Coelom is a fluid filled space between the body wall and digestive tract. The presence or absence of body cavity or coelom plays a very important role in the classification of animals.
Animals that possess a fluid filled cavity between body wall and digestive tract are known as coelomates. Annelids, mollusks, echinodermates, and chordates are examples of coelomates. On the other hand, the animals in which the body cavity is not lined by endoderm.
Aschelminthes is an example of pseudocoelomates.
In certain animals, the body cavity is absent. They are known as acoelomates. An example of acoelomates is platyhelminthes.
List - I | List – II | ||
A. | Chondrichthyes | i. | Clarias |
B. | Cyclostomata | ii. | Carcharodon |
C. | Osteichthyes | iii. | Myxine |
D. | Amphibia | iv. | Ichthyophis |
Figures 9.20(a) and (b) refer to the steady flow of a (non-viscous) liquid. Which of the two figures is incorrect ? Why ?
One of the most fundamental forms of classification of animals is the presence or absence of the notochord. Hence, two major groups exist, namely: Chordates and Non-chordates
The subphylum Vertebrata is divided into five classes of vertebrates. These five classes of vertebrates comprise of all the species of animals and have developed vertebral column as well as an internal skeleton.
Other characteristic features of vertebrates are-