 Conservation biology clearly concerns conserving something biological or ecological, but what is or should be conserved? Work has focused on a variety of units. As examples, some have focused on species such as the spotted owl Strix occidentalis (Yaffee 1994) and loggerhead turtle Caretta caretta (Bolten &amp; Witherington 2003); some have focused on populations and sub-species such as wild salmon Oncorhynchus spp. (Quinn 2005); some have focused on biomes or eco-regions such as tropical coral in the Great Barrier Reef (Hutchings, Kingsford, &amp; Hoegh-Guldberg 2008); and finally some have focused on genotypes or genetic features such as heterozygosity (Avise &amp; Hamrick 1996). However, in the 1980s, conservation biologists united and argued that biodiversity should be the focus of the discipline (E. O. Wilson 1988; see entry on  biodiversity).  What then is biodiversity? Here is a standard definition from an influential textbook.