KNOW MORE ABOUT BIODIVERSITY 

BY;MY ENVIRONMENT

The word "biodiversity" is a contracted version of "biological diversity". The Convention on Biological Diversitydefines biodiversity as:"the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species, and of ecosystems." 

Thus, biodiversity includes genetic variation within species, the variety of species in an area, and the variety of habitat types within a landscape. Perhaps inevitably, such an all-encompassing definition, together with the strong emotive power of the concept, has led to somewhat cavalier use of the term biodiversity, in extreme cases to refer to life or biology itself. But biodiversity properly refers to the variety of living organisms.

General interest in biodiversity has grown rapidly in recent decades, in parallel with the growing concern about nature conservation generally, largely as a consequence of accelerating rates of natural habitat loss,habitat fragmentation and degradation, and resulting extinctions of species. The IUCN Red List estimates that 12-52% of species within well-studied higher taxa such as vertebrates and vascular plants are threatened with extinction. Based on data on recorded extinctions of known species over the past century, scientists estimate that current rates of species extinction are about 100 times higher than long-term average rates based on fossil data. Other plausuble estimates suggest that present extinction rates now may have reached 1000 to 10,000 times the average over past geologic time. These estimates are the basis of the consensus that the Earth is in the midst of the sixth mass extinction event in its history; the present extinction event is termed the Holocene Mass Extinction.

The Magnitude of Biodiversity

Species can be grouped on the basis of shared characteristics into hierarchical groups, or taxa, reflecting their shared evolutionary history. At the highest level of classification (or deepest branches in the evolutionary tree of life) organisms are divided into three Domains: 1) the Bacteria, which are microorganisms lacking a cellular nucleus or other membrane-bound organelles; 2) the relatively recently discovered Archaea, microorganisms of primarily extreme environments such as hot springs, which are superficially similar to Bacteria but fundamentally different at biochemical and genetic levels; and 3) the Eukarya, which include all other organisms based on nucleated cells. The Eukarya includes the four "kingdoms", the protists, animals, plants, and fungi. Each of the eukaryotic kingdoms in turn is divided into a number of phyla. At this higher taxonomic level, the oceans are far more diverse than those on land, likely reflecting the marine origins of life on Earth. Nearly half the phyla of animals occur only in the sea (e.g., the sea stars and other echinoderms), whereas only one (the obscure Onychophora, or velvet worms) is restricted to land.

Ecological controls on biodiversity

A central question in explaining these patterns of diversity is determining the relative importance of long-term evolutionary processes -- the balance between origin and extinction of species -- and local ecological processes of species interactions.

The general similarity among diversity patterns of different taxa with latitude and region suggests that prehistorically these patterns have been controlled primarily by factors operating over large spatial and temporal scales. Ultimately, the number of species in a region is set by a balance between origin through speciation, loss through extinction, and migration of species among regions, all of which operate over long (geologic) time scales.

Conversely, on local spatial scales and over ecological time scales on the order of a few generations of organisms, a wealth of evidence shows that diversity often varies systematically with habitat area, habitat heterogeneity, disturbance, and availability of energy (i.e., productivity) and other resources, notably water in terrestrial ecosystems.

Human disturbance factors

For the most recent 10,000 years man has been the greatest factor affecting biodiversity, with adverse impacts occurring at an accelerating pace since approximately the Industrial Revolution. Human intervention in ecosystem function have been expressed through habitat destruction, habitat fragmentation, overexploitation, and pollution. In some locations such as Easter Island and Hawaii the majority of macroscopic species that existed as recently as the mid-Holocene are now extirpated. READ MORE ON http://www.eoearth.org/view/article/150560