Biology- Organisms that cause diesease

Health and disease:

Health can be defined as your physical, mental and social well being. If you are in good health, you are:

·         free from disease

·         able to carry out all the normal physical and mental tasks expected in modern society

·         well fed, with a balanced diet

·         usually happy, with positive outlook

·         suitably housed with proper sanitation

·         well integrated into society

Disease can be defined simply as a departure from good health. But this is oversimplified. A disease is a malfunction of the body or mind, which causes symptoms. These symptoms may be physical, mental or social. There is a wide range of diseases that can be grouped into certain categories according to their cause. The diseases caused by living organisms are called infectious diseases. The symptoms are usually physical, but these diseases may have some effects on your mental and social health.

Parasites and pathogens:

Parasites:

Parasites are organisms that live in or on another living thing (the host). Parasites harm their hosts. They usually cause harm by taking their nutrition from the host. They may live all or part of their life in or in the host. Parasites that live on their host are called external parasites. An example is the head louse, which lives in people's hair. Parasites that live in their host are called internal parasites. Tapeworms that live in the digestive system are internal parasites.

Parasites may live almost unnoticed by their host. It is probably better for a parasite to be unnoticed so that the host does not try to remove it. If parasites become too numerous, they may become a huge burden to the host. Parasites may cause damage that…