Tuesday, May 22, 2012

The Tree of Life

Today features guest blogger Patrice Sherman.

Credit: Library of Congress
Ever hear of the halliaeetus leucocephalus? Of course, you have.  Halliaeetus leucophalus is the scientific name for the bald eagle.  In Latin it means “white headed sea eagle”

John James Audubon drew the bald eagle you see here sometime in the 1820s.  Audubon spent most of his adult life drawing birds.  Between 1819 and 1846 he identified and drew over 435 different species of North American birds.

Why is identifying species important?  The scientific name for a species tells us how it relates to other life forms. Basically, the name is like an “address” on the tree of life.  The major category, or trunk, of the tree is “life “ itself. After that, living organisms are divided into domains and then into ever-smaller categories. The formal hierarchy looks like this:  domain > kingdom > phylum > class > order > genus > species.  So the complete name for our bald eagle is actually: Animalia > Chordata > Ciconiiformes > Accipitridae > Halliaeetus > Halliaeetus leucocephalus. 

Just as species are related to one another, so too are scientists—not biologically, but through their ideas.  This system of classifying species was first developed around 1735 by the Swedish naturalist Carl Linnaeus.  Audubon relied on his copy of Linnaeus’s book when identifying birds in America. In 1826, Audubon traveled to Britain and gave a lecture at the University of Edinburgh, Scotland. Sitting in the audience was a 19-year old student named Charles Darwin.

Five years later, when Darwin visited the Galapagos Islands off the coast of South America, he became fascinated by a species of small bird he called finches. On each island, he noted, the finch population had a different type of beak. His observations led to the discovery 15 new species of birds, and to a theory that would change science forever.          

The process of identifying new species continues to this day.  According to the International Institute of Species Exploration only 20% of all species have been identified. That leaves approximately 8.7 million out there waiting to be discovered.  Each year researchers identify between 18,000-26,000 new species.  Many exist in only remote areas.  Some are so tiny they can only be seen with a microscope. A surprising number, however, are hiding in plain sight.
Photo credit: Colin Osborne, USFWS
 In 2009, Jeremy Fineberg, a student at Rutgers University, discovered a new species leopard of frog on Staten Island. Fineberg knew that most local frogs made a series repetitive croaks, or “chuckles.”  When he listened carefully, this frog only made one chuckle at a time. Three years later, DNA tests certified Fineberg’s frog as a genuine new species. 

 You don’t have to be an expert to discover a new species.  Many are found by ordinary people willing to take a second look, or second listen, to the world around them.  The identification of species encourages us to get right up close to nature, to note the smallest details. 
It also helps us do just the opposite.  When we find new species, we are inspired to step back and take a look at the whole tree of life.   We humans have our place on it, too. That’s us, homo sapiens, perched on our own special branch.  In Latin homo means “man” and sapiens, “knowing.” Every time we name a new species, we add a new twig to the tree. And with every new twig we learn a little more about the diversity of our planet, making the tree of life, a tree of knowledge, indeed.

Patrice Sherman is the author of several books for young readers, including the book Conservation Heroes: John James Audubon.  She likes to enjoy nature at Fresh Pond near her home in Cambridge, Massachusetts.  You can find out more at her website

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