NCHHSTP Social Determinants of Health. Definitions. The National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention uses the words below to describe health equity and social determinants of health. These words are also used by the World Health Organization and the Department of Health and Human Service's Healthy People 2020.
Scientists have narrowed down several of the most likely causes of mass extinction. Flood basalt events (volcano eruptions), asteroid collisions, and sea level falls are the most likely causes of mass extinctions, though several other known events may also contribute. These include global warming, global cooling, methane eruptions and anoxic eventsâwhen the earth's oceans lose their oxygen.
See Image 1. Humans can also cause extinction by over-hunting. If sufficient numbers of an animal are killed, their populations can drop to a level from which they cannot recover. An example of this kind of extinction is the Steller's Sea Cow, a marine mammal that was hunted into extinction a few centuries ago.