What is the primary role of predators in an ecosystem?

Select the $CORRECT$ match:

List-$I$	List-$II$
$i$. Competition	$a$. Tapeworm and man
$ii$. Commensalism	$b$. Lichen
$iii$. Mutualism	$c$. Cattle egret and cattle
$iv$. Parasitism	$d$. Lions and Leopards

. . . . . . $A$ . . . . . . is a potent force in organic evolution. Identify the $A$.

While explaining interspecific interaction of population,$(+)$ sign is assigned for beneficial interaction,$(-)$ sign is assigned for detrimental interaction and $(0)$ for neutral interaction. Which of the following interactions can be assigned $(+)$ for one species and $(-)$ for another species involved in the interaction?

In the early $1920$s,the prickly pear cactus introduced into Australia caused havoc by spreading rapidly into millions of hectares of rangeland. Finally,how was it controlled?

Choose the correct statements regarding population interactions between two species.
$A$. In both parasitism and commensalism, only one species benefits and the other species is harmed.
$B$. Both species benefit in mutualism.
$C$. Both species benefit in commensalism.
$D$. In parasitism, only one species benefits and the other species is harmed.
$E$. In amensalism, one species is harmed and the other is unaffected.