Lichens represent a symbiotic relationships between algae and
a) fungi.
b) diatoms.
c) protists.
d) microscopic anima

A. fungi

Symbiotic relationship would be a mutuality of organisms where the other shares a deep physiological and psychological share of individuality. 
There are several types of biotic relationships that is occurring every single moment in the ecosystem and one is parasitism. In this scenario with human beings and mosquitos, this phenomenon of interaction is distinguished as parasitism where mosquitos draws blood that contains nutrients from the human tissue to use it as its source of food and then leaves harmful substances and bacteria in the human’s blood stream. 

I’m not exactly sure what your trying to ask, but if it’s how an organelle is similar to a body system or a part a nucleus is like a in function. but i don’t fully understand what you’re trying to ask