The given human population age pyramid represents..........

$X$ - In deep-sea hydrothermal vents,the average temperature is between $25^{\circ}C$ to $30^{\circ}C$.
$Y$ - Reptiles and amphibians are eurythermal.

According to the $1991$ census,the maximum percentage of population increase was in which state?

Match the columns:

Column-$I$	Column-$II$
$(a)$ Earthworm	$(i)$ Birth-rate
$(b)$ Succession	$(ii)$ Pioneer species
$(c)$ Population rise	$(iii)$ Pollination
$(d)$ Ecological services	$(iv)$ Saprotrophs

The figure given below is a diagrammatic representation of the response of organisms to abiotic factors. What do $(a)$,$(b)$,and $(c)$ represent respectively?
$(a)$ $(b)$ $(c)$

Which of the following levels is not conceptual in terms of size?