Genetic Diversity and Levels of Biodiversity
Biological diversity or biodiversity refers to the variety of life forms: the different plants, animals and microorganisms, the genes they contain, and the ecosystems they form. This living wealth is the product of hundreds of millions of years of evolutionary history.
In places as ancient as Australia, this history can still be seen today in ‘living fossils’ whose origins date back hundreds of millions of years.
Biodiversity is the variety and differences among living organisms from all sources, including terrestrial, marine, and other aquatic ecosystems and the ecological complexes of which they are a part. It is virtually synonymous with “Life on earth”.
Biologists most often define “biological diversity” or “biodiversity” as the “totality of genes, species, and ecosystems of a region. The biodiversity found on earth today consists of many millions of distinct biological species, which is the product of nearly 3.5 billion years of evolution.
Biological diversity or biodiversity is the term given to the variety of life on earth and the natural patterns it forms, the variety and variability of life-forms, both contemporary and extinct, including genetic and ecosystem diversity, in a defined area at and over time.
Biological diversity is a measure of the diversity of all life at all levels of organization. Biodiversity is all of the hereditary variation in organisms, from differences in ecosystems to the species composing each ecosystem, thence to the genetic variation in each of the species.
As a term, biodiversity may be used to refer to the variety of life of all of Earth or to any part of its Living structures called stromatolites which can be seen in Shark Bay, Western Australia, represent one of the longest continual biological lineages known, some 1900 million years.
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The process of evolution means that the pool of living diversity is dynamic: it increases when new genetic variation is produced, a new species is created or a novel ecosystem formed; it decreases when the genetic variation within a species decreases, a species becomes extinct or an ecosystem complex is lost.
The concept emphasizes the interrelated nature of the living world and its processes.
Genetic Diversity
Genetic diversity refers to the variation of genes within species. This covers genetic variation between distinct populations of the same species, such as the four varieties of white-cheeked rosella, Platycercuseximius.
It also covers genetic variation within a population, which tends to be relatively high in widespread eucalypts such as Eucalyptus cloeziana, E. delegatensis, and E. saligna. Genetic diversity can be measured using a variety of DNA-based and other techniques.
New genetic variation is produced in populations of organisms that can reproduce sexually by recombination and in individuals by gene and chromosome mutations.
The pool of genetic variation present in an interbreeding population is shaped by selection. Selection leads to certain genetic attributes being preferred and results in changes to the frequency of genes within this pool.
The large differences in the amount and distribution of genetic variation can be attributed in part to the enormous variety and complexity of habitats, and the different ways organisms obtain their living.
One estimate is that there are 10,000,000,000 different genes distributed across the world’s biota, though they do not all make an identical contribution to overall genetic diversity.
In particular, those genes which control fundamental biochemical processes are strongly conserved across different species groups (or taxa) and generally show little variation. Other more specialized genes display a greater degree of variation.
Figure 1: Genetic variation within the White-cheeked Rosella. Source: Wikipedia
The White cheeked Rosella, for example, is made up of four varieties, each with its own distinct colour combination and markings. The diagram shows where these varieties are found. Genetic variation within a species can express itself in many ways.
Levels of Biodiversity
Biological diversity is usually considered at three different levels:
Genetic diversity refers to the variety of genetic information contained in all the individual plants, animals and microorganisms.
Genetic diversity occurs within and between populations of species as well as between species. Species diversity refers to the variety of living species.
Ecosystem diversity relates to the variety of habitats, biotic communities, and ecological processes, as well as the tremendous diversity present within ecosystems in terms of habitat differences and the variety of ecological processes.
In summary, biological diversity or biodiversity refers to the variety of life forms in ecosystems. These living wealth arise from evolution. Biodiversity portrays the variety and differences among living organisms addressing the hereditary variation in organisms, from differences in ecosystems at genetic, species or ecosystem levels.
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Genetic diversity refers to the variation of genes within and between species and covers genetic variation within a population. It can be measured with a variety of DNA- based and other techniques.
New genetic variation is produced in populations that can reproduce sexually by recombination and in individuals by gene and chromosome mutations. Selection produces some preferred genetic attributes and results in changes in the frequency of genes within the pool.
