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प्रश्न
Write short note on protochordates.
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उत्तर
Protochordates belong to phylum Chordata. They are further subdivided into two subphylums:
(i) Urochordata
They are bag-like, sessile, soft-bodied, non-metameric animals. In these organisms, the notochord is present only in the tail of free-living tadpole-like larva. The dorsal tubular nerve chord also degenerates in the form of small ganglion in the adult. The only chordate character present in the adult form are the numerous gill slits. Urochordates are hermaphrodites. Example: Herdmania.
(ii) Cephalochordata
They are fish-like, metamerically segmented, headless and coelomate animals. In these organisms, notochord and nerve cord extend throughout the length of the body. The notochord, nerve chord and pharyngeal gill slits are retained throughout life. Sexes are separate in Cephalochordates. Example: Amphioxus.
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संबंधित प्रश्न
How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?
Match the following:
| Column I | Column II | ||
| (a) | Operculum | (i) | Ctenophora |
| (b) | Parapodia | (ii) | Mollusca |
| (c) | Scales | (iii) | Porifera |
| (d) | Comb plates | (iv) | Reptilia |
| (e) | Radula | (v) | Annelida |
| (f) | Hairs | (vi) | Cyclostomata and Chondrichthyes |
| (g) | Choanocytes | (vii) | Mammalia |
| (h) | Gill slits | (viii) | Osteichthyes |
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