The term “biodiversity” was not coined until the 1980s, when it was popularised by the eminent Harvard biologist E. O. Wilson. The most tangible manifestations of biodiversity are the species of plants, animals and micro-organisms that surround us. Yet biodiversity means more than just species diversity. At the micro level, it includes the genetic material that makes up the species, whereas at the macro level, it covers natural communities, ecosystems and landscapes. Biodiversity essentially relates to the full array of life on Earth.
In an apparently continuous movement, biodiversity emerged over the course of the geological eras, wending its way through both biological evolution and periods of mass extinction. Such diversification of the living world is made possible by the genetic adaptation of species to environmental changes, whether natural or human caused. Communities themselves evolve on the basis of fluctuations in their environment, according to complex historical processes that explain the present state of the biosphere. The first living beings appeared in the oceans roughly 3.5 billion years ago in the form of primitive bacteria, which subsequently diversified into the multitude of organisms of every shape and size and are now classified under five kingdoms (animal, plant, fungi, bacteria, and protists), each of which is divided into systematic classifications that emerged following the branching out of the particular species. Humankind has still a long way to go before acquiring a complete knowledge of the species that populate the Earth.