Select the set of fishes which belong to the class Osteichthyes:

Core Logic

Let's analyze the given characteristics:

• Cartilaginous endoskeleton.
• Ectoparasites on some fishes, possessing a circular, sucking mouth without jaws (Agnatha).
• Devoid of scales and paired fins.
• Bear 6-15 pairs of gill slits (the prompt specifically noted 7 pairs).

These are the exact defining features of Class Cyclostomata. The classic example of this class is Petromyzon (Lamprey).

Step 1: Analyzing Other Options

• Scoliodon (Dogfish) has jaws, paired fins, and placoid scales.
• Exocoetus (Flying fish) is a bony fish (Osteichthyes) with jaws and scales.
• Branchiostoma is a cephalochordate (lancelet), not an ectoparasite with a circular sucking mouth.

Step 2: Final Conclusion

The described animal is Petromyzon sp.

Pattern Recognition

Keywords "circular sucking mouth", "ectoparasite on fishes", and "no scales/paired fins" instantly point to Cyclostomes. Petromyzon and Myxine are the two examples.

Chapter Mix

Class 11 Biology: Animal Kingdom

Core Logic

Let's identify the scientific names from Class Aves:

• Neophron is a vulture (capable of flight).
• Psittacula is a parrot (capable of flight).
• Struthio is an ostrich. It is a flightless bird, but its forelimbs are small and used for balance while running, not for swimming.
• Aptenodytes is the genus for the Emperor Penguin. Penguins are flightless birds whose forelimbs are structurally modified into flippers (paddle-like) specifically for swimming.

Step 1: Final Conclusion

The bird that matches the description is Aptenodytes.

Pattern Recognition

Bird + Swimming forelimbs = Penguin. Scientific name for Penguin in NCERT = Aptenodytes.

Chapter Mix

Class 11 Biology: Animal Kingdom

Core Logic

(A) arrow$\rightarrow$ correct arrow$\rightarrow$ Platyhelminthes have an incomplete digestive system. (B) arrow$\rightarrow$ incorrect arrow$\rightarrow$ Bilateral symmetry is a characteristic feature of larvae of echinoderms. In adult echinoderms, radial symmetry is seen. (C) arrow$\rightarrow$ correct arrow$\rightarrow$ Aschelminthes are characterised by the presence of a pseudocoelom. (D) arrow$\rightarrow$ correct arrow$\rightarrow$ Notochord is persistent throughout life in the Chondrichthyes. (E) arrow$\rightarrow$ incorrect arrow$\rightarrow$ Reptiles are cold-blooded (poikilothermic) organisms and thus, they cannot maintain a constant body temperature.

Step 1: Final Conclusion

Thus, the incorrect statements are (B) and (E) only.

Pattern Recognition

Adult echinoderms = radial (pentamerous). Reptiles = cold-blooded (not constant temp).

Chapter Mix

Class 11 Biology: Animal Kingdom