The planktonic forms are
Autotrophs
Heterotrophs
Chemotrophs
Insectivorous types
$A$ : Detrivores and decomposers hold up a part of nutrients contained in detritus.
$R$ : Immobilised nutrients cannot be available for solubilisation after the death of saprotrophs.
The bacteria which attack dead animals are
The number of individuals of a species in a particular ecosystem at a given time remains constant due to
The aquatic organism that can actively swim at will against the water current is