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The most straightforward definition of biodiversity is "variation of life at all levels of biological organization".

Biodiversity found on Earth today is the result of 4 billion years of evolution. The origin of life is not well known to science, though limited evidence suggests that life may already have been well-established only a few 100 million years after the formation of the Earth. Until approximately 600 million years ago, all life consisted of bacteria and similar single-celled organisms.

Biodiversity is not distributed evenly on Earth. It is consistently richer in the tropics. As one approaches polar regions one finds fewer species. Flora and fauna vary depending on climate, altitude, soils and the presence of other species.

Introduction

The word "biodiversity" is a contracted version of "biological diversity". The Convention on Biological Diversity defines 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.

Biological diversity is of fundamental importance to the functioning of all natural and human-engineered ecosystems, and by extension to the ecosystem services that nature provides free of charge to human society. Living organisms play central roles in the cycles of major elements (carbon, nitrogen, and so on) and water in the Environment, and diversity specifically is important in that these cycles require numerous interacting species.

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.

Protecting Ecosystems is vital for preserving biodiversity

Definitions

The most straightforward definition is "variation of life at all levels of biological organization". A second definition holds that biodiversity is a measure of the relative diversity among organisms present in different ecosystems. "Diversity" in this definition includes diversity within a species and among species, and comparative diversity among ecosystems. A third definition that is often used by ecologists is the "totality of genes, species, and ecosystems of a region". An advantage of this definition is that it seems to describe most circumstances and present a unified view of the traditional three levels at which biodiversity has been identified:

GENETIC DIVERSITY 
SPECIES DIVERSITY 
ECOSYSTEM DIVERSITY

The 1992 United Nations Earth Summit in Rio de Janeiro defined "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 part: this includes diversity within species, between species and of ecosystems"

This is, in fact, the closest thing to a single legally accepted definition of biodiversity, since it is the definition adopted by the United Nations Convention on Biological Diversity. If the gene is the fundamental unit of natural selection, according to E. O. Wilson, the real biodiversity is genetic diversity. For geneticists,biodiversity is the diversity of genes and organisms. They study processes such as mutations, gene exchanges, and genome dynamics that occur at the DNA level and generate evolution.

Benefits of biodiversity

There are a multitude of benefits of biodiversity in the sense of one diverse group aiding another such as:

Food and drink

Biodiversity provides food for humans. About 80 percent of our food supply comes from just 20 kinds of plant. Although many kinds of animal are utilised as food, again most consumption is focused on a few species.

There is vast untapped potential for increasing the range of food products suitable for human consumption.

Medicines

A significant proportion of drugs are derived, directly or indirectly, from biological sources. However, only a small proportion of the total diversity of plants has been thoroughly investigated for potential sources of new drugs.

Industrial materials

A wide range of industrial materials are derived directly from biological resources. These include building materials, fibres, dyes, resins, gums, adhesives, rubber and oil. There is enormous potential for further research into sustainably utilising materials from a wider diversity of organisms.

Ecological services

Biodiversity provides many services that we take for granted. It plays a part in regulating the chemistry of our atmosphere and water supply. It is directly involved in recycling nutrients and providing fertile soils. Experiments with controlled environments have shown that we cannot easily build ecosystems to support ourselves.

Leisure, cultural and aesthetic value

Many people derive value from biodiversity through leisure activities such as enjoying a walk in the countryside, birdwatching or natural history programs on television.

Biodiversity has inspired musicians, painters, sculptors, writers and other artists. Many cultural groups view themselves as an integral part of the natural world and show respect for other living organisms.

Threats to biodiversity

During the last century, erosion of biodiversity has been increasingly observed. Some studies show that about one of eight known plant species is threatened with extinction. Some estimates put the loss at up to 140,000 species per year. This figure indicates unsustainable ecological practices, because only a small number of species come into being each year.