Which of the following phyla is characterised by radial symmetry, diploblastic organisation and the presence of cnidoblasts?
A{'text': 'Coelenterata', 'label': 'A'}
B{'text': 'Porifera', 'label': 'B'}
C{'text': 'Ctenophora', 'label': 'C'}
D{'text': 'Platyhelminthes', 'label': 'D'}
Answer & Solution
Correct answer: A. {'text': 'Coelenterata', 'label': 'A'}
1. Radial symmetry appears in Coelenterata, Ctenophora and Echinodermata.
2. Diploblastic organisation with ectoderm + endoderm is exclusive to Coelenterata and Ctenophora.
3. Cnidoblasts (cnidocytes containing nematocysts) are diagnostic of Coelenterata (Cnidaria) alone.
4. Ctenophores use ciliated comb plates and lack cnidoblasts.
_Source: NCERT Class 11 Biology, Ch 4 "Animal Kingdom", §4.2.2_
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