Describe the three ways that biodiversity is defined

!.) Biodiversity is the variation of a species throughout an ecosystem 
2.) Biodiversity forms the foundation of the vast array of ecosystem services that critically contribute to human well-being. and3.)  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.

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Genetic diversity is the variety present at the level of genes. Genes, made of DNA, are the building blocks that determine how an organism will develop and what its traits and abilities will be. This level of diversity can differ by alleles (different variants of the same gene, such as blue or brown eyes), by entire genes (which determine traits, such as the ability to metabolize a particular substance), or by units larger than genes such as chromosomal structure.

Species DiversityBiodiversity studies typically focus on species. They do so not because species diversity is more important than the other two types, but because species diversity is easier to work with. Species are relatively easy to identify by eye in the field, whereas genetic diversity (above) requires laboratories, time and resources to identify and ecosystem diversity (see below) needs many complex measurements to be taken over a long period of time. Species are also easier to conceptualize and have been the basis of much of the evolutionary and ecological research that biodiversity draws on.Species are well known and are distinct units of diversity. Each species can be considered to have a particular "role" in the ecosystem, so the addition or loss of single species may have consequences for the system as a whole. Conservation efforts often begin with the recognition that a species is endangered in some way, and a change in the number of species in an ecosystem is a readily obtainable and easily comprehensible measure of how healthy the ecosystem is.

Ecosystem-level theory deals with species distributions and community patterns, the role and function of key species, and combines species functions and interactions. The term "ecosystem" here represents all levels greater than species: associations, communities, ecosystems, and the like. Different names are used for this level and it is sometimes divided into several different levels, such as community and ecosystem levels; all these levels are included in this overview. This is the least-understood level of the three described here due to the complexity of the interactions. Trying to understand all the species in an ecosystem and how they affect each other and their surroundings while at the same time being affected themselves, is extremely complex