In the phosphorus cycle, phosphate becomes available by weathering of rocks first to

Consider the following statements concerning food chains.
$I$. Removal of $80\; \%$ tigers from an area resulted in greatly increased growth of vegetation.
$II.$ Removal of most of the carnivores resulted in an increased population of deers.
$III.$ The length of food chains is generally limited to $3$ to $4$ trophic levels due to energy loss.
$IV.$ The length of food chains may vary from $2$ to $8$ trophic levels.
Which two of the above statements are correct?

$A$: The soil of tropical rain forests has a low base content.
$R$: Such soil shows less percolation and leaching.

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

Match the following columns:

Column-$I$	Column-$II$
$(a)$ Earthworm	$(i)$ Pioneer species
$(b)$ Succession	$(ii)$ Detritivores
$(c)$ Ecosystem service	$(iii)$ Birth rate
$(d)$ Population growth	$(iv)$ Pollination

Match the following columns:

Column-$I$	Column-$II$
$(i)$ Ecosystem	$(P)$ Bacteria,Fungi
$(ii)$ Food chain	$(Q)$ Nutrient cycling
$(iii)$ Birds	$(R)$ Primary consumer
$(iv)$ Decomposers	$(S)$ Deer