Organisms of which of the following phylum are called sponges ?
- A.Coelenterata
- B.Platyhelminthes
- C.Porifera
- D.Echinodermata
Correct answer
Explanation
The correct answer is C, Porifera. Sponges belong to the phylum Porifera, a name that means "pore bearers", because their bodies are full of tiny pores.
Porifera are the simplest multicellular animals. They have no true tissues or organs and live fixed to rocks, mostly in the sea. Water enters through pores called ostia, flows through a central cavity and leaves through a large opening called the osculum, bringing food and oxygen. Special collar cells, the choanocytes, keep this water current moving. The body is supported by spicules or by a network of spongin fibres; the bath sponge Spongia is an example.
A is wrong because Coelenterata (Cnidaria) are animals such as Hydra, jellyfish and corals, which have stinging cells.
B is wrong because Platyhelminthes are the flatworms, such as the tapeworm and the liver fluke.
D is wrong because Echinodermata are spiny-skinned sea animals such as the starfish and the sea urchin.
Exam tip: Porifera means sponges with pores and canals; Cnidaria means stinging cells; Echinodermata means spiny skin.
Practice Questions
View allWhich of the following statements about a fluid at rest in a cup is/are correct? 1. Pressure is same at all the points in the fluid 2. Pressure is exerted on the walls. 3. Pressure exists everywhere in the fluid. Select the correct answer using the code given below :
- A.1 and 2 only
- B.2 and 3 only
- C.1 only
- D.1, 2 and 3
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A fluid at rest presses on the walls and has pressure at every point, but that pressure is not the same at all depths.
Read the full explanation →The absolute zero temperature is 0 Kelvin. In °C unit, which one of the following is the absolute zero temperature?
- A.0 °C
- B.-100 °C
- C.-273.15 °C
- D.-173.15 °C
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Zero on the Kelvin scale lies 273.15 degrees below the freezing point of water. The Kelvin and Celsius scales have degrees of the same size, so T(K) = t(°C) + 273.15.
Read the full explanation →Dinitrogen (N₂) and dioxygen (O₂) are the main constituents of air but they do not react with each other to form oxides of nitrogen because
- A.the reaction requires initiation by a catalyst
- B.oxides of nitrogen are unstable
- C.the reaction is endothermic and requires very high temperature
- D.the stoichiometry of N₂ and O₂ in air is not ideal for the reaction to take place
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Nitrogen and oxygen combine only when a lot of energy is supplied. The nitrogen molecule is held by a very strong triple bond, so breaking it takes much energy, and the reaction N₂ + O₂ → 2NO absorbs heat.
Read the full explanation →Hydrogenation of vegetable oils using nickel catalyst is an example of
- A.Substitution reaction.
- B.Elimination reaction.
- C.Addition reaction.
- D.Free-radical polymerization.
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Hydrogen adds across the carbon–carbon double bonds of the oil. Vegetable oils are unsaturated: their fatty acid chains contain C=C double bonds, which keep them liquid.
Read the full explanation →A positive charge is moving towards south in a space where magnetic field is pointing in the north direction. The moving charge will experience :
- A.a deflecting force towards north direction.
- B.a deflecting force towards east direction.
- C.a deflecting force towards west direction.
- D.no deflecting force.
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The charge moves exactly opposite to the field, and a magnetic field exerts no force on a charge moving along its line.
Read the full explanation →