Sometimes, the hardest part about doing library research is coming up with the right terms to use in search engines. You can start with your class reading. Another good place is to check the library's catalog for encyclopedias, dictionaries, and handbooks related to your topic (e.g., "evolution encyclopedia"). You will probably find a narrower topic of interest and the article will help you to decide which keywords to use.
Another way to find keywords to use is to do a search in one of the library's research databases. For example, I did a search for "behavior evolution" in ProQuest and found the article "Animal Behaviour: Evolution and Mechanisms". Going to the web page for the article, I see the subjects listed are Veterinary Science, Psychology, Biology-Zoology, and Anthropology. Often, the article itself will include keywords. You can use the subjects and keywords to build your search.
If you are looking for information on a specific animal or plant, you need to be careful. Say you are looking for how parasites change behavior in animals. That topic is too broad. What kind of parasites and what types of animals? Are you interested in cats in general (felids, felines, or family Felidae)? Or are you interested in the domestic cat (Felis catus)? Always use the scientific name in your search because a mountain lion can be called cougar, panther, puma, painter, and catamount, among others. But, no matter what common name is used, it will always be referred to as Puma concolor (formerly Felis concolor) in the scientific literature.
Using one or two words usually isn't the most effective search strategy. It usually brings up too many results. So, you need to construct a more sophisticated search using Boolean operators.
Show only those results that include all terms (most search engines use the AND operator as the default).
Example: genetics AND evolution - includes all articles that use both the words genetics and evolution (the intersection of genetics and evolution).
Show results that include any of the keywords.
Example: genetics OR evolution - includes all articles that include the either the word genetics or evolution (this also includes all articles for that use both words).
Do not show results that include the "not" keyword.
Example: genetics NOT evolution - includes only articles that use genetics; all articles that use evolution are excluded.
Most search engines and journal databases allow you to "nest" your keywords much like a mathematical equation. This allows you to get much more specific with your search.
Example: (genetics AND behavior) AND (Drosophila OR Musca) NOT formosana - includes articles that use both the words genetics and behavior as well as either the word Drosophila or the word Musca (or both), but any article that includes either D. formosana or M. formosana is excluded.