Q21. The phylum Porifera is characterized by which of the following?
a) Presence of a true coelom
b) Radial symmetry
c) Segmented bodies
d) Pores and canals for water circulation
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Correct Answer: d) Pores and canals for water circulation
Explanation: Poriferans, or sponges, have a porous body structure with numerous openings called pores and a system of canals that allow water to circulate through their bodies. This aids in filter feeding and gas exchange.
Q22. Members of the phylum Annelida are commonly known as:
a) Roundworms
b) Flatworms
c) Segmented worms
d) Cnidarians
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Correct Answer: c) Segmented worms
Explanation: Annelids, such as earthworms and leeches, are characterized by their segmented bodies, with each segment containing a repetition of certain structures. They exhibit a high degree of specialization within each segment.
Q23. The phylum Mollusca includes organisms with which of the following features?
a) Segmented bodies and jointed appendages
b) Radial symmetry and tentacles
c) Soft bodies and often possess a hard shell
d) Spiny skin and water vascular system
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Correct Answer: c) Soft bodies and often possess a hard shell
Explanation: Mollusks are soft-bodied animals that often possess a hard external shell for protection. They exhibit a wide range of body forms and lifestyles, including gastropods, bivalves, and cephalopods.
Q24. Which of the following is a characteristic feature of the phylum Arthropoda?
a) Presence of a water vascular system
b) Soft bodies and often possess a hard shell
c) Radial symmetry
d) Segmented bodies and jointed appendages
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Correct Answer: d) Segmented bodies and jointed appendages
Explanation: Arthropods, such as insects, spiders, crustaceans, and centipedes, are characterized by their segmented bodies and jointed appendages, which provide them with mobility and flexibility in movement.
Q25. Organisms belonging to the phylum Echinodermata typically exhibit which type of symmetry?
a) Bilateral symmetry
b) Radial symmetry
c) Asymmetry
d) Spherical symmetry
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Correct Answer: b) Radial symmetry
Explanation: Echinoderms, such as sea stars and sea urchins, exhibit radial symmetry, meaning their body parts are arranged around a central axis, allowing them to access food and respond to stimuli from various directions.
Q26. The phylum Nematoda includes organisms that are commonly known as:
a) Flatworms
b) Roundworms
c) Segmented worms
d) Cnidarians
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Correct Answer: b) Roundworms
Explanation: Nematodes, or roundworms, are unsegmented worms with cylindrical bodies. They are found in a wide range of habitats and play various roles as decomposers, parasites, and predators.
Q27. Members of the phylum Platyhelminthes are commonly known as:
a) Flatworms
b) Roundworms
c) Segmented worms
d) Cnidarians
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Correct Answer: a) Flatworms
Explanation: Platyhelminths, or flatworms, are characterized by their flattened, ribbon-like bodies. They exhibit bilateral symmetry and include both free-living and parasitic species.
Q28. The phylum Cnidaria includes organisms that possess specialized stinging cells called:
a) Nematocysts
b) Setae
c) Tentacles
d) Cnidocytes
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Correct Answer: d) Cnidocytes
Explanation: Cnidocytes are specialized cells found in cnidarians, such as jellyfish and sea anemones, that contain stinging organelles called nematocysts. These cells are used for defense and capturing prey.
Q29. Which of the following phyla includes organisms that often possess a notochord and a dorsal hollow nerve cord?
a) Echinodermata
b) Chordata
c) Mollusca
d) Arthropoda
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Correct Answer: b) Chordata
Explanation: Chordates are characterized by the presence of a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail at some stage of their development. This phylum includes vertebrates and some invertebrate groups.
Q30. The phylum Porifera includes organisms commonly known as:
a) Sponges
b) Jellyfish
c) Sea stars
d) Snails
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Correct Answer: a) Sponges
Explanation: Poriferans, or sponges, are multicellular organisms characterized by a porous body structure. They are filter feeders, drawing in water through pores and capturing food particles within their bodies.