Animal Classification: Fundamental Body Features — NEET Biology
📚 Practice ConceptInspite of differences in structure and form of different animals, there are fundamental features common to various individuals in relation to the arrangement of cells, body symmetry, nature of coelom, patterns of digestive, circulatory or reproductive systems. These features are used as the basis of animal classification and some of them are discussed here.
Which of the following statements correctly describes the fundamental features of animal classification? S1. In diploblastic animals, an undifferentiated layer called mesoglea is present between the ectoderm and endoderm, as seen in Coelenterates. S2. Platyhelminthes exhibit organ level of organization, bilateral symmetry, and are acoelomate, lacking any body cavity. S3. Aschelminthes are pseudocoelomates with a complete digestive system and organ-system level of organization. S4. All coelomates, such as Annelids and Molluscs, possess a body cavity lined by mesoderm and invariably exhibit metameric segmentation. S5. Notochord is a mesodermally derived, rod-like structure present in all Chordates throughout their embryonic development, and in some, persists throughout life.
View solution & NCERT explanation
Correct answer: C — S1, S2, S3 and S5
Let's evaluate each statement based on NCERT: S1. Correct. Diploblastic animals (like coelenterates) have two embryonic layers, with mesoglea in between. (NCERT: "Animals in which the cells are arranged in two embryonic layers... called diploblastic animals, e.g., coelenterates. An undifferentiated layer, mesoglea, is present in between the ectoderm and the endoderm.") S2. Correct. Platyhelminthes are indeed characterized by organ level organization, bilateral symmetry, and are acoelomate. (NCERT: "Flatworms are bilaterally symmetrical, triploblastic and acoelomate animals with organ level of organisation.") S3. Correct. Aschelminthes are pseudocoelomates, have organ-system level of organization, and a complete digestive system. (NCERT: "Roundworms have organ-system level of body organisation. They are bilaterally symmetrical, triploblastic and pseudocoelomate animals. Alimentary canal is complete...") S4. Not correct. While coelomates possess a body cavity lined by mesoderm, the statement that *all* coelomates invariably exhibit metameric segmentation is false. For example, molluscs and echinoderms are coelomates but do not show metameric segmentation. (NCERT: "Animals possessing coelom are called coelomates, e.g., annelids, molluscs, arthropods... In some animals, the body is externally and internally divided into segments... metameric segmentation and the phenomenon is known as metamerism.") S5. Correct. The notochord is a mesodermally derived structure characteristic of Chordates during embryonic development, and in some protochordates, it persists throughout life. (NCERT: "Notochord is a mesodermally derived rod-like structure formed on the dorsal side during embryonic development in some animals. Animals with notochord are called chordates... In Urochordata, notochord is present only in larval tail, while in Cephalochordata, it extends from head to tail region and is persistent throughout their life.") Therefore, statements S1, S2, S3, and S5 are correct. The final answer is C.
What does NCERT say about Inspite differences structure and?
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Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.