What is a species?
What is a species? To this day, scientists struggle with that question. A better definition can influence which animals make the endangered list.
Standard taxonomic systems (top) first identified species based on visual traits such as fins or fur. Carl Linnaeus developed the basis for modern taxonomy in the 1600s, sorting all things biological into hierarchical groupings that range from the kingdom level (such as animals, plants, fungi) down to individual species, each having a unique collection of observable traits.
Next, the phylogenetic species concept emerged from a new approach to classifying life, known as phylogenetic systematics (middle)—It classifies an individual species as an organism that shares a common ancestor with other species but is set off from others by having acquired newer, distinctive traits. A phylogenetic tree, also known as a tree of life, shows how different species branch off from a common ancestor as they acquire traits the ancestor did not have.
Biologists have always had difficulty grouping microbes into species (bottom). Bacteria do not engage in sex as we normally think of it. They just divide in two—and genetic differences between bacteria that purportedly belong to the same species based on similar outward appearance and behavior can be huge. Some researchers assert that bacteria can be classified as separate species by genetics and ecological niche. At a hot spring in Yellowstone National Park (photograph), different species of the cyanobacterium Synechococcus inhabit different depths or areas of varying temperature (niches).
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. Read the full article here: What is a Species?
Project: Infographic illustration and layout.
Client: Scientific American