Chapter 9
background extinction During most of the 3.56 billion years that life has existed on the earth, there has been a continuous, low level of extinction of species known as background extinction. endangered species has so few individual survivors that the species could soon become extinct over all or most of its natural range (the area in which it is normally found). extinction rate expressed as a percentage or number of species that go extinct within a certain time period such as a year. HIPPCO Habitat destruction, degradation, and fragmentation; Invasive (nonnative) species; Population and resource use growth (too many people consuming too many resources); Pollution; Climate change; and Overexploitation.