Question

A structure similar to the notochord seen in Hemichordates is known as ----.

• A. somatocord
• B. stomochord
• C. spicocord
• D. neurocord

Answer 1

Answer:

B. stomochord

Phylum Hemichordata:

• Hemichordata was earlier considered as a sub-phylum under phylum Chordata. But now it is placed as a separate phylum under nonchordata. 
• Hemichordates have a rudimentary structure in the collar region called stomochord, a structure similar to notochord
• This phylum consists of a small group of worm-like marine animals . 
• They have organ-system level of organisation
• They are bilaterally symmetrical, triploblastic and coelomates animals.
• The body is cylindrical and is composed of an anterior proboscis, a collar and a long trunk 
• Circulatory system is of open type.
• Respiration takes place through gills.
• Excretory organ is proboscis gland. 
• Sexes are separate.
• Fertilisation is external.
• Development is indirect.
• Examples: Balanoglossus, saccoglossus