In a marine ecosystem,the biomass pyramid is . . . . . . .

The pyramid of numbers in a cropland ecosystem is:

Inverted pyramid of number and inverted pyramid of biomass are respectively seen in.

Following criteria are used for construction of ecological pyramids $EXCEPT$ . . . . . . .

$A$: Ecological pyramid of biomass is generally inverted in the sea.
$R$: Biomass of fishes far exceeds that of phytoplanktons.

To show how many organisms are present at each level of a food chain,ecologists use a model called