Knowing both the scientific and common names for your species is important. Use both when searching and be sure to check all of the common names.
When doing a search of the library catalog, try using the plural for your search term. For example, "toads" instead of "toad." You may get better results.
A good place to start is encyclopedias. There are encyclopedias for birds, fish, trees and flowers. They are in the Reference collection behind the Reference desk on the 2nd floor. Look for the QK and QL call numbers.
When you find a good reference book, write down the call number, so that you use it to find other information in the 3rd floor shelves. Remember you may not find an entire book about your plant or animal. So you need to check for broader resources. For example, if you are researching whooping cranes, a book about birds may be your best choice.