BioOne Digital Library is a great place to search for sources on a topic in biology is the database. The database is contains over 200 journals that cover biological, ecological, and environmental sciences. Note that BioOne Digital Library is used by professionals and contains advanced scientific research.
The videos linked below explain how to use the BioOne Complete database. For written instructions on searching the database, see their Searching BioOne Complete page. For written instructions on using the tools and features of the database, see their Tools and Features page. Note that the Browse Subjects page lets you browse journals by subject, not articles.