What is the approximate amount of carbon fixed in the biosphere annually through photosynthesis?

Observe the given chart and identify what it represents.

Give scientific reasons: Even though plants are autotrophic,they cannot live alone.

Given below are four statements $(a-d)$ each with one or two blanks. Select the option which correctly fills the blanks in two statements.
$(a)$ Ecological succession is a ...$(i)$... and fairly predictable change in the ...$(ii)$... of a given area.
$(b)$ In ecological succession,the entire sequence of communities that successively change in a given area is called ...$(i)$....
$(c)$ Primary succession occurs on ...$(i)$....
$(d)$ Secondary succession is ...$(i)$... than primary succession.

Read the following statements carefully and answer the question given below:
$(1)$ $NPP = GPP - R$
$(2)$ Productivity of an ecosystem can be measured in $g/m^2/yr$ or $kcal/m^2/day$.
$(3)$ The total amount of energy produced by all producers in an ecosystem is called Gross Primary Productivity $(GPP)$.
$(4)$ The net primary productivity of the oceans is $55$ billion tons.
State the number of correct statements.

Biogeochemical cycles can be traced in