Which one of the following is a characteristic feature of a cropland ecosystem?

Which of the following has the largest population in a food chain?

Maximum contribution of $O_2$ is from

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.

Carbon constitutes . . . . . . of dry weight of organisms and . . . . . . percentage is dissolved in oceans out of total global carbon.

If less light falls on the pond's surface,what is the most likely consequence for the fish population?