What is a Species?

To this day, scientists struggle with that question. A better definition can influence which animals make the endangered list

By Carl Zimmer | Monday, May 19, 2008

If you visit Algonquin Provincial Park in Ontario, you may hear the high, lonesome howls of wolves. You may even be lucky enough to catch a glimpse of a distant pack racing through the forests. But when you show off your blurry pictures back home, what species should you boast that you saw? Depending on the scientist you ask, you may get a different answer. Some may even offer you a few different answers all at once.

In the 18th century European naturalists dubbed the wolves of Canada and the eastern U.S. Canis lycaon, because they seemed distinct from Canis lupus, the gray wolf of Europe and Asia. By the early 1900s North American naturalists had decided that they were actually gray wolves as well. But in the past few years Canadian researchers who have analyzed wolf DNA have come full circle. They argue that gray wolves only live in western North America. The wolves of Algonquin Provincial Park belong to a separate species, which they want to call C. lycaon once more.

Formal taxonomic systems first identified species based on visual traits such as fins or fur. Later, the species concept changed, specifying that two organisms should be capable of breeding.
Today biological diversity can be ascertained by sampling DNA and tracking how a species descended from a common ancestor.

The debate over species definition is far from over and is more than a mere academic spat. Proper classification is essential for designating the endangered list.

Dichotomous Key

A dichotomous key is a powerful tool for use in biology or any of the life sciences. It is also used in logic problems, physical sciences, and many other avenues. They are identified by having a choice of one of two options. Each selection will lead you to another pair of choices that ultimately leads to a final conclusion or organism identification.

They can be used in various fashions, from sorting playing cards
playing card key

to identifying trees (while this is not a true dichotomous key – there are more than two choices for some of the steps – it helps show the branching process).

For more practice, try the following site:


If you have a tree that you are trying to identify, dichotomous keys are a good way to figure out what species you are dealing with. If you have a tree that you are trying to identify, try using the following dichotomous key from the OSU website: