BIODIVERSITY - the variety of living species on earth.

1.5 million described species on earth.

What is a species?

Species: a population or series of populations within which free gene flow occurs under natural conditions.

(i.e. - a group of similar organisms which can interbreed to produce fertile, viable offspring under natural conditions)

"Conspecifics" are members of the same species. For example, all of us in this classroom are conspecifics of one other. Unless you're hiding something pretty well.)

E.O. Wilson (eminent ant biologist from Harvard) estimates that there may be anywhere from 5 - 50 million species on earth.

What makes all those species different from one another? It's the information for BUILDING those organisms, which are encoded in the GENES.

Cast your eyes skywards, to the periodic table of elements...
All living things are composed of MOLECULES.
A molecule is two or more ATOMS (composed of protons (+) and neutrons (0) to make the nucleus, and orbited by electrons (-) bonded together. They may be the same type of atom (which means that the molecule is an ELEMENT), or they may be different types of atoms (which means that the molecule is a COMPOUND).

Examples of elements: O2, H2, N2, etc.
Examples of compounds: H2O, CO2, CH3, etc.

An ORGANIC molecule is one which has a basic "skeleton" made of CARBON (C) and HYDROGEN. They are so named because these types of molecules usually are made only by LIVING ORGANISMS. (That's changed with the advent of modern chemistry--but originally, organic molecules were made almost exclusively by living organisms.)

Examples of organic molecules: CH3 (methane), benzene (C6H6), the sugar glucose (C6H12O6), etc.

An INORGANIC molecule is one that lacks that CARBON-HYDROGEN backbone. Examples are all the elements and compounds I listed above (except for the methane, CH3).

The structural components of the bodies of all living things are mostly very large, compound molecules known as BIOLOGICAL MACROMOLECULES (though there are lots of other inorganic and smaller organic molecules throughout the body, too). The four main types of biological macromolecules are...

  • CARBOHYDRATES
  • LIPIDS (fats)
  • PROTEINS
  • NUCLEIC ACIDS (DNA and RNA)

    Genes are composed of the latter type, and are permanently stored in the nucleus of each and every cell in any living organism's body as DNA (DeoxyriboNucleic Acid).

    The genes form a blueprint for the organism's cells which tell it how to make the specific PROTEINS that give it it's unique identity. Proteins can be

  • structural (e.g., silk, keratin)
  • functional (e.g., enzymes)
  • or even both! (e.g., myosin, actin--muscle proteins)

    In essence, the genes of all living things form a vast "library" of instructions for making proteins, of which there are literally billions, some similar to each other and some completely unique.

    Average mammal: 100,000 genes

    (but the range in genes goes from about 1000 (in bacteria) to more than 400,000 in some ferns and flowering plants)

    *The DNA of a single mammal cell, laid end to end and stretched out, would be about 1m long. (20 Angstroms in diameter)

    *If you were to magnify this strand to the diameter of a common wrapping string (about 0.5mm), this would measure 960 km!

    *At this magnification, there are about 50 nucleotides per cm.

    *The full information therein, if translated into 10 pt. text, would fill all 15 editions of the Encyclopedia Brittanica published since 1768! (About 20-30 volumes per edition!).

    Multiply this by all the members of a species, and then by potentially 50 million species, and you get an idea of the immeasurably vast genetic library that the earth has generated over the 3.5 billion years that life has inhabited it.

    The Saga of Zea mays: domestic corn

    Inbreeding (mating between closely related individuals) results in greater homozygosity at deleterious gene loci, and the expression of genetic disorders.

    Zea mays crops in the U.S. were attacked by an extremely virulent blight that threatened to wipe out the crops completely. (Early 1970's)

    Biological team in Honduras discovered about a one hectare stand of wild cousin of Zea mays, Zea diploperennis, in an area of the Yucatan peninsula that was being logged out for cattle pasture.

    This was hybridized with the domestic varieties, and conferred blight resistance to the crops. The industry was saved.

    Wilderness as a resource

    anthropocentric view: non-human species are important only in so far as they can benefit humans

    biocentric view: non-human species are important to save for their own, intrinsic value.

    (often subjective; often focuses on "charismatic" species such as whales, Spotted Owls, baby seals etc.)

    ecocentric view: biodiversity and ecosystems should be preserved--not just individual species or populations.

    Species in peril:

    threatened: still relatively abundant in isolated areas of its former range, but likely to become more scarce, usually due to habitat loss.

    endangered species: so few individuals left that extinction is imminent. (e.g. - California condor, snow leopard, Siberian tiger, snail darter, cheetah, white rhino etc.)