kingdom Animalia. (PART 02)


Two subkingdoms,

                1.Sub kingdom Parazoa.

                2.Sub kingdom Eumetazoa.


Sub kingdom Parazoa


Parazoa lacks definite shape & symmetry.

They haven't tissues & organs.


 Sub Kingdom Parazoa have 2 phyla,

 1.Placozoa

 2.Porifera 


 1.Placozoa

    Formed by a single layer.

    No well-developed inner layers.

 2.Porifera 

    Formed by a single layer


Sub Kingdom Eumetazoa.


Eumetazoa has definite shape & symmetry.

The lowest eumetazoans body is formed of cells organized into tissues.

The group of tissue formed organs, group of organs formed the organ system.

Organ systems differ in their body shape & size.

Organ & organ system have functions

such as,

           1.digestion.

           2.circulation.

           3.respiration.

           4.excreation.

           5.reproduction.

Sub Kingdom Eumetazoa have 35 phyla.

Divide into 2 groups by body symmetry & number of germ layers,

           1. diploblastic animals/radial symmetry

           2. triploblastic animals/bilateral symmetry

1st group includes cnidaria, Ctenophora.

2nd group all other Eumetzoans.


Evolution of head region called cephalization.

With the increase in complexity and increase the size of animal 2 features developed,

There are,

       1.body cavity

       2.coelom & metameric segmentation 


pseudocoelom- body cavity not completely lined by mesoderm 

These animals are pseudocoelomates.

Three layered Pseudocoelom



Annelids - 1st true coelomates / completely surrounded by mesoderm.

With the development of the coelom,

        Animal body cavity divided into segments that visible externally & internally. Each segment carried organs or organs system.

 The evolution of such segmentation in an animal is referred to as  segmentation(metameric segmentation)

eg: Neris

Each segment have organs,

Nephridia
parapodia
gonads...etc


Formation of tagma called tagmatization.

Ex: Tagma of the insects(head,thorax,abdomen)