Identify the basic components of an ecosystem.

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.

Given below is a simplified model of phosphorus cycling in a terrestrial ecosystem with four blanks $(A-D)$. Identify the blanks.

Some of the nutrient cycles are labelled as below:
$I$. Sulphur cycle
$II$. Phosphorus cycle
$III$. Carbon cycle
$IV$. Nitrogen cycle
Of these,the sedimentary cycle is represented by:

Match Column-$I$ with Column-$II$. Select the option with the correct combination.

$1$. Standing state	$p$. Mass of living material at a given time
$2$. Pioneer species	$q$. Amount of nutrients in the soil at a given time
$3$. Detritivores	$r$. Species that invade a bare area
$4$. Standing crop	$s$. Breakdown detritus into smaller particles

Which of the following contribute to the carbon cycle?