4: Introduction to the Biodiversity Hierarchy
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To effectively conserve biodiversity, we need to be able to define what we want to conserve, determine where it currently occurs, identify strategies to help conserve it, and track over time whether or not these strategies are working. The first of these items, defining what we want to conserve, is complicated by the remarkable diversity of the organisms themselves. This is a product of the genetic diversity of the organisms, that is, variation in the DNA (deoxyribonucleic acid) that makes up the genes of the organisms.
Genetic diversity among organisms exists at the following different levels:
- within a single individual;
- between different individuals of a single population;
- between different populations of a single species (population diversity);
- between different species (species diversity).
It can be difficult, in some cases, to establish the boundaries between these levels of diversity. For example, it may be difficult to interpret whether variation between groups of individuals represents diversity between different species, or represents diversity only between different populations of the same species. Nevertheless, in general terms, these levels of genetic diversity form a convenient hierarchy for describing the overall diversity of organisms on Earth.
Similarly, the functional and spatial aspects of biodiversity can also be discussed at a number of different levels; for example, diversity within or between communities, ecosystems, landscapes, biogeographical regions, and ecoregions.
- Genetic Diversity
- refers to any variation in the nucleotides, genes, chromosomes, or whole genomes of organisms.
- the populations of different species that naturally occur and interact in a particular environment.
- a community plus the physical environment that it occupies at a given time.
- a mosaic of heterogeneous land forms, vegetation types, and land uses (Urban et al., 1987).
- a relatively large unit of land or water containing a geographically distinct assemblage of species, natural communities, and environmental conditions (WWF, 1999). The ecosystems within an ecoregion have certain distinct characters in common (Bailey, 1998a).