Identify the likely organisms $(1), (2), (3)$ and $(4)$ in the food web shown below.

Zooplanktonic forms are

Some of the stages in the hydrarch succession are labelled as:
$I.$ Marsh meadow stage
$II.$ Reed swamp stage
$III.$ Submerged plant stage
$IV.$ Phytoplankton stage
$V.$ Submerged free floating plant stage
Identify the choice that represents the correct sequence of these stages.

Carnivores are

How much carbon is dissolved in the oceans (in $; \%$)?

Choose the correct sequence of True $(T)$ and False $(F)$ statements:
$(1)$ Zooplanktons are primary producers in an aquatic ecosystem.
$(2)$ Decomposition is largely an oxygen-requiring process.
$(3)$ In a natural ecosystem, fishes, wolf, etc., are carnivores.
$(4)$ The amount of energy decreases at each successive trophic level.