Intracellular vs Extracellular Digestion—NEET Biology

Correct answer: A — S1, S3 and S5 only

Let's evaluate each statement: S1: Correct. Cnidarians exhibit tissue level of organisation and are diploblastic. They have a central gastro-vascular cavity with a single opening, mouth on hypostome. (NCERT, page 41, Section 4.2.2). S2: Incorrect. The undifferentiated layer present between the external ectoderm and internal endoderm in diploblastic animals like cnidarians is called mesoglea, not composed of mesodermal cells. Mesoderm is the third germinal layer found in triploblastic animals. (NCERT, page 38, Section 4.1.3). S3: Correct. Cnidoblasts (or cnidocytes) contain stinging capsules or nematocysts and are used for anchorage, defense, and for the capture of prey. (NCERT, page 41, Section 4.2.2). S4: Incorrect. Cnidarians are aquatic and *mostly* marine, not *all* exclusively marine (e.g., Hydra is freshwater). Also, only *those* cnidarians which exist in both polyp and medusa forms exhibit alternation of generations (metagenesis), not *all* members. (NCERT, page 41, Section 4.2.2). S5: Correct. Digestion in cnidarians is both extracellular (in the gastrovascular cavity) and intracellular (within the cells). (NCERT, page 41, Section 4.2.2). Therefore, statements S1, S3, and S5 are correct.