The search terms or keywords you use to search are what determine the results you get. Here's a good exercise to help you generate keywords:

1. Express your topic in a topic sentence:  "What is the effect of water pollution on freshwater amphibian populations?"

2. Generate keyword search terms by identifying the main ideas or concepts within the topic sentence: "What is the effect of water pollution on freshwater amphibian populations?"  --> effect, pollution, freshwater, amphibian

3. Expand your search terms by brainstorming related terms or synonyms that describe your main ideas:

• Effect:  impact
• Pollution: pesticide, acidity, pH, heavy metals
  
• Freshwater: river, stream, lake, pond
  
• Amphibian: frog, salamander

Searching for exact phrases instead of individual words can focus your search so that more results are directly relevant to your topic. Different databases and search engines accomplish this in different ways. Two common ones are:

• Quotation marks - Some databases treat words enclosed within quotation marks as phrases. Searching "Atlantic coastal wetlands" will find only results containing those three words next to each other in that order.
• Default setting - In some databases, words typed next to each other are automatically searched as an exact phrase. Searching Atlantic coastal wetlands will only find results containing that exact phrase

Remember: Exact phrase searches can focus your results, but they can also miss some relevant results. Searching the phrase "Atlantic coastal wetlands" will not find wetlands of the Atlantic coast or coastal wetlands of North Carolina, both of which are relevant.

You can create complex search strategies by combining keywords using the linking words AND, OR, and NOT. For example, if your search terms are biodiversity and wetlands:

• AND - Narrows and focuses the search results. The search biodiversity and wetlands finds only results containing both the terms biodiversity and wetlands.
• OR - Broadens the search results. Searching biodiversity or wetlands will find results containing the term biodiversity or the term wetlands or both terms in the same result.
• NOT - Excludes any result containing the term listed after the not.  The search biodiversity not wetlands will find results containing the term biodiversity but not containing the term wetlands. Use not cautiously since it excludes all mentions of the term in every context.