Identify the possible link $A$ in the following food chain.
Plant $\rightarrow$ Insect $\rightarrow$ Frog $\rightarrow$ $A$ $\rightarrow$ Eagle

From the above given features,how many are associated with primary succession?
Features:
$1$. Occur on newly cooled lava
$2$. Faster succession
$3$. Progress to mesic condition
$4$. Occurs on flooded land
$5$. Slower succession
$6$. Changes in flora only

Grassland biome for its maintenance requires

Match the columns:

Column-$I$	Column-$II$
$(i)$ Primary succession	$(i)$ Development of ecosystem
$(ii)$ Ecological succession	$(ii)$ Lichens
$(iii)$ Pioneer species on rocks	$(iii)$ Near to the equilibrium with the environment
$(iv)$ Climax community	$(iv)$ New species on bare environment

Phosphorus of the ocean becomes available to land plants due to:

Identify the possible link '$M$' in the following food chain.
Plant $\rightarrow$ Insect $\rightarrow$ $M$ $\rightarrow$ Snake $\rightarrow$ Eagle