Long Answer
Medium difficulty • Structured explanation
Question 1
Long FormCompare and contrast the features of Porifera and Coelenterata with reference to their level of organisation, symmetry, digestion, and reproduction.
- Porifera exhibit cellular level of organisation, whereas Coelenterata show tissue level of organisation, representing an evolutionary advancement.
- Sponges are mostly asymmetrical, while coelenterates are radially symmetrical, allowing equal interaction with the environment from all sides.
- Digestion in sponges is exclusively intracellular within choanocytes, whereas in coelenterates digestion is both extracellular (in gastrovascular cavity) and intracellular.
- Sponges are hermaphroditic and reproduce both asexually (fragmentation) and sexually (gamete formation); coelenterates also have no separate sexes but show metagenesis (polyp-medusa alternation of generations) in some forms.
- Sponges have a unique water canal system (ostia-spongocoel-osculum) for nutrition and respiration; coelenterates have a central gastrovascular cavity with a single opening (mouth on hypostome).
- Both phyla are predominantly marine, diploblastic, and lack a true coelom; however, coelenterates possess specialised cnidoblasts with nematocysts for prey capture, a feature absent in sponges.