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Which one of the following statements about all the four of $Spongilla$, Leech, Dolphin and Penguin is correct?
A
All are bilaterally symmetrical
B
Penguin is homoiothermic while the remaining three are poikilothermic
C
Leech is a fresh water form while all others are marine
D
$Spongilla$ has special collared cells called choanocytes, not found in the remaining three
Detailed Solution
$Spongilla$ is a fresh water sponge (phylum Porifera); sponges have collar cells or choanocytes lining the spongocoel and canals. Choanocytes are not found in the leech (Annelida), dolphin (Mammalia) or penguin (Aves). This statement is correct.
Sponges are mostly asymmetrical, so all four are not bilaterally symmetrical.
The dolphin is a mammal and, like the penguin (a bird), is homoiothermic; so the penguin is not the only warm-blooded one.
$Spongilla$ is a fresh water form, not marine, so the statement about the leech alone being a fresh water form is wrong.
Hence the correct statement is that $Spongilla$ has choanocytes, which are absent in the remaining three.
Sponges are mostly asymmetrical, so all four are not bilaterally symmetrical.
The dolphin is a mammal and, like the penguin (a bird), is homoiothermic; so the penguin is not the only warm-blooded one.
$Spongilla$ is a fresh water form, not marine, so the statement about the leech alone being a fresh water form is wrong.
Hence the correct statement is that $Spongilla$ has choanocytes, which are absent in the remaining three.