Biodiversity is the web of life that distinguishes planet Earth from the other lifeless spheres in our solar system, if not the universe.
Biodiversity is short for biological diversity. It describes the variety of living organisms of all kinds -- animals, plants, fungi, and microorganisms -- that inhabit a particular area.
Most commonly, biodiversity is measured by the number of species present in an ecosystem, but genetic diversity within those species and the diversity of different ecosystems across the landscape are also important.
The diversity of subdivisions of species, such as subspecies and populations, is important as well, since it is the raw material for the evolution of new species in the future.
Scientists have identified and described about 1.4 million species.
Only a small proportion of these are the organisms we're commonly acquainted with:
of the 1.4 million known species, only about 4,000 are mammals and 9,500 are birds.
Over half of all known species are insects. Far more species in the world remain unknown to science.
Estimates of just how many vary, but there are probably between two and twenty times as many unknown species as known ones.