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Q51.
The statement "all vertebrates are chordates but all chordates are not vertebrates" is correct because:
[Animal-Kingdom] [class-xi]
Correct option: B [ Vertebrates have a notochord only in the embryonic stage, which is replaced by a vertebral column. ]
Remark: Explanation: All vertebrates are chordates because they possess a notochord during the embryonic period. However, not all chordates are vertebrates because in vertebrates, this notochord is replaced by a bony or cartilaginous vertebral column in the adult, a feature not present in protochordates.
Q52.
Vertebrates that lack jaws belong to the division:
[Animal-Kingdom] [class-xi]
Correct option: D [ Agnatha ]
Remark: Explanation: The subphylum Vertebrata is divided into two divisions: Agnatha (lacks jaw) and Gnathostomata (bears jaw).
Q53.
Class Cyclostomata members are typically:
[Animal-Kingdom] [class-xi]
Correct option: B [ Ectoparasites on some fishes ]
Remark: Explanation: All living members of the class Cyclostomata are ectoparasites, meaning they live on the outside of other fish.
Q54.
Cyclostomes migrate for spawning to:
[Animal-Kingdom] [class-xi]
Correct option: C [ Fresh water ]
Remark: Explanation: Cyclostomes are marine but they migrate to fresh water for spawning (reproduction).
Q55.
The endoskeleton of Chondrichthyes is made of:
[Animal-Kingdom] [class-xi]
Correct option: C [ Cartilage ]
Remark: Explanation: Animals in the class Chondrichthyes, such as sharks and rays, have an endoskeleton made entirely of cartilage.
Q56.
The teeth in Chondrichthyes are modified:
[Animal-Kingdom] [class-xi]
Correct option: C [ Placoid scales ]
Remark: Explanation: The skin of Chondrichthyes is tough and contains minute placoid scales. Their teeth are modified placoid scales.
Q57.
Why must sharks (Chondrichthyes) swim constantly?
[Animal-Kingdom] [class-xi]
Correct option: B [ Due to the absence of an air bladder to avoid sinking ]
Remark: Explanation: Chondrichthyes lack an air bladder, a gas-filled sac that provides buoyancy in bony fish. Therefore, they must swim constantly to avoid sinking.
Q58.
The electric organs of Torpedo and the poison sting of Trygon are features found in which class?
[Animal-Kingdom] [class-xi]
Correct option: B [ Chondrichthyes ]
Remark: Explanation: Some members of Chondrichthyes have specialized organs, such as the electric organs in Torpedo and the poison sting in Trygon.
Q59.
The class that includes both marine and freshwater fishes with a bony endoskeleton is:
[Animal-Kingdom] [class-xi]
Correct option: B [ Osteichthyes ]
Remark: Explanation: The class Osteichthyes includes both marine and freshwater fish that have a bony endoskeleton.
Q60.
The structure that covers the gills in bony fishes is called the:
[Animal-Kingdom] [class-xi]
Correct option: A [ Operculum ]
Remark: Explanation: In bony fishes (Osteichthyes), the four pairs of gills are covered by a gill cover called an operculum on each side.