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    Biodiversity: Endpoints on the Tree of Life

    The Convention on Biological Diversity defines biodiversity as
      "the variability among living organisms from all sources including, inter alia (i.e., "among other things"), 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."

    Biodiversity is the variety of all living species on earth.

    More than 1.7 million species of eukaryotes
    have been described and named.

    This is a mere fraction of all the species out there.

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    So Much Life

    More than half of animal species are insects,
    with more than 350,000 described species of beetles alone.

    There are almost as many described plant species
    as there are non-insect animals.

    But the 1-2 million species known to science do not
    approach the actual number of species on earth.

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    Vast Numbers of Species and Individuals

    Edward O. Wilson has estimated that there may be 5 - 50 million species of eukaryotes.

    That doesn't include the incomprehensible number and diversity of prokaryotes.

    We share the planet with approximately 5 x 1030 (five million trillion trillion)
    bacteria and archaeans.

    A stack of that many pennies would be a trillion light years long.

<-- The diversity of bacteria on different parts of the skin of two human subjects.
xxx Lowest species diversity is shown in blue.
xxxxHighest diversity is shown in red.
xxxx(Bouslimani et al., 2015)

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    Vast Genetic Diversity

    Stretch the DNA of 20,000 genes (typical mammal) and lay them end to end
    The strand would be about 0.2m (~8") long at 20 Angstroms in diameter (actual size).
    • Magnify diameter to 0.5mm; the length would be ~200km (~124 miles).

    • At this magnification there would be about 50 nucleotides/cm

    • The full information encoded, printed as 10 pt. font, would fill FIVE editions of Encyclopedia Brittanica!

    • Here's just the Eleventh Edition, to give you an idea of how many books that is.

    ("Book?" What is this "book" of which you speak?)

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    Mind. Blown.

    There are 50-500 million species on earth,
    each with its own genetic history,
    each comprising thousands to millions to billions
    of individuals.

    Multiply those encyclopedias by THAT.

    The genetic diversity that took 4 billion years to build.

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    The Value of Biodiversity

    Of what use is all this organismal variety?
    • genetic diversity
    • natural biological control of pest species
    • source of food and natural products
    • ecological processes that protect and sustain us
    • enjoyment of aesthetic beauty
    • scientific interest
    • complex ecosystems (diverse) protect their component species
    • unknown future benefits

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    Biodiversity Confers Ecosystem Stability

    Species diversity of ecosystems confers stability to those ecosystems.

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    Zea mays on the Brink of Extinction

    Corn and corn product exports generated $74.7 billion in annual economic output in the U.S. in 2014 (Informa Economics).

    In the mid 1970s highly inbred U.S. domestic corn (Zea mays)
    was attacked by a deadly viral blight that threatened
    to wipe out the nation's entire crop.

  • Domestic corn (Zea mays, 2n=20) was highly susceptible to the virus.
  • A close relative (Zea perennis, 2n = 40) was resistant, but could not hybridize.

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(click on pic for source)

Left: wild maize (Zea mays)
Right: wild relative of maize (Zea diploperennis)
Center: F1 hybrid

    Teosinte to the Rescue

    Biologists working in a Western Mexico forest (being logged out for cow pasture) discovered
    a one hectare stand of a new Zea species ("teosinte").

    • Zea mays (2n=20)
    • Zea diploperennis (2n = 20)

    Hybridization could have two potential benefits:

    • 1. Zea diploperennis is perennial.
    • Longer-lived plants could reduce soil erosion.

    • 2. Z. diploperennis was immune or resistant to seven different viral blights.
    • Hybrids might be resistant to the problematic blight.

    Hybridization was successful!
    Viral resistance was among the dominant alleles
    passed to Zea mays by the wild corn.

    Similar scenarios have played out several times in other domestic crops.

    Losing wild species means losing the genetic "safety net" they provide.

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(click on pic for source)

    Views of Biodiversity: Anthropocentrism

    There are several different ways of valuing wild species.

    The anthropocentric view:

      Non-human species are important only in so far as they can benefit humans
      They are important only as resources.

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(click on pic for source)

    Views of Biodiversity: Biocentrism

    The biocentric view:
      Non-human species have intrinsic value, and should be preserved.

      The biocentric view is often subjective.

      People with this perspective often focusing preservation efforts on large, charismatic species to the exclusion of less aesthetically appealing species
      which could be more ecologically important.

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    Views of Biodiversity: Ecocentrism

    The ecocentric view:
      Ecosystems and the biodiversity comprising them should be preserved.
      The working whole is more important than any single component.

      Disassembling an ecosystem can be likened to disassembling a human body.
      The ecosystem is greater than the sum of its parts.

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Ecological/Conservation Categories

Species can be categorized on the basis of their natural history or ecology.


(click on pic for source)

    Indicator Species

    An indicator species, or bioindicator, is a species that, by its presence, abundance, lack of abundance, or chemical composition, demonstrates some distinctive aspect of the character or quality of an environment.

    • Northern Spotted Owl
      This animal was at the center of a major bioethics controversy in the mid 1980s, pitting environmentalists and scientists against the logging community.

    • Lichens
      Formed by the symbiosis of a fungus and an autotroph, lichens absorb nutrients directly from the air. They cannot tolerate air pollution, particularly sulfates and nitrates, which react with water in their tissues to become strong acids. Presence of lichen is an indication of good air quality.

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(click on pic for source)

    Keystone Species

    A keystone species is a species upon which many other species in an ecosystem rely for survival.

    • marine plankton species
    • Coyote in fragmented Southern California chaparral

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(click on pic for source)

    Native/Indigenous Species

    A native/indigenous species is a species whose presence in a particular region is the result only of natural processes, with no human intervention.

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(Raimund Linke, Getty Images)

    Endemic Species

  • endemic species
      a species native to a particular area and found nowhere else on earth.

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(click on pic for source)

    Exotic Species

    An exotic species is a species that has been introduced anthropogenically to an area where it did not evolve.

    Many ornamental plants fall into this category.
    As long as they do not escape cultivation and invade native ecosystems,
    they are not problematic.

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(click on pic for source)

    Invasive Exotic Species

    An invasive exotic species is an exotic species that aggressively displaces native species.

    Southern Florida is a hotbed of invasive exotics.

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    Conservation Status

    The International Union for Conservation of Nature (IUCN) has devised eight levels that describe species on the basis of population status.
    • Least Concern (LC)
    • Conservation Dependent (CD)
    • Near Threatened (NT)

    • Vulnerable (VU)
    • Endangered (EN)
    • Critically endangered (CR)

    • Extinct in the Wild (EW)
    • Extinct (EX)

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