This colorful image represents a virus that commonly causes respiratory infections in people. Living organisms called bacteria are also common causes of human infections. Are viruses living organisms as well?
Actually, this is one of the great unanswered questions of life science. Some scientists think viruses should be considered living organisms. Other scientists disagree. In this chapter, you’ll learn the basic characteristics of living things and the characteristics of viruses. At the end of the chapter, you can decide for yourself whether you think viruses are living organisms.