1. A pathogen or infectious agent is a biological agent that causes disease or illness to its host.

2. Bacteria cause illness by releasing chemicals that are toxic to the host or by destroying healthy body cells. Example: tuberculosis

Viruses enter the body and take over healthy a cell, which leads them to stop performing their normal tasks. Example: HIV

Fungi go into the body then break the cell wall and use its nutrients to grow. Example: zygote fungi

Protozoa are singled organisms that feed on other cells. Example: ameba

Parasites are organisms that grow and feed on the host some can even kill the host. Example: filaria

3. Pathogens can be transferred by direct or indirect contact with an infected area. They also can be transmitted by the air, water, animal bites and sexual intercourse.

4. The body system that fights off pathogens and infection is called the immune system. The immune system several defenses the first one is the skin. Second, sense the body has openings such as the nose and mouth the immune system builds mucous to trap the incoming pathogens. The last defenses once a pathogen gets into the body is that B cells and T cells are sent to attack it.

5. Nonspecific responses happen the same way in every pathogen such as inflammation and fever. Specific responses are different for each infection because they are specialized to their certain pathogen such as antigens.

6. A vaccine is a substance that is put