Ernst Haeckel was a 19th-century German naturalist and liberal non-conformist.

Ernst Haeckel.  Photo Credit: University of California Berkeley.

Haeckel was born in Potsdam, Germany in 1834.  Despite an early interest in nature, he was encouraged by his father to study medicine.  He received a medical license after six years of study in Wurzburg, Vienna, and Berlin.  However, he soon returned to the University of Jena to study zoology, becoming a professor of the subject in 1862.

Haeckel held many of the radical beliefs of the day.  He agreed with Darwin on the subject of evolution and developed theories of his own, stemming from Darwin's.  Some of these are explored in his 1899 book, The Riddle of the Universe, which proposed that the development of a creature reflects and demonstrates its evolutionary progress.  This idea, however, has subsequently been proven inaccurate.  Haeckel wrote other books as well and called attention to the connections between various species of animals.  He was the first to draw up a family tree as a way of mapping these connections.

Haeckel is also known for originating, in 1869, the term "ecology," which he defined as the economy of nature.  He died in 1919.