Which of the following is responsible for the high biomass in an aquatic ecosystem?

Identify the correct statements from the following:
$(1)$ Succession occurring in dry areas is called xerarch succession.
$(2)$ The stage where plants can survive in open conditions throughout the year is the herb stage.
$(3)$ Ecological succession leads to a decrease in the net primary productivity of the community.
$(4)$ Primary succession takes an average of $1000$ years to complete.

Which stage is represented by the given figure?

Differentiate between Production and Decomposition.

Identify the group of herbivores from the following that are included as primary consumers in an ecosystem.

Identify $X$ from the figure: