The existence of many species depends on the survival of others. Humans are no exception. In the past 14,000 years, many organisms have left indelible marks and exercised on human history. The roles that individual species play in providing food, unique medical compounds, air, and water purification are vital to our health and survival. Some of the organisms were domesticated by our ancestors, and thus improving the quality of our life. Humans also had profound effects on other organisms by altering natural environments and their species compositions from wild to domesticated. This course was designed to provide a brief background on the relationship between humans and 12 selected organisms, and discuss how organisms living in mutual benefit with humans. Field trips to Taipei Zoo and/or Botanical Garden may also be arranged.