Match Column-$I$ with Column-$II$ and select the correct option.

Column-$I$	Column-$II$
$(a)$ Mutualism	$(i)$ Potent force of organic evolution
$(b)$ Orchid	$(ii)$ Negative interaction
$(c)$ Parasitism	$(iii)$ Beneficial interaction
$(d)$ Competition	$(iv)$ No harm to the host

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

$A$: Different ecotypes of a species,despite being genotypically different,are interfertile.
$R$: They are locally natural selections from a pool of genetic variations found in the gene pool of a species.

Consider the following statements $(A-D)$ each with one or two blanks.
$(A)$ Bears go into $ . . . . . . (1) . . . . . . $ during winter to $ . . . . . . (2) . . . . . . $ cold weather.
$(B)$ $A$ conical age pyramid with a broad base represents $ . . . . . . (3) . . . . . . $ human population.
$(C)$ $A$ wasp pollinating a fig flower is an example of $ . . . . . . (4) . . . . . . $.
$(D)$ An area with high levels of species richness is known as $ . . . . . . (5) . . . . . . $.
Which one of the following options gives the correct fill-ups for the respective blank numbers from $(1)$ to $(5)$ in the statements?

Match the ecological hierarchy given in Column-$I$ with their explanation in Column-$II$. Choose the correct answer from options given below.

Column-$I$	Column-$II$
$a$. Organism	$i$. Flora and fauna of a specific climatic zone.
$b$. Population	$ii$. Populations of different species of an area.
$c$. Community	$iii$. Organisms of same kind inhabiting an area.
$d$. Biome	$iv$. Basic unit of hierarchy.

The significance of the study of population is to understand: