Your lecturers expect you to acknowledge all
the sources you use in your work.
For definition and details of citing and referencing see:
When writing your assignments in college you will be expected to build your ideas by referring to the work and research findings of other writers.
Quoting, which is the use of the exact words of another writer in inverted commas (" . . . ." , is very rarely used in the sciences.
Instead you will be expected to:
paraphrase (to express the original author's ideas in your own words)
summarise (to express the most important facts or ideas abut something in a short, clear way).
Remember - you still need to provide a reference when you summarise or paraphrase.
Common knowledge is general knowledge that most people would know such as "Paris is the capital fo France" or "There are 60 minutes in an hour". You don't need to cite common knowledge. But remember it varies from culture to culture and also from discipline to discipline.
So a statement such as "The Big Bang theory states that the universe began billions of years ago as a result of an enormous explosion" is considered common knowledge.
But a statement such as "Alpher argued that the Big Bang would create hydrogen, helium and heavier elements in the correct proportions to explain their abundance in the early universe" is not common knowledge and would need to be cited.
When you are deciding whether something is common knowledge or not ask yourself these questions: