Question 1

How does water move through a sponge?

Accepted Answer

Water enters through many minute pores called ostia, passes through the canal system and the spongocoel, and leaves through the large opening called the osculum. This continuous flow supports internal water transport and gas exchange.

Question 2

Why is Porifera not considered diploblastic?

Accepted Answer

Porifera have a cellular level of organisation rather than true tissues and germ layers. Diploblastic organisation begins in phyla such as Cnidaria and Ctenophora, where ectoderm and endoderm are present with mesoglea between them.

Question 3

What is the difference between a cnidocyte, nematocyst and cnidocil?

Accepted Answer

A cnidocyte is the specialised stinging cell, and a nematocyst is the stinging capsule located inside it. The cnidocil acts as the trigger that controls discharge of the capsule's thread.

Question 4

How do comb rows help a ctenophore move?

Accepted Answer

A ctenophore has eight external longitudinal rows of fused ciliary comb plates. Rhythmic beating of these plates produces locomotion through water, and the rows often show moving rainbow-like colours.

Question 5

What are the main features of Ctenophora?

Accepted Answer

Ctenophora has tissue-level organisation, is diploblastic and is described as radially symmetrical in NCERT. Digestion is extracellular and intracellular, bioluminescence is well marked, sexes are not separate, reproduction is sexual-only, fertilisation is external and development is indirect.

Animal Phyla 3D Lab — Sponge, Hydra & Comb Jelly

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