The interjection in this sentence is Yikes!
Interjections are used to express some emotion, and they often end with an exclamation mark.
I can help you with a rough draft; but unfortunately i don’t have access to either of the stories so i cant cite evidence. i’m assuming you can fill in some quotes to help support?
Call of the Wild is a story (based on what i word all have read) that has a lot to do with nature (?) and survival. This ties in with Darwin’s theory of natural selection since it also has to do with evolution of nature and survival and adaptation. (assuming that Call of the Wild also requires adaptation, considering most survival stories do), Call of the Wild relates a lot in how people evolve when being put in risky situations & an outdoor environment.
Two things to keep in mind when you're deciding whether to use formal or informal English are the B) occasion and the audience.
Of course you are going to change the way you talk depending on whether you are speaking to your friends or to your teacher - usually with the teacher you are going to use more formal English.
Occasion is also important - you won't speak in the same manner at a party and a cocktail.
