science; chapter 4

• the immune system is the body's defense against infection
• what is a disease?

  An abnormal condition that affects the body or mind, causing dysfunction or discomfort.
• what is meant by an infectious disease?

  a disease that can be transmitted from one individual to another.
• what is meant by a non-infectious disease?

  a disease that cannot be transmitted from one individual to another.
• what are pathogens?

  organisms that cause diseases.
• what are some examples of pathogens?

  Bacteria, viruses, fungi, protozoa, worms.