The field of biodiversity was born when scientists began to realize that 99 percent of all species that have ever existed are now extinct, and that four more are becoming extinct each hour of the day and night. Answers to the basic questions of how life began, how it is formed, how life is threatened, and where we are headed. This fascinating survey offers an introduction to the subject for the general reader, complete with photos and charts to make the bewildering more comprehensible. It covers viewpoints that range from doomsday theories to don't-worry-be-happy attitudes, while offering constructive ways average citizens can respond to the fact that the life we save may be that of our planet. 160 pages (50 in color), 7 1/2 X 9 1/2.