Practice MCQs, Assertion–Reason, Match List and Fill in the Blanks from NCERT Class XI Animal Kingdom — answers & concise explanations.
Animal Kingdom - Class-XI: Practice ( MCQs, Assertion-Reason, Match List-I with List-II and Fill in the Blanks) for CBSE and NEET preparation 2026.
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Q51.
The statement "all vertebrates are chordates but all chordates are not vertebrates" is correct because:
[Animal-Kingdom] [class-xi]
All chordates possess a vertebral column.
Vertebrates have a notochord only in the embryonic stage, which is replaced by a vertebral column.
Protochordates are not considered true chordates.
The notochord and vertebral column are the same structure.
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]
Gnathostomata
Tetrapoda
Pisces
Agnatha
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]
Free-swimming predators
Ectoparasites on some fishes
Terrestrial herbivores
Freshwater bottom-dwellers
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]
The deep ocean
Saltwater marshes
Fresh water
Brackish water
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]
Bone
Chitin
Cartilage
Spongin
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]
Ctenoid scales
Cycloid scales
Placoid scales
Bony plates
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]
To find prey
Due to the absence of an air bladder to avoid sinking
To keep their gills ventilated
To regulate their body temperature
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]
Osteichthyes
Chondrichthyes
Cyclostomata
Amphibia
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]
Chondrichthyes
Osteichthyes
Cyclostomata
Amphibia
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]
Operculum
Mantle
Scute
Placoid scale
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.
