Answer: Two layers: ectoderm and endoderm.
- A One layer with no distinction
- B Two layers: ectoderm and endoderm
- C Three layers: ectoderm, mesoderm, and endoderm
- D Four distinct layers
Correct answer: B. Two layers: ectoderm and endoderm
Explanation: Diploblastic animals (Cnidaria, Ctenophora) have two embryonic germ layers, ectoderm and endoderm, with an undifferentiated mesoglea in between.
Moving across the animal phyla, body organisation becomes progressively more complex: from no symmetry and cellular organisation (Porifera) through radial/diploblastic (Cnidaria), bilateral/acoelomate (Platyhelminthes), pseudocoelomate (Nematoda), to a true coelom with full organ systems (Annelida and beyond).
Concept context
Phylum-level classification of the animal kingdom from Porifera to Chordata, based on body symmetry, coelom, and segmentation. One of the most example-heavy chapters for NEET.