Just plug into the first link that was posted for the citation machine, I used the crap out of that thing with all my papers in college. 3-4 paragraphs is nothing that can't be done in a matter of 15 minutes honestly, as long as you know your subject matter and have a list of citations ready to go as sources. Wait till the real work comes if you take any 4000 level or 5000 level biology courses. Most require a full semester long research project followed by a research paper, minimum of 10 pages long! Enjoy the easy ones while you can :-)
*note* if you ever get stuck finding new sources, go back to your primary sources, and look at their literature cited section at the end of the papers. Look up their sources and find out if any of them are relevant. In a small paper like this, I don't imagine you need more than 1-3 sources anyway, but for future references you may need 10-20 sources within the last 4 years!