Animal Kingdom — NEET UG practice

Checking statement A: Platyhelminthes (flatworms) have a digestive system with only one opening (mouth), so undigested waste and food intake share the same opening. This makes the digestive system incomplete, so statement A is correct.

Checking statement B: Radial symmetry, not bilateral symmetry, is the feature seen in adult echinoderms; bilateral symmetry is instead seen in their larval stage. So, statement B is incorrect.

Checking statement C: Members of Aschelminthes (roundworms) possess a body cavity called a pseudocoelom, which is not fully lined by mesoderm. So, statement C is correct.

Checking statement D: In class Chondrichthyes (cartilaginous fishes like sharks), the notochord does persist throughout life, since it is never fully replaced by a vertebral column. So, statement D is correct.

Checking statement E: Reptiles are cold-blooded (poikilothermic) animals, meaning their body temperature changes with the surroundings rather than staying constant. So, statement E is incorrect.

Conclusion: The incorrect statements are B and E. Hence, the answer is option B.

Checking option A (Struthio): This is the ostrich, which is flightless, but its forelimbs are small and used mainly for balance while running — not modified into paddles for swimming.

Checking option B (Neophron): This is a vulture, which is a strong flier, so it doesn't match "flightless" at all.

Checking option D (Psittacula): This is a parrot, another flying bird, so it also does not fit the description.

Checking option C (Aptenodytes): This is the penguin, a bird that cannot fly, and whose forelimbs have evolved into flipper-like (paddle-shaped) structures that make it an excellent swimmer.

Conclusion: Only the penguin matches both being flightless and having paddle-like forelimbs for swimming. Hence, the answer is option C, Aptenodytes.

Understanding radial symmetry: A body is said to be radially symmetrical if any plane passing through the central axis divides it into two identical (mirror-image) halves — think of how a wheel looks the same no matter which diameter you cut it along. This matches exactly what Statement I describes, so Statement I is correct.

Recalling body symmetry in Echinodermata: Echinoderms (like starfish and sea urchins) are known for their radial symmetry as adults — their body parts are arranged around a central point.

Checking the larval stage: However, the larvae of echinoderms do not show this pattern. They are bilaterally symmetrical, meaning only one plane (through the midline) divides them into equal left and right halves. Radial symmetry appears only after metamorphosis into the adult form.

Evaluating Statement II: Since the larvae are bilateral and not radial, the claim that "both adults and larvae are radially symmetrical" is false. Hence, Statement II is incorrect.

Conclusion: Statement I is correct, but Statement II is incorrect. Hence, the answer is option D.