Identify the possible link “$A$” in the following food chain.

Plant $→$ Insect $→$ Frog $→$ “$A$” $→$ Eagle

Secondary producers are

A plant being eaten by a herbivorous which in turn is eaten by a carnivorous makes

$A$ : In secondary productivity, no new organic matter is formed.

$R$ : It is only utilisation of part of food manufactured by primary producers in building of consumer biomass.

A rat feeding upon potato tuber is