Phenomena which commonly bring about death include predation, malnutrition,
accidents resulting in terminal injury, and disease. Death of an entire species is known as extinction. Human activity has increased the number of extinctions in recent times, one cause, for example, being the destruction of ecosystems as a consequence of the spread of industrial technology.
Almost all animals fortunate enough to survive hazards to their existence eventually die from senescence. Rare and remarkable exceptions include the hydra and the jellyfish turritopsis nutricula, both thought to be, in effect, immortal. Causes of death in humans as a result of intentional activity include suicide, homicide and war. From all causes, roughly 150,000 people die around the world each day.
Physiological death is now seen as less an event than a process: conditions once considered indicative of death are now reversible. Where in the process a dividing line is drawn between life and death depends on factors beyond the presence or absence of vital signs. In general, clinical death is neither necessary nor sufficient for a determination of legal death. A patient with working heart and lungs determined to be brain dead can be pronounced legally dead without clinical death occurring. Precise medical definition of death, in other words, becomes more problematic, paradoxically, as scientific knowledge and medicine advance.