The origins of species
Part 2 of two parts
The "Tree of Life" by Charles Darwin,
and by others up to the present time.
1 Charles Darwin drew this "tree of life" in his personal notebook with the caption:
"I think case must be that one generation should have as many living as now. To do this and to have as many species in same genus (as is) requires extinction. Thus between A + B the immense gap of relation. C + B the finest gradation. B+D rather greater distinction. Thus genera would be formed. Bearing relation to ancient types with several extinct forms."
1844: 2 An anonymous author published a book in England titled: "Vestiges of the Natural History of Creation." It contained an elementary tree diagram showing how fish (F) first branched from the main evolutionary path at point "A", followed in turn by reptiles (R) and birds (B). The main path continued to produce mammals (M), including humans.
2 Charles Darwin published his book: "On the Origin of Species by Natural Selection." It included this tree of life as its only image.
2 Ernst Haeckel published his version of a tree of life in his book
"Generelle Morphologie der Organismen." It shows an early division of life forms into three kingdoms: Plantae (all living and extinct plants), Protista (a collection of about 35 simple life forms that are either single-celled or multicelled without specialized tissues) and Animalia (the animal kingdom).
Modern views of the "tree of life" are considerably more complex:
A detailed view:
This images was prepared by David M. Hillis, Derrick Zwickl, and Robin Gutell of the University of Texas. Approximately 3,000 species are included. In spite of its obvious complexity, this image includes only a small fraction (0.18%) of the 1.7 million species of life on earth "... that have been formally described and named."
A tiny portion of a simplified tree of life:
The tree starts at the center of the diagram, with the development of the first, elementary form of life circa 3.5 billion years ago: a single cell. Over time, three groupings of life developed:
- Archaea which are single-celled forms of life similar to bacteria; and
Eukaryotes which consist of one or more complex cells with its genetic material embedded in a nucleus. This led to bananas, fruit flies and humans. 4 People who watch the TV program "The Big Bang Theory" will recall that the character Sheldon Cooper suspects that he is perhaps the first member of a new species, having evolved from ordinary Homo Sapiens.
At about the 2 o'clock position are mammals including everyone reading this web page (unless, of course, some intelligent form of life living in a different planet in another solar system has tapped into the Earth-based Internet).
Mammals are described as:
"A group of tetrapods [four-footed animals] ... with hair covering all or part of their skin; females produce milk to feed their developing young. Includes the prototherians, marsupials, and eutherians." 4
An interactive version of this tree can be found at the Life web site which has much more information available.
The following information sources were used to prepare and update the above
essay. The hyperlinks are not necessarily still active today.
"File: Darwin tree.png," Wikimedia, at: http://commons.wikimedia.org/
"Tree of life (science), Wikipedia, at: http://en.wikipedia.org/
"Tree of Life," University of Texas, undated, at: http://www.zo.utexas.edu/
D. Sadava, D. M. Hillis, H. C. Heller, and M. Berenbaum. "Life: The Science of Biology," W. H. Freeman (2009). Read reviews or order this book safely from Amazon.com online book store
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Consultants on Religious Tolerance.
Copyrights for the individual quotations held by their creators.
Last updated and reviewed: 2016-FEB-12, Darwin Day.
Compiled by: B.A. Robinson