Q21. The phylum Nematoda includes organisms commonly known as:
a) Flatworms
b) Roundworms
c) Segmented worms
d) Sponges
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Correct Answer: b) Roundworms
Explanation: Nematodes, or roundworms, are unsegmented worms with a cylindrical body shape. They are found in various environments and can be parasitic or free-living.
Q22. Which of the following is not a class of mollusks?
a) Gastropoda
b) Cephalopoda
c) Bivalvia
d) Arachnida
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Correct Answer: d) Arachnida
Explanation: Arachnids belong to the class Arachnida within the phylum Arthropoda. Gastropoda, Cephalopoda, and Bivalvia are classes within the phylum Mollusca.
Q23. An example of an animal belonging to the class Osteichthyes is:
a) Shark
b) Jellyfish
c) Goldfish
d) Starfish
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Correct Answer: c) Goldfish
Explanation: Osteichthyes, or bony fish, include species like goldfish, trout, and tuna. Sharks belong to the class Chondrichthyes, jellyfish are cnidarians, and starfish are echinoderms.
Q24. The phylum Arthropoda includes organisms with:
a) Segmented bodies and jointed appendages
b) Radial symmetry
c) A notochord
d) A closed circulatory system
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Correct Answer: a) Segmented bodies and jointed appendages
Explanation: Arthropods have segmented bodies and jointed appendages, which facilitate movement and diverse functions. They do not exhibit radial symmetry, possess a notochord, or have a closed circulatory system.
Q25. An example of an animal belonging to the class Chondrichthyes is:
a) Goldfish
b) Shark
c) Frog
d) Crocodile
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Correct Answer: b) Shark
Explanation: Chondrichthyes, or cartilaginous fish, include sharks, rays, and skates. Goldfish are bony fish (Osteichthyes), while frogs and crocodiles belong to different classes altogether.
Q26. The exoskeleton of arthropods is primarily composed of:
a) Calcium carbonate
b) Chitin
c) Keratin
d) Collagen
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Correct Answer: b) Chitin
Explanation: The exoskeleton of arthropods, including insects, crustaceans, and arachnids, is primarily composed of chitin, a tough polysaccharide providing protection and support.
Q27. An example of an animal with a coelom is:
a) Earthworm
b) Jellyfish
c) Sponge
d) Hydra
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Correct Answer: a) Earthworm
Explanation: Earthworms have a true body cavity called a coelom, which contains their internal organs. Jellyfish, sponges, and hydras lack a coelom.
Q28. The class Aves includes organisms characterized by:
a) Hollow bones and feathers
b) Endoskeleton made of cartilage
c) Cold-blooded metabolism
d) External fertilization
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Correct Answer: a) Hollow bones and feathers
Explanation: Birds, belonging to the class Aves, have hollow bones for reduced weight and feathers for flight, insulation, and display. They are endothermic and typically undergo internal fertilization.
Q29. An example of an animal with an exoskeleton is:
a) Fish
b) Crab
c) Frog
d) Bird
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Correct Answer: b) Crab
Explanation: Crabs, along with other arthropods like insects and spiders, have an exoskeleton, which provides protection and support. Fish, frogs, and birds have internal skeletons.
Q30. The respiratory system of birds primarily involves:
a) Gills
b) Lungs
c) Tracheae
d) Spiracles
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Correct Answer: b) Lungs
Explanation: Birds have lungs for respiration, similar to mammals, but with additional air sacs that aid in efficient gas exchange during both inhalation and exhalation. Gills, tracheae, and spiracles are respiratory structures found in other animal groups.