What does the following figure represent?

Which of the following relationships cannot be described as a negative interaction?

What is the effect of a parasite on the host?

Observe the set of $4$ figures $A$,$B$,$C$ and $D$ and answer the following questions:
$(i)$ Which one of the figures shows mutualism?
$(ii)$ What kind of association is shown in $D$?
$(iii)$ Name the organisms and the association in $C$.
$(iv)$ What role is the insect performing in $B$?

In an aquarium,two herbivorous species of fish are living together and feeding on phytoplanktons. As per the Gause's Principle,one of the species is to be eliminated in due course of time,but both are surviving well in the aquarium. Give possible reasons.

Which of the following is an example of a positive interaction in a population?