              between them is mesoglea.the epidermis consists of many different cell:-
                     epitheliomuscular cell
                     cnidoblast
                     interstitial cell
                     nerve cell
                     sensory cell
*digestive tract-incomplete tract , the body cavity has only one opening
*digestion- both intra and extra cellular digestion
*respiration and excretion- diffusion by body surface.
*nervous system-premitive form of nervous system is found.
*skeleton-in some coelentrates calcareous exoskeleton or endoskeleton is found.
*reproduction-both sexual and asexual reproduction is found.
*development-the cleavage is holoblastic, and both direct and indirect development is found.
*cnidaria are divided into three classes on the basis of dominance of polypoid and medusoid phase.
   1. hydrozoa- polyp and medusae are found
   2. schyphozoa-they are represanted by medusae
   3. anthrozoa- they are represented by polyp form.

*some scientific and common names of coelentrates-
Obelia- sea fur
Physalia-portuguese man of war
Porpita Velella-by the wind sailor
Aurelia- jelly fish
Gorgonia-sea fan
Metridium-sea anemone
Alcyonium-dead man's finger
Tubipora- organ pipecoral
Astraea-star coral
Pennatula-sea pen

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