This is a literary device in which part of something represents a whole or it may be used as a whole to represent its part. Synecdoche means is may also use larger groups to refer to smaller groups.
I mean like is this a serious question?
Relative clauses are types of dependent clauses complete independent sentences - they usually refer to a single word and modify them. Here, in this excerpt, the relative clause would be that we can see in nature. Relative clauses usually begin with pronouns such as who, what, that, etc.
