Classification of Animal Kingdom
Animals are those
organisms which are eukaryotic, multicellular and heterotrophic in their mode
of nutrition. Except few, most animals are mobile and do not have cell wall.
Multicellular
animals are called Metazoa which have been divided into two
branches: Parazoa and Eumetazoa.
·
In Parazoa, the body of animal is made up of
loose cells, have poorly differentiated tissues and have no organ or digestive
cavity. E.g sponges.
·
In Eumetazoa the cells are properly
arranged into tissues and organs. It is further classified on the basis of (a)
the number of germ layers present in the embryo; (b) the symmetry of the body
of the organism; and (c) mode of origin of mouth. Those animals which have two
germ layers in the embryo are called diploblastic animals and
those having three germ layers are called triploblasticanimals.
In diploblastic
animals, the outer cell layer is called ectoderm, while the inner
layer is called endoderm and both of these germ layers enclose
a non- cellular jelly-like layer, the mesoglea. The
triploblastic animals have three germ layers, namely ectoderm, mesoderm
and endoderm.
The two sides of
the body are mirror images of one another. Such body symmetry type is
called bilateral symmetry. Some animals have radial body
symmetry i.e having similar parts in a regular pattern around a
central axis.
Two types of
animals have been recognised on the basis of origin of mouths: Protostomia (mouth
arising from or near the blastopore of gastrula; gastrula is an embryonic
stage) and Deuterostomia (mouth arising anteriorly at
some distance from the blastopore).
Further, based on
the presence or absence of body cavity or coelom, animals are
groups into acoelomata, pseudocoelomata and coelomata. The acoelomates do not
have body cavity because the space between the body wall and digestive tract is
filled with parenchymatous tissue. Also, these tissues have a cavity between
the body wall and digestive tract but this does not arise from the mesoderm and
is not lined by epithelial cells. The Coelomates have true
body cavity which originates from mesoderm and is lined by epithelial cells of
mesodermal origin.
For further
understanding refer below:
 |
Examples of main phyla of kingdom Animalia are as follows:
·
Phylum 1 Porifera (porus- pore,
ferre- to bear; ‘organisms with holes’)E.g: Sycon, Euplectella (Venu’s flower
basket), Hyalonema (rope sponge), Spongillia, Euspongia ( Bath sponge) etc.
·
Phylum 2 Cnidaria or Coelenterata ( koilos-
hollow, enteron- gut)E.g: Hydra, Millepora (coral), Aurelia (jelly- fish),
Rhizostoma, Fungia (mushroom coral) etc.
·
Phylum 3 Ctenophora (ktenos-comb,
phora- carrying)E.g: Pleurobrachia (comb jelly), Cestum (Venu’s girdle), etc.
·
Phylum 4 Platyhelminthes (platys-flat,
helmins- worm; Flatworms) E.g: Planaria, Fasciola,Schistosoma (blood- fluke),
Taenia solium (pork tape worm) etc.
·
Phylum 5 Nematoda E.g: Ascaris
(round- worm), Wucheria bancrofti (filarial worm), Enterobius (pinworm of
human) etc.
·
Phylum 6 Annelida ( annelus- a
ring; segmented worms ) E.g: Nereis (sand worm), Aphrodite (sea mouse),
Pheretima (earthworm), Hirudinaria (Indian cattle leech) etc.
·
Phylum7 Arthropoda (arthros-
jointed; podos- foot; jointed- legged animals) E.g: Peripatus, Cancer (true
cab), Scolopendra (Centipede), Anopheles (mosquito), Pieries (butterfly) etc.
·
Phylum 8 Mollusca (molluscus-
soft) E.g: Pila (apple nail), Helix (garden snail), Octopus (devil-fish) etc.
·
Phyllum 9 Echinodermata ( echinos-
spiny or hedge hog, derma- skin; spiny skinned animals) E.g: Antedon (feather
star), Cucumaria (sea cucumber), Asterias (star- fish or sea star) etc.
·
Phyllum 10 Chordata ( chorda-
string) It is the most advanced goup. It consists of reptiles, Amphibians,
Aves, Mammalia etc.
No comments:
Post a Comment