A disease is any condition which results in the disorder of a structure or function in a living organism that is not due to any external injury. The study of disease is called pathology, which includes the study of cause. Disease is often construed as a medical condition associated with specific symptoms and signs. It may be caused by external factors such as pathogens or by internal dysfunctions, particularly of the immune system, such as an immunodeficiency, or by a hypersensitivity, including allergies and autoimmunity.
Tropical coral reefs are home to an enormous variety of marine life; however, they are under threat from human activities and rising sea levels due to climate change. A better understanding of the ecological mechanisms that take place within tropical coral reefs will help to ensure their conservation.