 What
is biodiversity?
Definition
Biodiversity in the bacteria in your stomach, the algae in a pond,
the spiders in your house, the genes that are the code to create
a human, a small patch of grassland, the mosaic of habitats on an
island, the Amazon rain forest. In short biodiversity is the variety
of life on earth, at all levels, from genes, through to individual
organisms to species to vast and expansive habitats and the links
and interactions between all of these.
The most widely accepted definition for biodiversity is contained
within the Convention on Biological
Diversity:
‘Biological diversity’ means the variability among
living organisms from all sources including, among other things,
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.
Levels
Biodiversity can be expressed in different ways. One useful way
to look at the variation is to break it down into different levels
of biological organisation:
• Genetic diversity
• Species diversity
• Ecological diversity
(For a full biodiversity glossary of terms click
here)
Breaking diversity down into different levels is a useful way of
looking at the variation but the levels are intimately linked and
interact and affect one another. For example genetic diversity can
be having a population of moths where some individuals have a gene
that makes them camouflaged against a tree with lichen on the bark
and some having a gene that makes them camouflaged against a tree
with pollution damaged black bark. If pollution increases and more
trees get black bark the moths that are camouflaged against this
will increase in the population since they are less likely to be
seen and hence eaten by birds. The environment affects the genes
which affect the diversity within the species and this could affect
the ecological diversity as different predators may be affected
in different ways by different densities of the two colours of moth.
Drawing lines between where one type of diversity starts and where
another type begins is not always possible as there is usually a
large amount of overlap. Biodiversity is a continuum and the levels
help us simplify a complex system. While many of the elements of
biodiversity may be difficult to define rigorously, and in some
cases may have no strict biological reality, they remain useful
and important tools for thinking about and studying biodiversity.
Along with the evolutionary process, the hierarchical organization
of biodiversity reflects one of the central organising principles
of modern biology.
Whether any one element of biodiversity, can be regarded in some
way as the most fundamental, essential or even natural is a contentious
issue. For some, genes are the basic unit of life. However, in practice,
it is often the species that is treated as the most fundamental
element of biodiversity. There are however many definitions of species
which can be used. Click here
to see different species definitions.
Photo Credit: Nigel Harper, Flamingos
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