Sponges belong to which one among the following phylum ?
- A.Porifera
- B.Platyhelminthes
- C.Cnidaria
- D.Annelida
Correct answer
Explanation
The correct answer is A, Porifera. Sponges are the members of phylum Porifera, a name that means "pore bearers", because their bodies are full of tiny pores called ostia. Sponges are the simplest multicellular animals. They are mostly marine, live fixed to rocks, and have a cellular level of organisation with no true tissues or organs. Water enters through the ostia, passes into a central cavity called the spongocoel and leaves through a large opening, the osculum. This water canal system brings in food and oxygen and carries away waste. Collar cells, or choanocytes, line the canals and drive the current. The body is supported by spicules or spongin fibres. Examples are Sycon, Spongilla and Euspongia, the bath sponge. Option B is wrong because Platyhelminthes are the flatworms, such as tapeworm and liver fluke. Option C is wrong because Cnidaria, such as Hydra, jellyfish and corals, have stinging cells. Option D is wrong because Annelida are segmented worms such as the earthworm and leech. Exam tip: Porifera means pores and a water canal system; Cnidaria means stinging cnidoblasts.
Practice Questions
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- A.refraction
- B.reflection
- C.polarization
- D.dispersion
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- A.The packet will float in both water and liquid B.
- B.The packet will sink in both water and liquid B.
- C.The packet will sink in water but will float in liquid B.
- D.The packet will float in water and sink in liquid B.
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- A.between pole (P) and the focus (F), behind the mirror
- B.between the focus (F) and infinity, behind the mirror
- C.between the pole (P) and the infinity, in front of the mirror
- D.at the focus (F), behind the mirror
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- A.double
- B.half
- C.four times
- D.one fourth
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