Animal Kingdom


   
 
Phylum Coelenterata
 
Radially symmetrical, diploblastic multicellular animals with a tissue grade of organisation.
 
Aquatic, freshwater or marine solitary or colonial forms which may be free swimming or sedentary.
 
Body has a mouth at the oral end which leads into a spacious cavity called gastrovascular cavity or coelenteron.
 
Presence of long, hollow structures called tentacles used for locomotion and food capturing.
 
Presence of peculiar type of cells called cnidoblasts, nematocysts or stinging cells in the ectoderm, especially in the tentacles, used for offence and defence.
 
Digestion is both intracellular and extracellular.
 
Respiration and excretion by simple diffusion.
 
Presence of a network of nerves spread all over the body.
 
Many forms exhibit polymorphism, wherein different types of individuals are present in a colony for different functions. These individuals are called Zooids.
 
Reproduction asexually (external budding) or sexually (formation of gametes).
 
 
    fig. 10.7 - Examples of Coelenterata
 
The phylum is divided into three classes
 
 
 
                    fig. 10.8 - Anatomy of Hydra
 
 
     
   
Get unlimited tutoring in Math, English, Physics, Chemistry, Biology, Algebra, Geometry and all other subjects at $99.99 per month!