AS Biology - Organisms that cause disease

Organisms that cause disease

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

• Free from disease
• Able to carry out all the normal physical and metal tasks expected in modern society
• Well fed; balanced diet
• Usually happy with a positive outlook
• Suitably housed with proper sanitation
• Well integrated into society

Disease can be defined simply as a departure from good health caused by a malfunction in the mind or body. This causes symptoms which may be physical, mental, or social. There is a wide range of diseases which 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 an effect on your mental and social health

Parasites

These are organisms that live in or on another living thing (the host). Parasites harm their host. They usually cause harm by taking their nutrition from the host. They may live all or just part of their life on the host. Parasites that live on hosts are called external parasites. Parasites that live inside their host are called internal parasites (like tapeworm). They may live almost unnoticed…