Question

In which of the group brain box is absent?
a) cyclostomata b) pisces c) amphibja d) protochordata

Answer 1

i think ur answer is (d) protochordeta .
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coz there is absence of heart in protochordeta

Answer 2

d) protochordata is the answer.



Your explanation
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The Protochordata or Prochorda are simpler forms of the chordate animals in which the notochord is wholly or partially formed and the vertebral column and skull are lacking (hence Acrania). This division includes a heterogeneous (polyphyletic) group of animals of the phylum Chordata, most of which are fairly related to the vertebrates but none possesses the full complement of vertebrate characters.