What is Notochord? What is its Function? MCQ - Practice Questions with Answers

Segmentation: 

• It refers to the division of the body into numerous transverse segments called metameres. These metameres function in coordination with each other. 
• The segmentation is also called as metamerism. 

Based on metamerism, animals can be of following types:

Unsegmented: 

• These animals do not show any segmentation, e.g., aschelminthes.

Segmented: 

• The body is divided into segments not only externally but also internally. 
• There occurs septation along the inner body walls that divide the organs internally. 
• It is called true segmentation, as seen in annelids.

Pseudosegmentation: 

• The body is divided into segments only externally. 
• Each such segment is capable of growing individually, as seen in tapeworms.

Notochord: 

• It is the rod-like cartilaginous structure which is present dorsally during the development of embryo in animals. 
• It is derived from the mesoderm. 
• Those animals that do not possess notochord at any stage of their life cycles are called non-chordates. For example, sponges, coelenterates, platyhelminthes etc.
• Those animals that possess the notochord either throughout or at any stage of their life cycles are called chordates. For example, hemichordates, urochordates etc.
• In some chordates, the notochord is replaced by a bony vertebral column. Such animals are called vertebrates. For example, mammals.